Biaxially oriented polypropylene film for transfer substrates or for thin-film production processes, polypropylene film with release layer, multilayered film for transfer, transfer method, and method for producing thin film

Abstract

Provided is a biaxially oriented polypropylene film for transfer substrates or for thin-film production processes, the film satisfying the following (1), (2), and (3). (1) A propylene resin forming the biaxially oriented polypropylene film for transfer substrates has a mesopentad content of 97.5% or higher. (2) The relationship between the width-direction loop stiffness stress S [mN] and the thickness t (μm) satisfies expression (A).　(A): S≥0.0010×t3. (3) When components of the biaxially oriented polypropylene film are separated into a crystalline component (I), a restrained non-crystalline component (II), and an unrestrained amorphous component (III) by pulse NMR based on a solid echo method, the proportion of the component (III) is 7% or less.

Description

Biaxially oriented polypropylene film for transfer substrate or thin film manufacturing process, release layer laminated polypropylene film, transfer laminated film, transfer method, and thin film manufacturing method

[0001] The present disclosure relates to a biaxially oriented polypropylene film for use as a transfer substrate or in a thin film manufacturing process, a release layer-laminated polypropylene film, a laminated film for transfer, a transfer method, and a method for manufacturing a thin film.

[0002] (Background Art of the First Disclosure) Biaxially oriented polypropylene films are used for industrial purposes such as packaging, release agents, and adhesive tapes, and have also been proposed as substrate films for transfer (e.g., Patent Documents 1 and 2). Compared with biaxially oriented polyethylene terephthalate (PET) films, which are often used as substrate films for transfer, biaxially oriented polypropylene (OPP) films have a smaller specific gravity, which makes film rolls lighter, making them easier to handle, and reducing the energy required for transportation.

[0003] (Background Art of the Second Disclosure) Biaxially oriented polypropylene films are used for industrial purposes such as packaging, release agents, and adhesive tapes, and have also been proposed as substrate films for thin film manufacturing processes (e.g., Patent Document 3). Compared with biaxially oriented polyethylene terephthalate (PET) films, which are often used as substrate films for thin film manufacturing processes, biaxially oriented polypropylene (OPP) films have a smaller specific gravity, which makes film rolls lighter, making them easier to handle, and reducing the energy required for transportation.

[0004] JP 2021-55387 A JP 2019-155655 A JP 2022-100316 A

[0005] (First Problem) Conventional biaxially oriented polypropylene films have poor heat resistance, resulting in poor flatness and dimensional accuracy due to heat applied when providing a transfer layer, and poor transfer accuracy due to heat applied during transfer. Furthermore, due to insufficient rigidity, the biaxially oriented polypropylene film may stretch and wrinkle when strong tension is applied during the provision of a transfer layer, processing, transfer, etc. The first problem is to provide a biaxially oriented polypropylene film for transfer substrates that has excellent rigidity and heat resistance.

[0006] (Second Objective) Conventional biaxially oriented polypropylene films sometimes have insufficient rigidity and poor heat resistance, which can result in poor flatness, quality, and appearance due to heat, for example, when forming a thin film layer. The second object of the present invention is to provide a biaxially oriented polypropylene film for thin film manufacturing processes that has excellent rigidity and heat resistance.

[0007] (First Disclosure) The biaxially oriented polypropylene film for transfer substrate, the release layer-laminated polypropylene film for transfer, the laminated film for transfer, or the transfer method according to the first disclosure is preferably any one of the following [1] to

[13] . This allows the first problem to be solved. [1] A biaxially oriented polypropylene film for transfer substrate that satisfies the following (1), (2), and (3). (1) The polypropylene resin constituting the biaxially oriented polypropylene film for transfer substrate has a mesopentad fraction of 97.5% or more. (2) The relationship between the loop stiffness stress S [mN] in the width direction and the thickness t (μm) satisfies the following formula (A): S≧0.0010×t ３...(A) (3) When the biaxially oriented polypropylene film is separated into a crystalline component (I), a constrained amorphous component (II), and an unconstrained amorphous component (III) by pulse NMR using a solid echo method, the ratio of (III) is 7% or less. [2] The biaxially oriented polypropylene film for transfer substrates according to [1], wherein the heat shrinkage rate of the biaxially oriented polypropylene film for transfer substrates at 150°C is 10% or less in the longitudinal direction and 25% or less in the width direction. [3] The biaxially oriented polypropylene film for transfer substrates according to [1] or [2], wherein the refractive index Ny in the width direction of the biaxially oriented polypropylene film for transfer substrates is 1.5250 or more and ΔNy is 0.0240 or more. [4] The biaxially oriented polypropylene film for transfer substrates according to any of [1] to [3], wherein the haze of the biaxially oriented polypropylene film for transfer substrates is 5.0% or less. [5] The biaxially oriented polypropylene film for transfer substrates according to any one of [1] to [4], wherein the half-width of the peak derived from crystals oriented in the width direction in the azimuth angle dependence of the (110) plane of polypropylene α-crystals obtained by wide-angle X-ray diffraction measurement is 30° or less. [6] The biaxially oriented polypropylene film for transfer substrates according to any one of [1] to [5], wherein the polypropylene resin has a crystallization temperature of 105°C or higher and a melting point of 160°C or higher. [7] The biaxially oriented polypropylene film for transfer substrates according to any one of [1] to [6], wherein the polypropylene resin has a melt flow rate of 4.0 g / 10 min or higher. [8] The biaxially oriented polypropylene film for transfer substrates according to any one of [1] to [7], wherein the polypropylene resin contains 35% by mass or more of components with a molecular weight of 100,000 or less. [9] A release-layer-laminated polypropylene film for transfer, comprising the biaxially oriented polypropylene film for transfer substrates according to any one of [1] to [8], and a release layer laminated on at least one surface of the biaxially oriented polypropylene film for transfer substrates.

[10] A transfer laminate film comprising the biaxially oriented polypropylene film for transfer substrates according to any one of [1] to [8] and a transfer layer.

[11] The transfer laminate film according to

[10] , wherein the transfer layer comprises at least one layer selected from the group consisting of 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, and a rubber sheet layer.

[12] A transfer method comprising the steps of: laminating the transfer laminate film according to

[10] to an object to be transferred; and peeling the biaxially oriented polypropylene film for transfer substrate of the transfer laminate film from the object to which the transfer laminate film has been laminated.

[13] The transfer method according to

[12] , wherein the object to be transferred is paper, film, cloth, wood, glass, ceramics, metal, a resin molded product, or a conductive thin film laminate.

[0008] (Second Disclosure) The biaxially oriented polypropylene film for thin film manufacturing processes and the method for manufacturing thin films according to the second disclosure are preferably any one of the following

[14] to

[26] . This makes it possible to solve the second problem.

[14] A biaxially oriented polypropylene film for thin film manufacturing processes that satisfies the following (1), (2), and (3). (1) The polypropylene resin constituting the biaxially oriented polypropylene film for thin film manufacturing processes has a mesopentad fraction of 97.5% or more. (2) The relationship between the loop stiffness stress S [mN] in the width direction and the thickness t (μm) satisfies the following formula (A): S≧0.0010×t ３...(A) (3) When the film is separated into a crystalline component (I), a constrained amorphous component (II), and an unconstrained amorphous component (III) by pulse NMR using the solid echo method, the ratio of (III) is 7% or less.

[15] The biaxially oriented polypropylene film for thin film manufacturing processes according to

[14] , wherein the heat shrinkage rate of the biaxially oriented polypropylene film for thin film manufacturing processes at 150°C is 10% or less in the longitudinal direction and 25% or less in the width direction.

[16] The biaxially oriented polypropylene film for thin film manufacturing processes according to

[14] or

[15] , wherein the refractive index Ny of the biaxially oriented polypropylene film for thin film manufacturing processes in the width direction is 1.5250 or more and ΔNy is 0.0240 or more.

[17] The biaxially oriented polypropylene film for thin film manufacturing processes according to any of

[14] to

[16] , wherein the haze of the biaxially oriented polypropylene film for thin film manufacturing processes is 5.0% or less.

[18] The biaxially oriented polypropylene film for thin film manufacturing processes according to any one of

[14] to

[17] , wherein the half-width of the peak derived from oriented crystals in the width direction in the azimuth angle dependence of the (110) plane of polypropylene α-crystals obtained by wide-angle X-ray diffraction measurement is 30° or less.

[19] The biaxially oriented polypropylene film for thin film manufacturing processes according to any one of

[14] to

[18] , wherein the polypropylene resin has a crystallization temperature of 105°C or higher and a melting point of 160°C or higher.

[20] The biaxially oriented polypropylene film for thin film manufacturing processes according to any one of

[14] to

[19] , wherein the polypropylene resin has a melt flow rate of 4.0 g / 10 min or higher.

[21] The biaxially oriented polypropylene film for thin film manufacturing processes according to any one of

[14] to

[20] , wherein the polypropylene resin has a content of components with a molecular weight of 100,000 or less of 35% by mass or higher.

[22] A release-layer-laminated biaxially oriented polypropylene film for thin film manufacturing processes, comprising the biaxially oriented polypropylene film for thin film manufacturing processes according to any one of

[14] to

[21] and a release layer laminated on at least one side of the biaxially oriented polypropylene film for thin film manufacturing processes.

[23] A method for producing a thin film, comprising Step 1A of preparing a biaxially oriented polypropylene film for thin film production according to any one of

[14] to

[21] , Step 1B of providing a thin film layer on at least one side of the biaxially oriented polypropylene film for thin film production, and Step 1C of peeling the thin film layer from the biaxially oriented polypropylene film for thin film production.

[24] A method for producing a thin film according to

[23] , wherein the thin film layer comprises any one of a resin film, a polymer electrolyte membrane, and a porous membrane.

[25] A method for producing a thin film, comprising Step 2A of preparing a release layer-laminated biaxially oriented polypropylene film for thin film production according to

[22] , Step 2B of providing a thin film layer on the release layer side of the release layer-laminated biaxially oriented polypropylene film for thin film production, and Step 2C of peeling the thin film layer from the release layer.

[26] A method for producing a thin film according to

[25] , wherein the thin film layer comprises any one of a resin film, a polymer electrolyte membrane, and a porous membrane.

[0009] These disclosures may be combined, specifically the first disclosure and the second disclosure may be combined.

[0010] The first disclosure provides a biaxially oriented polypropylene film for transfer substrates that has excellent rigidity and heat resistance. This allows for wrinkle-free, smooth transfer with high dimensional accuracy. This also makes it possible to reduce the film thickness compared to conventional methods, thereby reducing film waste after use and reducing the environmental impact.

[0011] The second disclosure provides a biaxially oriented polypropylene film for thin film manufacturing processes that has excellent rigidity and heat resistance. This allows for the formation of thin films with excellent flatness, quality, and appearance. This also makes it possible to reduce the film thickness compared to conventional methods, thereby reducing film waste after use and reducing the environmental impact.

[0012] Figure 1 shows １ 1 shows a schematic diagram of component separation of the decay curve of spin-spin relaxation time observed by H-pulse NMR.

[0013] (First Disclosure) Hereinafter, a biaxially oriented polypropylene film for transfer substrate according to an embodiment of the first disclosure will be described. The biaxially oriented polypropylene film for transfer substrate according to the embodiment satisfies the following (1), (2), and (3): (1) The mesopentad fraction of the polypropylene resin constituting the biaxially oriented polypropylene film for transfer substrate is 97.5% or more. (2) The relationship between the loop stiffness stress S [mN] in the width direction and the thickness t (μm) satisfies the following formula (A): S≧0.0010×t ３ ...(A) (3) When separated into a crystalline component (I), a constrained amorphous component (II), and an unconstrained amorphous component (III) as determined by pulsed NMR using the solid echo method, the ratio of (III) is 7% or less.

[0014] The biaxially oriented polypropylene film transfer substrate of the embodiment is preferably 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. This proportion may be 100% by mass or less, or 99% by mass or less. The polypropylene resin composition may contain additives. The additives may include a crystal nucleating agent, an antioxidant, a heat stabilizer, a slip agent, an antistatic agent, an antiblocking agent, a filler, a viscosity modifier, a color inhibitor, or a combination thereof.

[0015] (Polypropylene Resin) The polypropylene resin may contain a polypropylene homopolymer, a copolymer of propylene and ethylene and / or an α-olefin having 4 or more carbon atoms, or a mixture thereof. Of these, a propylene homopolymer that is substantially free of ethylene and / or an α-olefin having 4 or more carbon atoms is preferred. In the case of a copolymer, the amount of ethylene and / or an α-olefin 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, and particularly preferably 0.1 mol% or less, based on 100 mol% of all structural units of the copolymer. Within the above range, crystallinity is likely to be improved. The amount of this component may be 0.01 mol% or more. Examples of the α-olefin component having 4 or more carbon atoms that constitutes such a copolymer include 1-butene, 1-pentene, 3-methylpentene-1, 3-methylbutene-1, 1-hexene, 4-methylpentene-1, 5-ethylhexene-1, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene, etc. The polypropylene resin may contain two or more different polypropylene homopolymers, copolymers with ethylene and / or α-olefins having 4 or more carbon atoms, or mixtures thereof.

[0016] (Stereoregularity) The mesopentad fraction (hereinafter sometimes abbreviated as [mmmm]%) of the polypropylene resin is 13It is quantified based on the peak assignments in a C-NMR spectrum and refers to the proportion of five consecutive propylene monomer units in a polypropylene resin having the same stereostructure, and is an index of stereoregularity. The mesopentad fraction of a polypropylene resin is 97.5% or more, preferably in the range of 97.5 to 99.9%, more preferably in the range of 98.0 to 99.7%, even more preferably in the range of 98.3 to 99.5%, and particularly preferably in the range of 98.5 to 99.3%. A mesopentad fraction of 97.5% or more enhances the crystallinity of the polypropylene resin, improving the melting point, crystallinity, and crystalline orientation of the crystals in the film, and making it easier to achieve rigidity and heat resistance at high temperatures. A mesopentad fraction of 99.9% or less facilitates cost reduction in polypropylene production and reduces breakage during film formation. The mesopentad fraction is measured by nuclear magnetic resonance (NMR). A mesopentad fraction of 99.5% or less is even more preferable. In order to set the mesopentad fraction of the polypropylene resin within the above range, a method of washing the obtained polypropylene resin powder with a solvent such as n-heptane, a method of appropriately selecting a catalyst and / or a co-catalyst, and a method of appropriately selecting the components of the polypropylene resin composition are preferably employed.

[0017] (Melting temperature) The melting temperature (Tm) of the polypropylene resin constituting the biaxially oriented polypropylene film for transfer substrates, measured by DSC, i.e., the lower limit of the melting point, is preferably 160 ° C, more preferably 161 ° C, even more preferably 162 ° C, still more preferably 163 ° C, and particularly preferably 164 ° C. When Tm is 160 ° C or higher, rigidity and heat resistance at high temperatures are easily obtained. The upper limit of Tm is preferably 170 ° C, more preferably 169 ° C, even more preferably 168 ° C, still more preferably 167 ° C, and particularly preferably 166 ° C. When Tm 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. The melting temperature can also be further increased by blending a nucleating agent with the polypropylene resin. Tm is the main endothermic peak temperature associated with melting, which is observed when 1 to 10 mg of a sample is packed into an aluminum pan and set in a differential scanning calorimeter (DSC), melted at 230°C for 5 minutes in a nitrogen atmosphere, cooled to 30°C at a scanning rate of -10°C / min, held for 5 minutes, and then heated again at a scanning rate of 10°C / min.

[0018] (Crystallization temperature) The lower limit of the crystallization temperature (Tc) of the polypropylene resin constituting the biaxially oriented polypropylene film for transfer substrate, as measured by DSC, is preferably 105 ° C, more preferably 108 ° C, and even more preferably 110 ° C. If Tc is 105 ° C or higher, crystallization is likely to proceed during width direction stretching and the subsequent cooling process, making it easier to obtain rigidity and heat resistance at high temperatures. The upper limit of Tc is preferably 135 ° C, more preferably 133 ° C, even more preferably 132 ° C, even more preferably 130 ° C, particularly preferably 128 ° C, and most preferably 127 ° C. If Tc is 135 ° C or lower, it is difficult to increase the cost of polypropylene production and it is difficult to break during film formation. The crystallization temperature can also be further increased by blending a crystal nucleating agent into the polypropylene resin. Tc is the main peak temperature of the exothermic peak observed when 1 to 10 mg of a sample is packed into an aluminum pan, set in a DSC, melted at 230°C for 5 minutes in a nitrogen atmosphere, and cooled to 30°C at a scanning rate of -10°C / min.

[0019] (Melt Flow Rate) The melt flow rate (MFR) of the polypropylene resin constituting the biaxially oriented polypropylene film for transfer substrate, 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, particularly preferably 5.0 to 20 g / 10 min, and most preferably 6.0 to 18 g / 10 min. When the melt flow rate (MFR) of the polypropylene resin is 4.0 g / 10 min or more, it is easy to obtain a biaxially oriented polypropylene film for transfer substrate with low thermal shrinkage. Furthermore, when the melt flow rate (MFR) of the polypropylene resin is 30 g / 10 min or less, it is easy to maintain the film formability of the film.

[0020] From the viewpoint of film properties, the lower limit of the melt flow rate (MFR) (230°C, 2.16 kgf) of the polypropylene resin constituting the film is preferably 5.0 g / 10 min, 5.5 g / 10 min, 6.0 g / 10 min, 6.3 g / 10 min, 6.5 g / 10 min, 6.8 g / 10 min, and 7.0 g / 10 min, in that order. When the melt flow rate (MFR) of the polypropylene resin is 5.0 g / 10 min or higher, the amount of low molecular weight components in the polypropylene resin constituting the film increases. If a polypropylene resin containing a large amount of such low molecular weight components is used and a width direction stretching step in the film formation process described below is adopted, the oriented crystallization of the polypropylene resin is further promoted, the crystallinity of the film is more likely to be increased, and in addition, the entanglement of polypropylene molecular chains in the amorphous portion is reduced, which makes it easier to improve heat resistance. In order to set the melt flow rate (MFR) of the polypropylene resin within the above range, it is preferable to employ a method for controlling the average molecular weight or molecular weight distribution of the polypropylene resin.

[0021] That is, the lower limit of the amount of components having a molecular weight of 100,000 or less in the GPC cumulative curve of the polypropylene resin constituting the biaxially oriented polypropylene film for transfer substrates is preferably 35% by mass, more preferably 38% by mass, even more preferably 40% by mass, even more preferably 41% by mass, and particularly preferably 42% by mass. The upper limit of the amount of components having a molecular weight of 100,000 or less in the GPC cumulative curve is preferably 65% ​​by mass, more preferably 60% by mass, and even more preferably 58% by mass. When the amount of components having a molecular weight of 100,000 or less in the GPC cumulative curve is 65% by mass or less, the film strength is less likely to decrease. In this case, if the polypropylene resin contains high-molecular-weight components or long-chain branched components with long relaxation times, the amount of components having a molecular weight of 100,000 or less contained in the polypropylene resin can be easily adjusted without significantly changing the overall viscosity, which makes it easier to improve film formability without significantly affecting rigidity or thermal shrinkage.

[0022] (Molecular weight distribution) The polypropylene resin has a lower limit of the mass average molecular weight (Mw) / number average molecular weight (Mn), which is an index of the breadth of the molecular weight distribution, of preferably 3.5, more preferably 4, even more preferably 4.5, and particularly preferably 5. The upper limit of Mw / Mn is preferably 30, more preferably 25, even more preferably 23, particularly preferably 21, and most preferably 20. Mw / Mn can be obtained using gel permeation chromatography (GPC). When Mw / Mn is in the above range, it is easy to increase the amount of components having a molecular weight of 100,000 or less.

[0023] The molecular weight distribution of the polypropylene resin can be adjusted by polymerizing components of different molecular weights in a series of plants in multiple stages, blending components of different molecular weights offline in a kneader, polymerizing by blending catalysts with different performances, or using a catalyst that can achieve a desired molecular weight distribution. The shape of the molecular weight distribution obtained by GPC may be a gentle molecular weight distribution with a single peak in a GPC chart with the logarithm (log M) of the molecular weight (M) on the horizontal axis and the differential distribution value (weight fraction per log M) on the vertical axis, or may be a molecular weight distribution with multiple peaks or shoulders.

[0024] (Film Thickness) The thickness of the biaxially oriented polypropylene film for transfer substrates is set according to each application, but to obtain film strength, the lower limit of the film thickness is preferably 5 μm, more preferably 8 μm, even more preferably 10 μm, particularly preferably 12 μm, and most preferably 14 μm. A film thickness of 5 μm or more makes it easier to obtain rigidity in the film, facilitates the formation of a transfer layer, and facilitates peeling during transfer. Furthermore, wrinkles are less likely to occur when wound up. The upper limit of the film thickness is preferably 120 μm, more preferably 100 μm, even more preferably 80 μm, particularly preferably 70 μm, and most preferably 60 μm. A film thickness of 120 μm or less is less likely to reduce the cooling rate of the unstretched sheet during the extrusion process. Biaxially oriented polypropylene films for transfer substrates are typically produced as rolls with a width of approximately 2,000 to 12,000 mm and a length of approximately 1,000 to 50,000 m, and then wound up into a film roll. Furthermore, it is slit according to the application and supplied as a slit roll with a width of 300 to 2000 mm and a length of 500 to 5000 m. It is possible to obtain a longer film roll of the biaxially oriented polypropylene film for transfer substrates.

[0025] (Thickness Uniformity) The lower limit of the thickness uniformity of the biaxially oriented polypropylene film for transfer substrate is preferably 0%, more preferably 0.1%, even more preferably 0.5%, and particularly preferably 1%. The upper limit of the thickness uniformity is preferably 20%, more preferably 17%, even more preferably 15%, particularly preferably 12%, and most preferably 10%. Within the above range, defects are less likely to occur during post-processing such as coating or printing, making it suitable for applications requiring precision. The thickness uniformity can be measured, for example, as follows. A test piece 40 mm in width is cut from a steady region where the film properties are stable in the length direction of the film, and the film thickness is measured continuously over 20,000 mm using a film feeder manufactured by Micron Measuring Instruments Co., Ltd. (product number: A90172) and a continuous film thickness measuring instrument manufactured by Anritsu Corporation (product name: K-313A wide-range high-sensitivity electronic micrometer). Furthermore, the maximum, minimum, and average thickness values ​​are determined, and the thickness uniformity can be calculated using the following formula. Thickness uniformity (%) = [(maximum thickness - minimum thickness) / average thickness] x 100

[0026] (Film characteristics) The biaxially oriented polypropylene film for transfer substrate preferably has the following characteristics and structure. Here, the "longitudinal direction" of the biaxially oriented polypropylene film for transfer substrate is the direction corresponding to the flow direction in the film production process, and the "width direction" is the direction perpendicular to the flow direction in the film production process. For polypropylene films whose flow direction in the film production process is unknown, wide-angle X-rays are incident perpendicular to the film surface, and scattering peaks derived from the (110) plane of the α-crystals are scanned in the circumferential direction, and the direction with the greatest diffraction intensity in the obtained diffraction intensity distribution is defined as the "longitudinal direction," and the direction perpendicular to that is defined as the "width direction."

[0027] (Crystalline component (I), constrained amorphous component (II), unconstrained amorphous component (III) determined by pulsed NMR) １It is known that the decay time constant of the FID (Free Induction Decay) of the spin-spin relaxation time T2 observed by H-pulse NMR is observed as the sum of two or more decay time constants. For example, according to Polymer Journal, Vol. 3, No. 4, pp. 448-462 (1972), the decay time constant of the relaxation time of a crystalline polymer is analyzed by the solid echo method of pulse NMR as the sum of the three components: the crystalline component, the mesophase component, and the amorphous component. １ The spin-spin relaxation time T2 observed by H-pulse NMR becomes slower in the order of crystalline, mesophase, and amorphous. The mesophase has a faster T2 than the amorphous phase, and is considered to be an amorphous phase with restricted mobility. When stretching is performed while disentangling the molecular chains, a crystalline component (I) with strong orientation is generated, and an amorphous chain component (II) with restricted mobility (corresponding to the mesophase) is generated near the crystal. On the other hand, when entanglement is high and a disordered orientation is achieved during stretching, an amorphous component (III) (corresponding to the amorphous component) that is not restricted by the crystal is likely to be generated. The unrestricted amorphous component (III) has high mobility and is likely to move to relieve strain at high temperatures, which is thought to be the cause of shrinkage at high temperatures. On the other hand, the restricted amorphous chain (II) is considered to be less likely to shrink at high temperatures because its movement is suppressed even at high temperatures compared to the amorphous component (III).

[0028] The upper limit of the ratio of the unconstrained amorphous component (III) of the biaxially oriented polypropylene film for transfer substrates determined by pulse NMR is preferably 7%, more preferably 6%, and even more preferably 5%. In order to reduce the ratio of the unconstrained amorphous component (III), it is particularly effective to increase the area ratio during film formation and, after sequential biaxial stretching, to perform re-stretching in the width direction at a high temperature. It is also effective to use a polypropylene raw material with a high mesopentad fraction. Furthermore, when measuring the gel permeation chromatography (GPC) integration curve of the polypropylene resin constituting the film, it is effective to set the lower limit of the amount of components with a molecular weight of 100,000 or less to 35% by mass. A ratio of the unconstrained amorphous component (III) determined by pulse NMR of 7% or less means that there are few molecular chains with large distortions in molecular orientation restrained by entanglement points, and the film is less likely to shrink even when crystal melting begins. As a result, even when the release layer or transfer layer is dried at high temperatures, when the transfer layer is heat-treated, or when heat is applied during transfer, the film is less likely to wrinkle, and is less susceptible to dimensional change, curling, and deterioration of flatness.

[0029] When the ratio of the unconstrained amorphous component (III) exceeds 7% when the film is separated into the crystalline component (I), the constrained amorphous component (II), and the unconstrained amorphous component (III) as determined by pulse NMR using the solid echo method, there are many molecular chains with large distortions in the molecular orientation constrained by entanglement points, and therefore shrinkage occurs simultaneously with the start of crystal melting, resulting in a film prone to wrinkles, dimensional changes, curling, and deterioration of flatness. The lower limit of the ratio of the unconstrained amorphous component (III) is not particularly limited, but a practical value is 0.1% or more. If the ratio of the unconstrained amorphous component (III) is attempted to be less than 0.1%, it is necessary to further stretch the film in the width direction at a higher temperature after the sequential biaxial stretching, which may reduce the tension during stretching due to melting, resulting in breakage. Furthermore, the crystalline orientation in the film may be weakened, resulting in reduced rigidity.

[0030] (Heat shrinkage rate at 150°C) The upper limit of the heat shrinkage rate in the longitudinal direction of the biaxially oriented polypropylene film for transfer substrate at 150°C is preferably 10%, more preferably 8.0%, even more preferably 6.0%, particularly preferably 5.0%, and most preferably 4.0%. The lower limit may be 0%, 1.0%, or 2.0%. The upper limit of the heat shrinkage rate in the width direction at 150°C is preferably 25%, more preferably 20%, even more preferably 16%, even more preferably 15%, particularly preferably 12%, and most preferably 10%. The lower limit may be 0%, 2.0%, or 4.0%. When the longitudinal heat shrinkage rate is 10% or less and the widthwise heat shrinkage rate is 25% or less, wrinkles, dimensional changes, and deterioration of flatness of the film or laminate are less likely to occur during release processing, transfer layer processing such as providing a transfer layer or heat treatment, and during heating for transfer. In particular, when the longitudinal heat shrinkage rate at 150°C is 8.0% or less and the widthwise heat shrinkage rate at 150°C is 15% or less, the control range of the roll tension during processing is further expanded, resulting in less wrinkles, dimensional changes, and deterioration of flatness, which is preferable. In addition, because the film shrinks less, uneven release properties and uneven transfer layer characteristics due to uneven heating are less likely to occur. To reduce the heat shrinkage rate at 150°C, it is effective to set the lower limit of the amount of components with a molecular weight of 100,000 or less to 35% by mass when measuring the gel permeation chromatography (GPC) integrated curve of the polypropylene resin constituting the film.

[0031] (F5: stress at 5% elongation at 23 ° C.) The lower limit of the stress (F5) at 5% elongation in the width direction of the biaxially oriented polypropylene film for transfer substrate at 23 ° C. is preferably 110 MPa, more preferably 120 MPa, even more preferably 140 MPa, still more preferably 160 MPa, particularly preferably 180 MPa, and most preferably 190 MPa. The upper limit of F5 in the width direction at 23 ° C. is preferably 300 MPa, more preferably 290 MPa, and even more preferably 280 Pa. If it is 280 MPa or less, practical production is easy and the length-width balance is likely to be improved.

[0032] The lower limit of F5 in the longitudinal direction of the biaxially oriented polypropylene film for transfer substrates at 23°C is preferably 40 MPa, more preferably 42 MPa, even more preferably 46 MPa, and particularly preferably 48 MPa. The upper limit of F5 in the longitudinal direction at 23°C is preferably 70 MPa, more preferably 65 MPa, even more preferably 62 MPa, and particularly preferably 60 MPa. At 70 MPa or less, practical production becomes easier and the length-width balance tends to improve. By setting F5 at the above level or higher, the high rigidity not only makes it easier to maintain the film shape and facilitates release processing, but also makes handling easier during processing and transfer of the transfer layer, and prevents dimensional change and deterioration of flatness, facilitating high-quality, high-precision transfer processing. In addition, smooth peeling during transfer is facilitated. F5 can be kept within the range by adjusting the stretch ratio and relaxation rate, or adjusting the temperature during film formation.

[0033] The widthwise heat shrinkage (%) at 150°C and the widthwise stress at 5% elongation (MPa) at 23°C of the biaxially oriented polypropylene film for transfer substrates preferably satisfy the following formula: Stress at 5% elongation in the widthwise direction at 23°C (MPa) ≥ Widthwise heat shrinkage (%) at 150°C × 4.0 + 140. This results in higher rigidity and a smaller heat shrinkage at high temperatures, making it easier to maintain the shape of the film and reducing the occurrence of wrinkles in the film due to heat during the drying process of the release layer. Furthermore, during release processing, transfer layer processing such as providing a transfer layer or heat treatment, and heating during transfer, the film or laminate is less likely to wrinkle, change in dimension, or deteriorate in flatness, making it easier to handle and facilitating high-quality, high-precision transfer. Wrinkles are caused by heat-induced film shrinkage and film deformation due to tension during roll transport, and optimizing the balance between these two factors can reduce wrinkle occurrence. In addition, the control range of the roll tension during processing is wider, which results in less wrinkling, dimensional changes, and deterioration of flatness, which is preferable. Furthermore, it becomes possible to make the film for transfer substrate thinner, which also contributes to reducing the volume of the release film.

[0034] Furthermore, it is preferable that the heat shrinkage (%) in the width direction at 150°C and the stress (MPa) at 5% elongation in the width direction at 23°C of the biaxially oriented polypropylene film for transfer substrate satisfy the following formula: Stress (MPa) at 5% elongation in the width direction at 23°C ≥ Heat shrinkage (%) in the width direction at 150°C × 4.0 + 150

[0035] Furthermore, it is more preferable that the heat shrinkage (%) in the width direction at 150°C and the stress (MPa) at 5% elongation in the width direction at 23°C of the biaxially oriented polypropylene film for transfer substrate satisfy the following formula: Stress (MPa) at 5% elongation in the width direction at 23°C ≥ Heat shrinkage (%) in the width direction at 150°C × 4.0 + 160

[0036] (Heat shrinkage at 120 ° C) The upper limit of the longitudinal heat shrinkage at 120 ° C of the biaxially oriented polypropylene film for transfer substrate is preferably 2.0%, more preferably 1.5%, even more preferably 1.2%, particularly preferably 1.0%, and most preferably 0.8%. The lower limit may be 0% or 0.1%. If it is 2.0% or less, poor appearance such as vertical streaks is less likely to occur during release processing and processing of the transfer layer. The upper limit of the widthwise heat shrinkage at 120 ° C is preferably 8.0%, more preferably 5.0%, even more preferably 3.5%, even more preferably 2.5%, particularly preferably 2.0%, even more particularly preferably 1.5%, and most preferably 1.0%. The lower limit may be 0%, 0.1%, or 0.2%. When the heat shrinkage ratio is within the above range, the polypropylene film or laminated film is less likely to wrinkle, change in dimension, or deteriorate in flatness during release processing, processing of the transfer layer, or heating for transfer, making it easier to perform high-quality, high-precision transfer. The heat shrinkage ratio at 120°C can be kept within the range by adjusting the stretching ratio, stretching temperature, and heat setting temperature.

[0037] The widthwise heat shrinkage (%) at 120°C and widthwise tensile modulus (GPa) at 23°C of the biaxially oriented polypropylene film for transfer substrates preferably satisfy the following formula: Widthwise tensile modulus (GPa) at 23°C ≥ Widthwise heat shrinkage (%) at 120°C × 0.3 + 7.0. This results in higher rigidity and a smaller heat shrinkage at high temperatures, making it less likely for the film or laminate to wrinkle, change in size, or lose its flatness during release processing, transfer layer processing such as providing a transfer layer or heat treatment, or heating during transfer. This also makes handling easier, facilitating high-quality, high-precision transfer. Furthermore, smooth peeling is also facilitated.

[0038] It is more preferable that the heat shrinkage (%) in the width direction at 120°C and the tensile modulus (GPa) in the width direction at 23°C of the biaxially oriented polypropylene film for transfer substrate satisfy the following formula: tensile modulus (GPa) in the width direction at 23°C ≥ heat shrinkage (%) in the width direction at 120°C × 0.3 + 8.0

[0039] Furthermore, it is more preferable that the heat shrinkage (%) in the width direction at 120°C and the tensile modulus (GPa) in the width direction at 23°C of the biaxially oriented polypropylene film for transfer substrate satisfy the following formula: tensile modulus (GPa) in the width direction at 23°C ≥ heat shrinkage (%) in the width direction at 120°C × 0.3 + 9.0

[0040] (Tensile modulus at 23 ° C.) The lower limit of the longitudinal tensile modulus of the biaxially oriented polypropylene film for transfer substrate at 23 ° C. is preferably 2.0 GPa, more preferably 2.1 GPa, even more preferably 2.2 GPa, still more preferably 2.3 GPa, particularly preferably 2.4 GPa, and most preferably 2.6 GPa. The upper limit of the longitudinal tensile modulus is preferably 4.0 GPa, more preferably 3.8 GPa, even more preferably 3.7 GPa, particularly preferably 3.6 GPa, and most preferably 3.5 GPa. At 4.0 GPa or less, practical production is easy and the balance of the longitudinal and widthwise properties is easily improved.

[0041] The lower limit of the widthwise tensile modulus of the biaxially oriented polypropylene film for transfer substrates at 23°C is preferably 5.0 GPa, more preferably 6.0 GPa, even more preferably 6.5 GPa, even more preferably 6.7 GPa, particularly preferably 7.0 GPa, even more particularly preferably 8.0 GPa, and most preferably 8.5 GPa. The upper limit of the widthwise tensile modulus is preferably 15 GPa, more preferably 13 GPa, and even more preferably 12 GPa. A modulus of 15 GPa or less facilitates practical manufacturing and improves the balance of longitudinal and widthwise properties. By setting the tensile modulus at the above level or higher, the film shape is easily maintained and it is less likely to stretch even when strong tension is applied to the film when providing a transfer layer, processing, or transferring. This makes it easier to handle during processing and transferring the transfer layer, and the film or laminate is less likely to wrinkle, change in size, or deteriorate in flatness, facilitating high-quality, high-precision transfer. Furthermore, smooth peeling is easily achieved during transfer. The tensile modulus can be kept within the range by adjusting the stretching ratio and relaxation rate, or by adjusting the temperature during film formation.

[0042] (Tensile breaking strength at 23°C) The lower limit of the longitudinal tensile breaking strength of the biaxially oriented polypropylene film for transfer substrate at 23°C is preferably 90 MPa, more preferably 100 MPa, even more preferably 110 MPa, and particularly preferably 115 MPa. If it is 90 MPa or more, wrinkles are less likely to occur during release film processing, and film breakage is less likely to occur during release processing. The upper limit of the longitudinal tensile breaking strength is preferably 200 MPa as a practical value, more preferably 180 MPa, and even more preferably 160 MPa. If it is 200 MPa or less, film breakage is less likely.

[0043] The lower limit of the widthwise tensile breaking strength of the biaxially oriented polypropylene film for transfer substrates at 23°C is preferably 250 MPa, more preferably 300 MPa, even more preferably 350 MPa, even more preferably 400 MPa, particularly preferably 420 MPa, even more particularly preferably 440 MPa, and most preferably 450 MPa. The upper limit of the widthwise tensile breaking strength is preferably 650 MPa as a practical value, more preferably 600 MPa, and even more preferably 550 MPa. At 650 MPa or less, film breakage is likely to be reduced. At a tensile breaking strength of 650 MPa or more, strong tension is easily applied to the film when providing a transfer layer, during processing, or during transfer, which makes it less likely for the film or laminate to wrinkle, change in dimension, or deteriorate in flatness, making handling easier and facilitating high-quality, high-precision transfer. Furthermore, film breakage is less likely to occur during release processing. The tensile breaking strength can be kept within the range by adjusting the stretch ratio, stretching temperature, and heat setting temperature.

[0044] (Tensile elongation at break at 23°C) The lower limit of the longitudinal tensile elongation at break of the biaxially oriented polypropylene film for transfer substrate at 23°C is preferably 150%, more preferably 180%, even more preferably 190%, particularly preferably 200%, and most preferably 210%. If it is 150% or more, the film tends to break less. The upper limit of the longitudinal tensile elongation at break at 23°C is preferably 300% as a practical value, more preferably 280%.

[0045] The lower limit of the tensile elongation at break in the width direction of the biaxially oriented polypropylene film for transfer substrates at 23°C is preferably 15%, more preferably 20%, even more preferably 25%, and particularly preferably 30%. If it is 15% or more, the film is less likely to break. The upper limit of the tensile elongation at break in the width direction at 23°C is preferably 60%, more preferably 55%, and even more preferably 50%. The tensile elongation at break can be kept within the range by adjusting the stretch ratio, stretching temperature, and heat setting temperature.

[0046] (Refractive Index) The lower limit of the refractive index (Nx) in the longitudinal direction of the biaxially oriented polypropylene film for transfer substrate is preferably 1.4950, more preferably 1.4970, even more preferably 1.4980, particularly preferably 1.4990, and most preferably 1.5000. If it is 1.4950 or higher, the rigidity of the film is easily increased. The upper limit of the refractive index (Nx) in the longitudinal direction is preferably 1.5100, more preferably 1.5070, and even more preferably 1.5050. If it is 1.5100 or lower, the balance of the properties in the longitudinal direction and the width direction of the film is easily excellent. The lower limit of the refractive index (Ny) in the width direction of the biaxially oriented polypropylene film for transfer substrate is preferably 1.5250, more preferably 1.5253, even more preferably 1.5255, even more preferably 1.5260, and particularly preferably 1.5265. If it is 1.5250 or higher, the rigidity of the film is easily increased. The upper limit of the refractive index (Ny) in the width direction is preferably 1.5280, more preferably 1.5275, and even more preferably 1.5270. If it is 1.5280 or less, the film tends to have an excellent balance of properties in the longitudinal direction and width direction.

[0047] The lower limit of the refractive index (Nz) in the thickness direction of the biaxially oriented polypropylene film for transfer substrate is preferably 1.4960, more preferably 1.4965, even more preferably 1.4970, particularly preferably 1.4980, and most preferably 1.4990. If it is 1.4960 or higher, the rigidity of the film is likely to be increased. The upper limit of the refractive index (Nz) in the thickness direction is preferably 1.5020, more preferably 1.5015, and even more preferably 1.5010. If it is 1.5020 or lower, the heat resistance of the film is likely to be increased. The refractive index can be kept within the range by adjusting the stretching ratio, stretching temperature, and heat setting temperature.

[0048] (ΔNy) The lower limit of ΔNy of the biaxially oriented polypropylene film for transfer substrate is preferably 0.0240, more preferably 0.0245, even more preferably 0.0247, even more preferably 0.0250, particularly preferably 0.0255, and most preferably 0.0260. If it is 0.0240 or higher, the rigidity of the film tends to be high. The upper limit of ΔNy is preferably 0.0280 as a practical value, more preferably 0.0277, even more preferably 0.0273, and particularly preferably 0.0270. If it is 0.0280 or lower, thickness unevenness tends to be improved. ΔNy can be kept within the range by adjusting the film stretch ratio, stretching temperature, and heat setting temperature. ΔNy is calculated using the following formula, where Nx, Ny, and Nz are the refractive indices along the longitudinal, width, and thickness directions of the film, respectively, and means the degree of widthwise orientation in the overall orientation of the film in the longitudinal, width, and thickness directions. △Ny=Ny-[(Nx+Nz) / 2]

[0049] (Plane Orientation Coefficient) The lower limit of the plane orientation coefficient (ΔP) of the biaxially oriented polypropylene film for transfer substrate is preferably 0.0135, more preferably 0.0138, and even more preferably 0.0140. If it is 0.0135 or higher, the balance in the plane direction of the film is good and thickness unevenness is also good. The upper limit of the plane orientation coefficient (ΔP) is preferably 0.0155 as a practical value, more preferably 0.0152, and even more preferably 0.0150. If it is 0.0155 or lower, it tends to have excellent heat resistance at high temperatures. The plane orientation coefficient (ΔP) can be kept within the range by adjusting the stretch ratio, stretching temperature, and heat setting temperature. The plane orientation coefficient (ΔP) is calculated using the formula [(Nx + Ny) / 2] - Nz.

[0050] (Average Refractive Index) The lower limit of the average refractive index of the biaxially oriented polypropylene film for transfer substrate is preferably 1.5080, more preferably 1.5081, even more preferably 1.5082, particularly preferably 1.5083, and most preferably 1.5090. The upper limit of the average refractive index is preferably 1.5150, more preferably 1.5140, even more preferably 1.5135, and particularly preferably 1.5130, as a practical value. A refractive index of 1.5080 or higher makes the film or laminate less susceptible to wrinkling, dimensional changes, and deterioration of flatness during release processing, transfer layer processing such as providing a transfer layer or heat treatment, and heating during transfer, thereby making handling easier and facilitating high-quality, high-precision transfer. The average refractive index can be kept within this range by adjusting the film stretch ratio, stretching temperature, and heat setting temperature. The average refractive index is calculated using the following formula, where Nx, Ny, and Nz are the refractive indices along the longitudinal, width, and thickness directions of the film, respectively. Average refractive index=(Nx+Ny+Nz) / 3

[0051] (Haze) When transparency is required for the biaxially oriented polypropylene film for transfer substrates, the upper limit of the film haze is preferably 5.0%, more preferably 4.5%, even more preferably 4.0%, particularly preferably 3.5%, and most preferably 3.0%. A haze of 5.0% or less is easy to use in applications requiring transparency. The lower limit of the haze is preferably 0.1%, more preferably 0.2%, even more preferably 0.3%, and particularly preferably 0.4% as a practical value. A haze of 0.1% or more is easy to manufacture. The haze can be kept within the range by adjusting the chill roll (CR) temperature, width direction stretching temperature, tenter preheating temperature before width direction stretching, width direction stretching temperature, or heat setting temperature, or the amount of components of the polypropylene resin with a molecular weight of 100,000 or less, but may increase by adding an antiblocking agent or providing a sealing layer.

[0052] (Half width of diffraction peak derived from oriented crystals) In the azimuth angle dependence of the scattering peak of the (110) plane of polypropylene α-crystals obtained by wide-angle X-ray measurement perpendicular to the film surface of a biaxially oriented polypropylene film for transfer substrate, the upper limit of the half width (Wh) of the diffraction peak derived from the oriented crystals in the width direction of the film is preferably 30 °, more preferably 28 °, even more preferably 26 °, even more preferably 25 °, particularly preferably 24 °, more particularly preferably 23 °, and most preferably 22.0 °. When the half width (Wh) is 30 ° or less, particularly 26 ° or less, the rigidity of the film is easily increased. The lower limit of Wh is preferably 15 °, more preferably 16 °, and even more preferably 17 °.

[0053] (X-ray orientation degree) The lower limit of the X-ray orientation degree calculated from the half-width (Wh) of the biaxially oriented polypropylene film for transfer substrate using the following formula is preferably 0.833, more preferably 0.844, even more preferably 0.856, even more preferably 0.861, particularly preferably 0.867, even more particularly preferably 0.872, and most preferably 0.878. By making it 0.833 or more, especially 0.856 or more, rigidity is easily increased. X-ray orientation degree = (180 - Wh) / 180 The upper limit of the X-ray orientation degree is preferably 0.917, more preferably 0.911, and even more preferably 0.906. By making it 0.917 or less, film formation is easily stabilized.

[0054] (Loop stiffness stress) In a biaxially oriented polypropylene film for transfer substrates, the relationship between the widthwise loop stiffness stress S [mN] and the thickness t (μm) satisfies the following formula (A). In other words, as in the examples described below, when the cube of the thickness t (μm) is plotted on the horizontal axis and the widthwise loop stiffness stress S [mN] on the vertical axis, and linear approximation is performed by the least squares method so that the intercept is 0, and the slope a of the approximated line is determined, the slope a is 0.0010 or more. The loop stiffness stress is an index representing the stiffness of a film, and although it also depends on the thickness of the film, the value of the slope a of the approximated line means a characteristic value specific to the film that is independent of the thickness that determines the rigidity. S≧0.0010×t ３ ...(A)

[0055] The lower limit of the loop stiffness stress S (mN) in the width direction of the biaxially oriented polypropylene film for transfer substrate at 23°C is 0.0010 x t (μm), where t is the thickness of the biaxially oriented polypropylene film. ３ and preferably 0.0011 × t ３ and particularly preferably 0.0012 × t ３ and most preferably 0.0013 × t ３ 0.0010 x t ３ If the film has a thickness of 1 / 2 mm or more, the peeling force during the transfer step is likely to be small, allowing for smooth peeling and preventing peel marks (streaky marks that occur when the film is caught during peeling). The peeling force during the transfer step is likely to be small, allowing for smooth peeling and preventing peel marks (streaky marks that occur when the film is caught during peeling). Furthermore, since the film has high rigidity, wrinkles, dimensional changes, and deterioration of flatness are unlikely to occur in the film or laminate during release processing and processing of the transfer layer, making handling easier and facilitating high-quality, high-precision transfer. The upper limit of the loop stiffness stress S (mN) in the width direction at 23°C is preferably 0.0020 x t ３ and more preferably 0.0019 × t ３ and more preferably 0.0018 × t ３ and particularly preferably 0.0017 × t ３ 0.0020 x t ３ If it is less than this, it is easy to manufacture in practice.

[0056] It is preferable that the relationship between the longitudinal loop stiffness stress S [mN] and the thickness t (μm) of the biaxially oriented polypropylene film for transfer substrates satisfies the following formula (B). In other words, as in the examples described later, when the cube of the thickness t (μm) is plotted on the horizontal axis and the longitudinal loop stiffness stress [mN] on the vertical axis, and linear approximation is performed using the least squares method so that the intercept is 0, and the slope a of the approximated line is determined, it is preferable that the slope a is 0.00030 or more. The following formula (B) will be explained below. S≧0.00030×t ３ ...(B)

[0057] The lower limit of the longitudinal loop stiffness stress S (mN) of the biaxially oriented polypropylene film for transfer substrate at 23° C. is preferably 0.00030×t ３ and more preferably 0.00040 × t ３ and more preferably 0.00045 × t ３ and particularly preferably 0.00048 × t ３ and most preferably 0.00050 × t ３ 0.00030 x t ３ If the film has a thickness of 1 / 2 mm or more, the peeling force during the transfer step is likely to be small, allowing for smooth peeling and preventing peel marks (streaky marks that occur when the film is caught during peeling). Furthermore, since the film has high rigidity, the film and laminate are less likely to develop wrinkles, dimensional changes, or deterioration in flatness during release processing or transfer layer processing, making handling easier and facilitating high-quality, high-precision transfer. The upper limit of the longitudinal loop stiffness stress S (mN) at 23°C is preferably 0.00080 x t ３ and more preferably 0.00075 × t ３ and more preferably 0.00072 × t ３ and particularly preferably 0.00070 × t ３ 0.00080 x t ３ If it is less than this, it is easy to manufacture in practice.

[0058] (Method for producing biaxially oriented polypropylene film for transfer substrate) The biaxially oriented polypropylene film for transfer substrate is preferably obtained by producing an unstretched sheet made of a polypropylene resin composition containing the above-mentioned polypropylene resin as a main component, and biaxially stretching the sheet. As the biaxial stretching method, any of inflation simultaneous biaxial stretching method, tenter simultaneous biaxial stretching method, and tenter sequential biaxial stretching method can be used, but from the viewpoint of film formation stability and thickness uniformity, it is preferable to adopt tenter sequential biaxial stretching method. In particular, it is preferable to stretch in the longitudinal direction and then in the width direction, but a method in which stretching in the width direction and then in the longitudinal direction may also be used.

[0059] Next, a method for producing a biaxially oriented polypropylene film for transfer substrates according to an embodiment will be described below, but the method is not necessarily limited thereto. The biaxially oriented polypropylene film for transfer substrates according to an embodiment may have a layer having another function laminated on at least one side. Lamination may be performed on one or both sides. In this case, the resin composition of the other layer or the central layer may be the polypropylene resin composition described above. Furthermore, the polypropylene resin composition may be different from the polypropylene resin composition described above. The number of layers to be laminated may be one, two, or three or more per side. From a manufacturing standpoint, one or two layers per side is preferred. Preferred lamination methods include, for example, coextrusion using a feed block system or a multi-manifold system. In particular, to improve the handleability of the biaxially oriented polypropylene film for transfer substrates, a resin layer having easy lubricity containing particles or a resin layer having releasability may be laminated to a degree that does not impair the properties. Furthermore, to adjust the releasability, one or both sides may be subjected to corona treatment.

[0060] The following describes an example of a single layer film, in which the tenter sequential biaxial stretching method is used. First, a resin composition containing a polypropylene resin is heated and melted in a single-screw or twin-screw extruder, extruded into a sheet from a T-die, and then cooled and solidified by being placed on a cooling roll. To promote solidification, it is preferable to further cool the sheet cooled by the cooling roll by, for example, immersing it in a water bath.

[0061] Next, the 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.

[0062] Subsequently, the uniaxially stretched film is preheated and then stretched in the width direction at a specific temperature while holding the film edges in a tenter-type stretching machine to obtain a biaxially stretched film. This width direction stretching step will be described in detail later.

[0063] After the width direction stretching step is completed, the biaxially stretched film is heat-treated at a specific temperature to obtain a biaxially oriented film. In the heat treatment step, the film may be relaxed in the width direction.

[0064] The biaxially oriented polypropylene film for transfer substrate thus obtained may be subjected to a corona discharge treatment on at least one side, if necessary, and then wound up on a winder to obtain a film roll.

[0065] Each step will be described in detail below. (Extrusion Step) First, a polypropylene resin composition containing a polypropylene resin as a main component is heated and melted in a range of 200°C to 300°C using a single-screw or twin-screw extruder, and the sheet-shaped molten polypropylene resin composition is extruded from a T-die and brought into contact with a metal cooling roll for cooling and solidification. The resulting unstretched sheet is preferably then placed in a water bath. The temperature of the cooling roll, or the cooling roll and water bath, is preferably in the range of 10°C to Tc. If increased transparency of the film is desired, cooling and solidification using a cooling roll at a temperature in the range of 10 to 50°C is preferred. A cooling temperature of 50°C or less tends to increase the transparency of the unstretched sheet, and is more preferably 40°C or less, and even more preferably 30°C or less. In order to increase the degree of crystalline orientation after sequential biaxial stretching, it may be preferable to set the cooling temperature to 40°C or higher. However, when using a propylene homopolymer with a mesopentate fraction of 97.5% or higher as described above, a cooling temperature of 40°C or lower is more preferable in order to facilitate the subsequent stretching step and reduce thickness unevenness, and a temperature of 30°C or lower is even more preferable. The thickness of the unstretched sheet is preferably 3500 μm or lower in terms of cooling efficiency, and more preferably 3000 μm or lower, and can be appropriately adjusted depending on the film thickness 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.

[0066] (Longitudinal Stretching Step) The lower limit of the longitudinal stretching ratio is preferably 3.5 times, more preferably 3.8 times, and particularly preferably 4.2 times. Within this range, strength is easily increased and thickness unevenness is reduced. The upper limit of the longitudinal stretching ratio is preferably 7.0 times, more preferably 6.0 times, and particularly preferably 5.0 times. Within this range, width direction stretching in the width direction stretching step is easy, improving productivity. The lower limit of the longitudinal stretching temperature is preferably Tm - 30°C, more preferably Tm - 27°C, and even more preferably Tm - 25°C. Within this range, subsequent width direction stretching is easy and thickness unevenness is reduced. The upper limit of the longitudinal stretching temperature is preferably Tm - 7°C, more preferably Tm - 10°C, and even more preferably Tm - 12°C. Within the above range, the heat shrinkage rate is easily reduced, and there is little deterioration in quality due to difficulty in applying stretching to the stretching rolls or increased surface roughness. The longitudinal stretching may be carried out in two or more stages using three or more pairs of stretching rolls.

[0067] (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.

[0068] (Transverse Stretching Step) In the width direction stretching step after the preheating step, a preferred method is as follows.

[0069] In the width direction stretching step, stretching is preferably performed at a temperature of Tm - 10°C or higher and the preheating temperature or lower. The lower limit of the temperature in the width direction stretching step is more preferably Tm - 9°C, even more preferably Tm - 7°C, and particularly preferably Tm - 5°C. When the width direction stretching temperature is within this range, the rigidity of the obtained biaxially oriented film is likely to be improved. The upper limit of the temperature in the width direction stretching step is preferably Tm + 10°C, even more preferably Tm + 7°C, and particularly preferably Tm + 5°C. When the width direction stretching temperature is within this range, stretching unevenness is less likely to occur.

[0070] In the width direction stretching step, a later stretching step in which stretching is performed at a lower temperature may be added following width direction stretching within the above temperature range. That is, a section (early section) in which stretching is performed at a temperature of Tm-10°C or higher and Tm+10°C or lower may be followed by a section (late section) in which stretching is performed at a temperature lower than the temperature in the early section and at Tm-70°C or higher and Tm-5°C or lower. Providing an early section and a late section makes it easier to increase rigidity. The lower limit of the stretching temperature in the late section is preferably Tm-65°C, more preferably Tm-60°C, and even more preferably Tm-55°C. When the stretching temperature in the late section is within this range, film formation is likely to be stable.

[0071] The final width direction stretching ratio in the width direction stretching step is preferably 10 times or more, more preferably 11 times or more, and even more preferably 11.5 times or more. A stretching ratio of 10 times or more tends to increase the rigidity of the film and reduce thickness unevenness. The upper limit of the width direction stretching ratio is preferably 20 times, more preferably 17 times, and even more preferably 15 times. A stretching ratio of 20 times or less tends to reduce the heat shrinkage rate and makes the film less likely to break during stretching. When a later section is added and / or when width direction re-stretching, as described below, is performed, it is preferable that the total stretching ratio be within the above range. In this case, the lower limit of the stretching ratio in the earlier stretching step is preferably 4 times, more preferably 5 times, even more preferably 6 times, and particularly preferably 6.5 times. The upper limit of the stretching ratio at the end of the earlier section is preferably 15 times, more preferably 14 times, and even more preferably 13 times.

[0072] It is preferable to cool the film immediately after the end of width direction stretching, i.e., when the final width direction stretch ratio is reached. The cooling temperature at this time is preferably equal to or lower than the width direction stretching temperature and is preferably at least Tm-80°C and not more than Tm-15°C, more preferably at least Tm-80°C and not more than Tm-20°C, even more preferably at least Tm-80°C and not more than Tm-30°C, and particularly preferably at least Tm-70°C and not more than Tm-40°C. By adding a cooling step, crystallization occurs, the crystalline orientation is fixed, and the orientation history is maintained even when the temperature is subsequently raised to a temperature above the melting point, resulting in increased crystalline orientation in the film. The temperature at the end of width direction stretching to the cooling temperature can be gradually reduced, but it can also be reduced in steps or in a single step. Reducing the temperature in steps or in a single step is preferable because it is easier to increase the crystalline orientation in the film.

[0073] After cooling the film, it is preferable to stretch it again in the width direction at a high temperature (hereinafter also referred to as width direction re-stretching). When the film is cooled and then stretched again in the width direction at a high temperature, the crystalline orientation of the film is easily increased, and therefore rigidity is easily increased. The lower limit of the stretching temperature when stretching again in the width direction is preferably Tm - 5 ° C, more preferably Tm ° C, even more preferably Tm + 5 ° C, still more preferably Tm + 7 ° C, and particularly preferably Tm + 9 ° C. When the temperature is Tm - 5 ° C or higher, rigidity is easily increased and the heat shrinkage rate is easily reduced. The upper limit of the width direction re-stretching temperature is preferably Tm + 20 ° C, more preferably Tm + 18 ° C, and even more preferably Tm + 16 ° C. When the temperature is Tm + 20 ° C or lower, rigidity is easily increased.

[0074] The lower limit of the width direction re-stretching ratio at high temperature is preferably 1.05 times, more preferably 1.1 times, and even more preferably 1.15 times. The upper limit of the width direction re-stretching ratio at high temperature is preferably 2 times, more preferably 1.7 times, and even more preferably 1.5 times. If the re-stretching ratio is too high, the heat shrinkage may become too large, thickness unevenness may occur, or the film may break.

[0075] In other words, instead of immediately relaxing the film at a high temperature after widthwise stretching as in the conventional method, it has been found that by stretching the film again in the widthwise direction at a temperature sufficiently higher than the melting point, it is possible to further improve the rigidity while reducing the heat shrinkage. That is, in the step after the first widthwise stretching, it is preferable to perform stretching at Tm + 5°C or higher. At Tm + 5°C or higher, the mobility of the molecular chains is sufficiently high, and stretching makes it easier to eliminate the effects of molecular chain entanglement. As a result, the molecular chains are less likely to be restrained, making it less likely for disordered molecular orientation to occur and allowing sufficient crystallization to proceed. By cooling the film below a temperature at which crystallization is possible after widthwise stretching at a high temperature, the crystalline orientation is fixed, and a high-melting-point film with a high degree of crystallization and thick crystalline lamellae can be obtained.

[0076] Furthermore, even in areas other than the crystalline lamellae, there are fewer molecular chains with large distortions in molecular orientation constrained by entanglement points, so the film is less likely to shrink even when the crystals begin to melt. Furthermore, as the degree of crystallization improves and the crystalline lamellae become thicker, the melting point tends to increase, making it difficult for melting to occur below the melting point. This makes it easier to reduce the heat shrinkage rate. As a result, it has become possible to further improve rigidity while reducing the heat shrinkage rate.

[0077] In the conventional film-making process (extrusion - longitudinal stretching - width stretching - heat treatment), to eliminate distortion caused by width stretching at temperatures lower than the melting point, the film is exposed to a high temperature above the melting point during the heat treatment process, and relaxation of several to several tens of percent is performed to reduce the heat shrinkage. Relaxation eliminates the difficulty of crystallization due to molecular chain restraint, contributing to a reduction in the heat shrinkage. However, conversely, the reduction in width-direction orientation of molecular chains generated during the width-direction stretching process also reduces rigidity, making it difficult to achieve both low heat shrinkage and high rigidity. Furthermore, excessively high temperatures can cause film whitening. In the conventional film-making process (extrusion - longitudinal stretching - width stretching - heat treatment), increasing the temperature during the width-direction stretching step increases molecular chain mobility, and stretching without residual distortion promotes melting of the crystals generated by the longitudinal stretching, resulting in a decrease in crystalline orientation. In the method of the embodiment, the film is stretched once in the width direction, and after being sufficiently oriented in the width direction, the film has sufficient tension even when the fixed crystalline orientation is melted by cooling, and is then stretched again at a high temperature of Tm + 5°C or higher. Therefore, even when stretched again, there is sufficient tension, and there is little concern about thickness unevenness or film breakage. The stretching ratio at high temperatures should be sufficient to disentangle and align the molecular chains, and should be 1.05 times or more. A stretching ratio of 2 times or less is less likely to cause thickness unevenness.

[0078] In this way, by using a highly crystalline polypropylene resin with high stereoregularity and a high melting point and employing the above-mentioned longitudinal stretching process, widthwise stretching process, cooling process, and high-temperature stretching process, the molecules of the polypropylene resin are aligned to a significantly high degree in the main orientation direction (which corresponds to the width direction in the above-mentioned widthwise stretching process), and therefore, the resulting biaxially oriented film is more likely to have a strong crystalline orientation and produce a larger number of crystals with a high melting point.

[0079] Furthermore, by increasing the low-molecular-weight component of the polypropylene resin, the entanglement of molecular chains is reduced, which makes it easier to increase the crystallinity of the film and reduce the areas other than the crystalline lamellae. Furthermore, by weakening the heat shrinkage stress in the areas other than the crystalline lamellae, it is easier to further reduce the heat shrinkage rate. With conventional technology, it has been difficult to simultaneously strengthen the crystalline orientation and reduce the amorphous components not bound by the crystals. In other words, if either rigidity or heat shrinkage rate is improved, the other property tends to deteriorate. Considering these factors, the effect of achieving both of these properties can be said to be a groundbreaking one.

[0080] (Heat Treatment Step) If necessary, the biaxially stretched film can be heat-treated to further reduce the heat shrinkage. The upper limit of the heat treatment temperature is preferably the high-temperature re-stretching temperature described above, more preferably the high-temperature re-stretching temperature -2°C, and even more preferably the high-temperature re-stretching temperature -3°C. By setting the temperature at or below the high-temperature re-stretching temperature, the rigidity is less likely to decrease, the film surface roughness does not become too large, and the film is less likely to whiten. The lower limit of the heat treatment temperature is preferably Tm -3°C, more preferably Tm -2°C, and particularly preferably Tm°C. For the purpose of adjusting the heat shrinkage, the film may be relaxed (relaxed) in the width direction during heat treatment, and the upper limit of the relaxation rate is preferably 5%, more preferably 3%, and even more preferably 1%. Within the above range, the rigidity is less likely to decrease and the film thickness variation is likely to be small. When the rigidity is to be further increased, heat treatment may not be performed.

[0081] (Cooling step) After stretching in the width direction, it is preferable to cool the film immediately after stretching again in the width direction at Tm-5°C or higher, or immediately after the heat treatment step. The cooling temperature at this time is preferably 10°C or higher and 140°C or lower, more preferably 20°C or higher and 120°C or lower, even more preferably 80°C or lower, and particularly preferably 50°C or lower. By providing a cooling step, the state of the film can be fixed. The biaxially oriented polypropylene film thus obtained is preferably subjected to corona discharge, plasma treatment, flame treatment, etc., as necessary.

[0082] (Release layer-laminated polypropylene film for transfer) The biaxially oriented polypropylene film for transfer substrate described above may be used as a transfer film without any particular release treatment, and the release properties may be adjusted by corona treatment, flame treatment, plasma treatment, etc. Also, the release properties may be adjusted in a gas atmosphere containing a fluorine-based compound or a silicone-based compound. Below, a release layer-laminated polypropylene film for transfer according to an embodiment will be described. The release layer-laminated polypropylene film for transfer has any of the biaxially oriented polypropylene films for transfer substrate described above and a release layer laminated on at least one surface of the biaxially oriented polypropylene film for transfer substrate.

[0083] When preparing a release layer-laminated polypropylene film for transfer, a release agent may be applied to the surface of the biaxially oriented polypropylene film for transfer substrate. When a release agent is applied to the surface, it is preferable that the wet tension of the surface of the biaxially oriented polypropylene film for transfer substrate is 38 mN / m or more. A wet tension of 38 mN / m or more improves adhesion to the release layer. To achieve a wet tension of 38 mN / m or more, physicochemical surface treatments such as corona treatment, flame treatment, and plasma treatment are preferably performed. For example, in corona treatment, it is preferable to use a preheated roll and a treatment roll and discharge in the air. The wet tension is preferably 44 mN / m or less, more preferably 43 mN / m or less, and even more preferably 42 mN / m or less. Note that the wet tension may be less than 38 mN / m when no release agent is applied, and can be adjusted by the surface treatment conditions to achieve the required releasability, and surface treatment may not be necessary.

[0084] The release agent may contain silicone resin, fluororesin, alkyd resin, amino resin, various waxes, aliphatic olefin, long-chain alkyl group-containing resin, etc., and each resin may be used alone or in combination of two or more kinds.

[0085] The silicone resin used as the release agent can be any silicone resin commonly used in release agents, and can be selected from silicone resins commonly used in the relevant field, such as those described in "Silicone Materials Handbook" (edited by Toray Dow Corning, August 1993). Generally, heat-curable or ionizing radiation-curable silicone resins (which encompass both resins and resin compositions) are used. Examples of heat-curable silicone resins include condensation reaction and addition reaction silicone resins, and examples of ionizing radiation-curable silicone resins include ultraviolet or electron beam-curable silicone resins. These are applied to a film substrate and then dried or cured to form a release layer.

[0086] The curable silicone resin preferably has a degree of polymerization after curing of about 500,000 to 200,000, particularly about 1,000 to 100,000. Specific examples of such resins include the following: KS-718, KS-774, KS-775, KS-778, KS-779H, KS-830, KS-835, KS-837, KS-838, KS-839, KS-841, KS-843, and KS-848 manufactured by Shin-Etsu Chemical Co., Ltd. -847, KS-847H, X-62-2418, X-62-2422, X-62-2125, 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; manufactured by Toshiba Silicone Co., Ltd. TPR-6701, TPR-6702, TPR-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-Q3-3 manufactured by Dow Corning Corporation; 003, 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 Toray Dow Corning Silicone Co., Ltd.; SILCOLEASE 425 manufactured by ICI Japan Co., Ltd. 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.

[0087] Examples of the silicone resin of the addition reaction system include a resin that is cured by reacting a polydimethylsiloxane having vinyl groups introduced at the terminal or side chain with a hydrogen siloxane using a platinum catalyst. 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 Toray Dow Corning Co., Ltd., 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.

[0088] An example of the condensation reaction 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.

[0089] Examples of the above-mentioned UV-curable or electron beam-curable silicone resins include, for example, the most basic types, resins that crosslink and harden by a radical reaction similar to normal silicone rubber crosslinking, resins that photocure by the introduction of acrylic groups, resin compositions in which UV decomposes an onium salt to generate a strong acid that cleaves the epoxy ring and crosslinks, 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.

[0090] Amino resins are resins obtained by the addition-condensation reaction of aldehydes with compounds containing amino groups, such as urea, melamine, guanamine, and aniline. Examples include aniline aldehyde resins, urea resins, melamine resins, benzoguanamine resins, and acetoguanamine resins. The amino resins may be modified with long-chain alkyl groups, which are described below.

[0091] 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 and the like may be added as needed.

[0092] 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.

[0093] 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 obtained by Diels-Alder reaction such as cyclopentadiene-maleic anhydride adduct, terpene-maleic anhydride adduct, and rosin-maleic anhydride adduct.

[0094] Examples of various waxes include paraffin wax, microcrystalline wax, palm wax, carnauba wax, candelilla wax, rice wax, soy wax, wax, beeswax, and lanolin wax.

[0095] Examples of the aliphatic olefin include polyethylene-based, polypropylene-based, and polymethylpentene-based resins.

[0096] 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.

[0097] The long-chain alkyl group preferably has 6 to 32 carbon atoms, more preferably 8 to 26 carbon atoms, and even more preferably 10 to 22 carbon atoms. 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.

[0098] These release agents containing long-chain alkyl group-containing resins are commercially available, for example, as 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.

[0099] 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.

[0100] The resin of the release 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 layer, and the precursor may be subjected to a crosslinking reaction using ultraviolet light, an electron beam, or the like.

[0101] When a release agent is used, it may be used alone or in combination of two or more. To adjust the release force, it is also possible to add an additive such as a light release additive or a heavy release additive. The resulting biaxially oriented polypropylene film having a release layer has particularly excellent releasability.

[0102] The release layer may contain particles with a particle size of 1 μm or less, but preferably does not substantially contain particles or other protrusion-forming materials in terms of pinhole formation. Additives such as adhesion improvers and antistatic agents may be added to the release layer. In addition, in order to improve adhesion to 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 layer.

[0103] The thickness of the release 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 release layer thickness of 0.005 μm or more is preferable because release performance is maintained. Furthermore, a release layer 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. Another layer may be provided between the biaxially oriented polypropylene film and the release layer.

[0104] The method for forming the release layer is not particularly limited. A coating solution containing a release resin dissolved or dispersed therein is applied to one side of a biaxially oriented polypropylene film by coating or the like, and the solution is then dried to remove the solvent, followed by heat drying, heat curing, or UV curing. The drying temperature during solvent drying and heat curing is preferably 100 to 170°C. A drying temperature higher than 170°C may cause the film to wrinkle due to heat. On the other hand, a low drying temperature may result in insufficient heat curing of the release layer, resulting in insufficient release properties. Generally, biaxially oriented polypropylene films have lower thermal dimensional stability at high temperatures than biaxially oriented polyester films, and therefore tend to wrinkle or deteriorate flatness due to heat during drying of the release layer. However, the biaxially oriented polypropylene film for transfer substrates of the present embodiment can suppress the occurrence of wrinkles. The heat drying time is typically 10 to 60 seconds.

[0105] As a method for applying the coating liquid, any known coating method can be applied, and conventionally known methods such as roll coating methods such as gravure coating and reverse coating, bar coating methods such as wire bar coating, die coating, spray coating, and air knife coating can be used.

[0106] The release layer may be an underlayer of the transfer layer described later, or may be a release layer for preventing the transfer layer from sticking to the surface of the biaxially oriented polypropylene film for transfer substrate opposite the transfer layer when the laminate of the biaxially oriented polypropylene film for transfer substrate and the transfer layer is wound into a roll. Also, the release layer may be laminated on both sides of the biaxially oriented polypropylene film.

[0107] The following describes a transfer laminate film according to an embodiment. The transfer laminate film includes a biaxially oriented polypropylene film for transfer substrates and a transfer layer. Next, the transfer layer and the transfer target will be described. Examples of transfer layers include printed layers such as patterns and characters; decorative metal thin films; thermal transfer ink layers; photosensitive resin layers; optical functional layers such as retardation layers, polarizing layers, circularly polarized reflective layers, hard coat layers, anti-reflection layers, and low-reflection layers; conductive layers; circuits; adhesive layers; pressure-sensitive adhesive layers; and rubber sheet layers. The transfer layer preferably includes at least one layer selected from these. These layers require high temperatures or high precision when providing a transfer layer or during transfer. The biaxially oriented polypropylene film for transfer substrates according to an embodiment has excellent heat resistance, and even under conditions exceeding 130°C during processing such as coating and drying, the film shrinks only slightly. It can be used at temperatures exceeding 150°C for short periods of time, and furthermore has excellent rigidity. Therefore, the above-mentioned transfer layer and biaxially oriented polypropylene film for transfer substrates are a suitable combination. Furthermore, when peeling off the substrate film, the excellent rigidity allows for smooth peeling, which also allows for high-speed transfer and improves productivity.

[0108] 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 substrate film. 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 substrate film, or a protective layer may be provided on the substrate 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, resin molded products, conductive thin film laminates, and the like, and composites thereof may also be used. Wood, glass, ceramics, metal, and resin molded products 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 film is placed on the transfer target, and the transfer is performed using a heated roll or a heated mold. Using a biaxially oriented polypropylene film for the transfer substrate reduces dimensional change and deterioration of flatness even when dried at a higher temperature when providing the printing layer, thereby increasing productivity. Furthermore, transfer printing can be performed at higher speeds, making it easier to perform highly accurate transfer printing without misalignment.

[0109] Decorative metal thin films are transferred to 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. The decorative metal thin film can be formed by laminating a metal foil, or by methods such as vapor deposition and sputtering. The decorative metal thin film may be directly in contact with the substrate film, via an adhesive layer in the case of a metal foil, or may be formed on a protective layer provided on the substrate 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 the metal thin film may be an uncolored metal such as aluminum, so that the appearance after transfer is gold or copper. A printed layer may also be provided between the decorative metal thin film and the substrate film. Examples of the target object for transfer include those similar to the printed layer. By using biaxially oriented polypropylene film for transfer substrates, dimensional changes and deterioration of flatness due to temperature during vapor deposition, etc. are reduced, transfer can be performed at higher speeds, and even patterns with fine design details can be transferred with high precision without misalignment.

[0110] 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 a biaxially oriented polypropylene film for the transfer substrate, the temperature of the heating head can be increased, making it easier to print at higher speeds.

[0111] The photosensitive resin layer can be a resist layer and may be negative or positive. It can be transferred to a transfer target having a conductive layer, such as a thin film of copper or an ITO layer, on its surface, and used to form a pattern on the conductive layer. In pattern formation, radiation exposure may be performed before or after the substrate film is peeled off. Examples of transfer targets having a conductive layer include films, glass plates, ceramic plates, and resin plates, each of which has a conductive layer formed on its surface. The resin plate may be a composite plate containing paper, glass fiber, or the like. By using a biaxially oriented polypropylene film for transfer substrates, dimensional changes and deterioration of flatness due to heat during application of the photosensitive resin layer or heat during exposure are reduced, making it easier to form finer patterns.

[0112] 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 alignment 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 alignment. The alignment of the liquid crystal compound can be achieved by rubbing the surface of the substrate 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 alignment control layer as a lower layer of the retardation layer and rubbing the alignment control layer or by irradiating it with polarized light to impart an alignment control function. This alignment control is also considered part of the retardation layer. The retardation layer may be a multi-layer structure. The retardation layer may be provided directly in contact with the substrate film, or may be provided on a protective layer provided on the substrate film.

[0113] 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.

[0114] The circularly polarized reflective layer reflects optical rotation in one direction and transmits optical rotation in multiple directions. Cholesteric liquid crystals are preferably used. 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 the substrate film, or may be provided on a protective layer provided on the substrate film. Examples of materials to which the retardation layer, polarizing layer, and circularly polarized reflective layer are transferred include films, glass plates, and resin plates. The transfer target is preferably transparent, but may also be specularly reflective depending on the application. To align these liquid crystal compounds, they are often heated to 110 to 140°C. However, by using a biaxially oriented polypropylene film for transfer substrate, dimensional changes and deterioration of flatness due to heat during alignment and fixation of the liquid crystal compound are minimized, allowing the liquid crystal to be oriented as designed, resulting in a higher-quality, more uniform retardation layer, polarizing layer, and circularly polarized reflective layer.

[0115] The hard coat layer prevents dents and scratches on the surface of the transfer target. A 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. An anti-reflection layer is provided on the surface of the transfer target with a layer having a different refractive index, suppressing reflection by interference of reflected light at multiple interfaces. Examples of transfer targets include films, glass plates, resin plates, and resin molded products. The transfer target is preferably transparent, and a preferred example is one 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 a biaxially oriented polypropylene film for transfer substrates allows for high dimensional stability and maintains 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, thereby enabling high-speed processing. Curable adhesives are also used during transfer, which similarly facilitates high-speed transfer.

[0116] 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. The use of a biaxially oriented polypropylene film for transfer substrates allows for high dimensional stability and flatness to be maintained even when subjected to high temperatures during vapor deposition, sputtering, CVD, and other processes, resulting in a high-quality conductive film.

[0117] 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 the substrate film, or may be provided on a protective layer provided on the substrate film. The circuit may be processed into a circuit after providing the conductive layer as described above, or may be printed as a circuit using a conductive polymer or conductive paste. Examples of objects to be transferred include films, glass plates, ceramic plates, and resin plates, and the resin plate may be a composite plate containing paper, glass fiber, or the like. By using a biaxially oriented polypropylene film for transfer substrate, it is possible to form a more precise circuit.

[0118] The adhesive layer is a layer containing an adhesive. Suitable adhesives include hot-melt adhesives. 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 a substrate 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.

[0119] The reactive adhesive may be reacted by heat or radiation after the substrate film of the adhesive layer is peeled off after transfer and the object to be adhered is placed on the surface, or the adhesive reaction may be initiated by irradiation with radiation before peeling off the substrate film or by heat during transfer, and then the substrate film is peeled off and the object to be adhered is placed on top. In the case of a moisture-curing adhesive, the reaction is initiated when the adhesive layer absorbs moisture after peeling off the release film or substrate film provided on the opposite side of the adhesive layer. The hot melt adhesive may also have the above-mentioned reactivity. 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.

[0120] Many of these adhesives require high temperatures when applied to the transfer substrate film or during transfer, and using a biaxially oriented polypropylene film for transfer substrates makes it easier to process and transfer at higher temperatures. In addition, when the transfer layer is affected by oxygen or humidity, such as in the case of reactive adhesives, a barrier layer may be provided on the biaxially oriented polypropylene film for transfer substrates. Examples of barrier layers include vapor-deposited layers of aluminum, silicon oxide, aluminum oxide, etc., and barrier coat layers of inorganic layered compounds or polyvinylidene chloride, etc.

[0121] The pressure-sensitive adhesive layer is a layer containing a pressure-sensitive adhesive. Examples of the pressure-sensitive adhesive include acrylic and rubber-based pressure-sensitive adhesives, and a suitable example is an acrylic optical pressure-sensitive adhesive. A hot-melt pressure-sensitive adhesive may also be used. When providing a pressure-sensitive adhesive layer on a transfer substrate film, high temperatures are required during coating, and a crosslinking reaction due to radiation or heat is required after coating. However, by using a biaxially oriented polypropylene film for transfer substrates, higher temperatures can be achieved, thereby increasing productivity.

[0122] 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.

[0123] 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.

[0124] As described above, the transfer target is preferably paper, film, cloth, wood, glass, ceramics, metal, resin molded body, or conductive thin film laminate. Furthermore, as described above, the biaxially oriented polypropylene film for transfer substrates according to the embodiment is resistant to wrinkling, dimensional changes, and deterioration of flatness during the formation of a transfer layer or during processing, thereby improving the appearance quality of the transfer laminate film and enabling it to be used as a transfer film for high-resolution transfer applications. Furthermore, even at high temperatures during transfer, it is resistant to wrinkling and dimensional changes, improving the appearance quality and enabling highly accurate transfer. In order to utilize its excellent properties, biaxially oriented polypropylene films for thin film production are preferably used in cases where the process of forming a transfer layer or the process of processing includes a high-temperature environment. Specific processes include a drying process, a crosslinking reaction process, a phase conversion process, a phase separation process, and a surface planarization process. Specific temperatures preferably include a process in an environment of 110°C or higher, more preferably 115°C or higher, even more preferably 120°C or higher, and particularly preferably 125°C or higher. The upper limit of the environmental temperature is preferably 160°C, more preferably 155°C, and even more preferably 150°C. The lower limit of the time for the step of reaching the above temperature is preferably 2 seconds, more preferably 5 seconds, and even more preferably 10 seconds. The upper limit of the time is preferably 60 minutes, more preferably 45 minutes, and even more preferably 30 minutes. However, when the temperature exceeds 155°C, it is preferable to avoid a time of more than 30 seconds, more preferably to avoid a time of more than 20 seconds, and even more preferably to avoid a time of more than 15 seconds. When the temperature exceeds 150°C, it is preferable to avoid a time of more than 90 seconds, more preferably to avoid a time of more than 60 seconds, and even more preferably to avoid a time of more than 45 seconds. When the temperature exceeds 140°C, it is preferable to avoid a time of more than 3 minutes, more preferably to avoid a time of more than 2 minutes, and even more preferably to avoid a time of more than 1 minute. When the temperature exceeds 130°C, it is preferable to avoid a time of more than 5 minutes, more preferably to avoid a time of more than 4 minutes, and even more preferably to avoid a time of more than 3 minutes.

[0125] When the transfer layer is provided on the film by melting using a melt extrusion method or the like, the temperature of the molten transfer layer is preferably 180°C or less, more preferably 170°C or less, even more preferably 160°C or less, particularly preferably 150°C or less, and most preferably 145°C or less. However, if the temperature exceeds 150°C, it is preferable to pass the 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, more preferably 125°C or more, and even more preferably 130°C or more.

[0126] When contacting with a heating body such as a heat roll, the temperature of the heating body is preferably 120°C or higher, more preferably 125°C or higher, and even more preferably 130°C or higher. The temperature of the heating body is preferably 160°C or lower, more preferably 155°C or lower, and even more preferably 150°C or lower. The contact time with the heating body is preferably 0.5 seconds or higher, more preferably 1 second or higher, even more preferably 1.5 seconds or higher, and particularly preferably 2 seconds or higher. The contact time is preferably 180 seconds or lower, more preferably 120 seconds or lower, even more preferably 90 seconds or lower, and particularly preferably 60 seconds or lower. However, if the temperature of the heating body exceeds 155°C, it is preferable to avoid a time of 90 seconds or higher, and if it exceeds 150°C, it is preferable to avoid a time of 60 seconds or higher.

[0127] In the deposition, sputtering, CVD, etc., it is preferable to perform the process while cooling so that the film temperature does not exceed 150°C.

[0128] When the transfer process is a heat transfer process in which 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, it is also preferable to use a biaxially oriented polypropylene film for a transfer substrate.

[0129] The transfer laminate film 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.

[0130] The transfer method of the embodiment will be described below. The transfer method of the embodiment includes a step of bonding a transfer laminate film to a transfer object, and a step of peeling a biaxially oriented polypropylene film for transfer substrate of the transfer laminate film from the transfer object to which the transfer laminate film is bonded. In the bonding step, as described above, the transfer laminate film can be overlaid on the transfer object and bonded using a heated roll or a heated mold. In the peeling step, it is sufficient to peel at least the biaxially oriented polypropylene film for transfer substrate from the transfer object, and if the transfer laminate film has a release layer, it is preferable to peel the biaxially oriented polypropylene film for transfer substrate and the release layer from the transfer object.

[0131] (Second Disclosure) A biaxially oriented polypropylene film for thin film manufacturing processes according to an embodiment of the second disclosure will be described below. The biaxially oriented polypropylene film for thin film manufacturing processes according to the embodiment satisfies the following (1), (2), and (3): (1) The mesopentad fraction of the polypropylene resin constituting the biaxially oriented polypropylene film for thin film manufacturing processes is 97.5% or more. (2) The relationship between the loop stiffness stress S [mN] in the width direction and the thickness t (μm) satisfies the following formula (A): S≧0.0010×t ３ ...(A) (3) When separated into a crystalline component (I), a constrained amorphous component (II), and an unconstrained amorphous component (III) as determined by pulsed NMR using the solid echo method, the ratio of (III) is 7% or less.

[0132] The biaxially oriented polypropylene film for thin film manufacturing processes according to the embodiment is preferably made of a polypropylene resin composition containing a polypropylene resin as a main component. The term "main component" refers to a polypropylene resin content of 90% by mass or more in the polypropylene resin composition, more preferably 93% by mass or more, even more preferably 95% by mass or more, and particularly preferably 97% by mass or more. This content may be 100% by mass or less, or even 99% by mass or less. The polypropylene resin composition may contain additives. The additives may include a crystal nucleating agent, an antioxidant, a heat stabilizer, a slip agent, an antistatic agent, an antiblocking agent, a filler, a viscosity modifier, a color inhibitor, or a combination thereof.

[0133] (Polypropylene Resin) The polypropylene resin may contain a polypropylene homopolymer, a copolymer of propylene and ethylene and / or an α-olefin having 4 or more carbon atoms, or a mixture thereof. Of these, a propylene homopolymer that is substantially free of ethylene and / or an α-olefin having 4 or more carbon atoms is preferred. In the case of a copolymer, the amount of ethylene and / or an α-olefin 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, and particularly preferably 0.1 mol% or less, based on 100 mol% of all structural units of the copolymer. Within the above range, crystallinity is likely to be improved. The amount of this component may be 0.01 mol% or more. Examples of the α-olefin component having 4 or more carbon atoms that constitutes such a copolymer include 1-butene, 1-pentene, 3-methylpentene-1, 3-methylbutene-1, 1-hexene, 4-methylpentene-1, 5-ethylhexene-1, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-eicosene, etc. The polypropylene resin may contain two or more different polypropylene homopolymers, copolymers with ethylene and / or α-olefins having 4 or more carbon atoms, or mixtures thereof.

[0134] (Stereoregularity) The mesopentad fraction (hereinafter sometimes abbreviated as [mmmm]%) of the polypropylene resin is 13 It is quantified based on the peak assignments in a C-NMR spectrum and refers to the proportion of five consecutive propylene monomer units in a polypropylene resin having the same stereostructure, and is an index of stereoregularity. The mesopentad fraction of a polypropylene resin is 97.5% or more, preferably in the range of 97.5 to 99.9%, more preferably in the range of 98.0 to 99.7%, even more preferably in the range of 98.3 to 99.5%, and particularly preferably in the range of 98.5 to 99.3%. A mesopentad fraction of 97.5% or more enhances the crystallinity of the polypropylene resin, improving the melting point, crystallinity, and crystalline orientation of the crystals in the film, and making it easier to achieve rigidity and heat resistance at high temperatures. A mesopentad fraction of 99.9% or less facilitates cost reduction in polypropylene production and reduces breakage during film formation. The mesopentad fraction is measured by nuclear magnetic resonance (NMR). A mesopentad fraction of 99.5% or less is even more preferable. In order to set the mesopentad fraction of the polypropylene resin within the above range, a method of washing the obtained polypropylene resin powder with a solvent such as n-heptane, a method of appropriately selecting a catalyst and / or co-catalyst, and a method of appropriately selecting the components of the polypropylene resin composition are preferably employed.

[0135] (Melting temperature) The melting temperature (Tm) of the polypropylene resin constituting the biaxially oriented polypropylene film for thin film production process, measured by DSC, i.e., the lower limit of the melting point, is preferably 160 ° C, more preferably 161 ° C, even more preferably 162 ° C, even more preferably 163 ° C, and particularly preferably 164 ° C. When Tm is 160 ° C or higher, rigidity and heat resistance at high temperatures are easily obtained. The upper limit of Tm is preferably 170 ° C, more preferably 169 ° C, even more preferably 168 ° C, even more preferably 167 ° C, and particularly preferably 166 ° C. When Tm 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. The melting temperature can also be further increased by blending a crystal nucleating agent with the polypropylene resin. Tm is the main endothermic peak temperature associated with melting, which is observed when 1 to 10 mg of a sample is packed into an aluminum pan and set in a differential scanning calorimeter (DSC), melted at 230°C for 5 minutes in a nitrogen atmosphere, cooled to 30°C at a scanning rate of -10°C / min, held for 5 minutes, and then heated again at a scanning rate of 10°C / min.

[0136] (Crystallization temperature) The lower limit of the crystallization temperature (Tc) of the polypropylene resin constituting the biaxially oriented polypropylene film for thin film production process, as measured by DSC, is preferably 105 ° C, more preferably 108 ° C, and even more preferably 110 ° C. If Tc is 105 ° C or higher, crystallization is likely to proceed during width direction stretching and the subsequent cooling process, making it easier to obtain rigidity and heat resistance at high temperatures. The upper limit of Tc is preferably 135 ° C, more preferably 133 ° C, even more preferably 132 ° C, even more preferably 130 ° C, particularly preferably 128 ° C, and most preferably 127 ° C. If Tc is 135 ° C or lower, it is difficult to increase the cost of polypropylene production and the film is less likely to break during film formation. The crystallization temperature can also be further increased by blending a crystal nucleating agent with the polypropylene resin. Tc is the main peak temperature of the exothermic peak observed when 1 to 10 mg of a sample is packed into an aluminum pan, set in a DSC, melted at 230°C for 5 minutes in a nitrogen atmosphere, and cooled to 30°C at a scanning rate of -10°C / min.

[0137] (Melt Flow Rate) The melt flow rate (MFR) of the polypropylene resin constituting the biaxially oriented polypropylene film for thin film manufacturing processes, as 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, particularly preferably 5.0 to 20 g / 10 min, and most preferably 6.0 to 18 g / 10 min. When the polypropylene resin has a melt flow rate (MFR) of 4.0 g / 10 min or more, a biaxially oriented polypropylene film for thin film manufacturing processes with low thermal shrinkage is easily obtained. Furthermore, when the polypropylene resin has a melt flow rate (MFR) of 30 g / 10 min or less, the film formability of the film is easily maintained.

[0138] From the viewpoint of film properties, the lower limit of the melt flow rate (MFR) (230°C, 2.16 kgf) of the polypropylene resin constituting the film is preferably 5.0 g / 10 min, 5.5 g / 10 min, 6.0 g / 10 min, 6.3 g / 10 min, 6.5 g / 10 min, 6.8 g / 10 min, and 7.0 g / 10 min, in that order. When the melt flow rate (MFR) of the polypropylene resin is 5.0 g / 10 min or higher, the amount of low molecular weight components in the polypropylene resin constituting the film increases. If a polypropylene resin containing a large amount of such low molecular weight components is used and a width direction stretching step in the film formation process described below is adopted, the oriented crystallization of the polypropylene resin is further promoted, the crystallinity of the film is more likely to be increased, and in addition, the entanglement of polypropylene molecular chains in the amorphous portion is reduced, which makes it easier to improve heat resistance. In order to set the melt flow rate (MFR) of the polypropylene resin within the above range, it is preferable to employ a method for controlling the average molecular weight or molecular weight distribution of the polypropylene resin.

[0139] That is, the lower limit of the amount of components having a molecular weight of 100,000 or less in the GPC cumulative curve of the polypropylene resin constituting the biaxially oriented polypropylene film for thin film production processes is preferably 35% by mass, more preferably 38% by mass, even more preferably 40% by mass, even more preferably 41% by mass, and particularly preferably 42% by mass. The upper limit of the amount of components having a molecular weight of 100,000 or less in the GPC cumulative curve is preferably 65% ​​by mass, more preferably 60% by mass, and even more preferably 58% by mass. When the amount of components having a molecular weight of 100,000 or less in the GPC cumulative curve is 65% by mass or less, the film strength is less likely to decrease. In this case, if the polypropylene resin contains high-molecular-weight components or long-chain branched components with long relaxation times, the amount of components having a molecular weight of 100,000 or less contained in the polypropylene resin can be easily adjusted without significantly changing the overall viscosity, which makes it easier to improve film formability without significantly affecting rigidity or thermal shrinkage.

[0140] (Molecular weight distribution) The polypropylene resin has a lower limit of the mass average molecular weight (Mw) / number average molecular weight (Mn), which is an index of the breadth of the molecular weight distribution, of preferably 3.5, more preferably 4, even more preferably 4.5, and particularly preferably 5. The upper limit of Mw / Mn is preferably 30, more preferably 25, even more preferably 23, particularly preferably 21, and most preferably 20. Mw / Mn can be obtained using gel permeation chromatography (GPC). When Mw / Mn is in the above range, it is easy to increase the amount of components having a molecular weight of 100,000 or less.

[0141] The molecular weight distribution of the polypropylene resin can be adjusted by polymerizing components of different molecular weights in a series of plants in multiple stages, blending components of different molecular weights offline in a kneader, polymerizing by blending catalysts with different performances, or using a catalyst that can achieve a desired molecular weight distribution. The shape of the molecular weight distribution obtained by GPC may be a gentle molecular weight distribution with a single peak in a GPC chart with the logarithm (log M) of the molecular weight (M) on the horizontal axis and the differential distribution value (weight fraction per log M) on the vertical axis, or may be a molecular weight distribution with multiple peaks or shoulders.

[0142] (Film Thickness) The thickness of the biaxially oriented polypropylene film for the thin film manufacturing process is set according to each application. To obtain film strength, the lower limit of the film thickness is preferably 5 μm, more preferably 8 μm, even more preferably 10 μm, particularly preferably 12 μm, and most preferably 14 μm. A film thickness of 5 μm or more facilitates obtaining rigidity of the film, facilitating the application of a thin film layer, and facilitating peeling of the thin film layer. Furthermore, wrinkles are less likely to occur during winding. The upper limit of the film thickness is preferably 120 μm, more preferably 100 μm, even more preferably 80 μm, particularly preferably 70 μm, and most preferably 60 μm. A film thickness of 120 μm or less is less likely to reduce the cooling rate of the unstretched sheet during the extrusion process. Biaxially oriented polypropylene film for the thin film manufacturing process is typically produced as a roll having a width of approximately 2,000 to 12,000 mm and a length of approximately 1,000 to 50,000 m, and then wound into a film roll. The film is then slit to fit the intended use and supplied as a slit roll with a width of 300 to 2,000 mm and a length of 500 to 5,000 m. Biaxially oriented polypropylene film for thin film manufacturing processes can be used to obtain even longer film rolls.

[0143] (Thickness Uniformity) The lower limit of the thickness uniformity of biaxially oriented polypropylene film for thin film manufacturing processes is preferably 0%, more preferably 0.1%, even more preferably 0.5%, and particularly preferably 1%. The upper limit of the thickness uniformity is preferably 20%, more preferably 17%, even more preferably 15%, particularly preferably 12%, and most preferably 10%. Within the above range, defects are less likely to occur during post-processing such as coating or printing, making it suitable for applications requiring precision. The thickness uniformity can be measured, for example, as follows: A 40 mm test piece is cut out from a steady region of the film where the film properties are stable in the length direction, and the film thickness is measured continuously over 20,000 mm using a film feeder manufactured by Micron Measuring Instruments Co., Ltd. (product number: A90172) and a continuous film thickness measuring instrument manufactured by Anritsu Corporation (product name: K-313A wide-range high-sensitivity electronic micrometer). Furthermore, the maximum, minimum, and average thickness values ​​are determined, and the thickness uniformity can be calculated using the following formula: Thickness uniformity (%) = [(maximum thickness - minimum thickness) / average thickness] x 100

[0144] (Film characteristics) The biaxially oriented polypropylene film for thin film production processes preferably has the following characteristics and structure. Here, the "longitudinal direction" of the biaxially oriented polypropylene film for thin film production processes refers to the direction corresponding to the flow direction in the film production process, and the "width direction" refers to the direction perpendicular to the flow direction in the film production process. For polypropylene films whose flow direction in the film production process is unknown, wide-angle X-rays are incident perpendicular to the film surface, and scattering peaks derived from the (110) plane of the α-crystals are scanned in the circumferential direction. The direction with the greatest diffraction intensity in the obtained diffraction intensity distribution is defined as the "longitudinal direction," and the direction perpendicular to that is defined as the "width direction."

[0145] (Crystalline component (I), constrained amorphous component (II), unconstrained amorphous component (III) determined by pulsed NMR) １It is known that the decay time constant of the FID (Free Induction Decay) of the spin-spin relaxation time T2 observed by H-pulse NMR is observed as the sum of two or more decay time constants. For example, according to Polymer Journal, Vol. 3, No. 4, pp. 448-462 (1972), the decay time constant of the relaxation time of a crystalline polymer is analyzed by the solid echo method of pulse NMR as the sum of the three components: the crystalline component, the mesophase component, and the amorphous component. １ The spin-spin relaxation time T2 observed by H-pulse NMR becomes slower in the order of crystalline, mesophase, and amorphous. The mesophase has a faster T2 than the amorphous phase, and is considered to be an amorphous phase with restricted mobility. When stretching is performed while disentangling the molecular chains, a crystalline component (I) with strong orientation is generated, and an amorphous chain component (II) with restricted mobility (corresponding to the mesophase) is generated near the crystal. On the other hand, when entanglement is high and a disordered orientation is achieved during stretching, an amorphous component (III) (corresponding to the amorphous component) that is not restricted by the crystal is likely to be generated. The unrestricted amorphous component (III) has high mobility and is likely to move to relieve strain at high temperatures, which is thought to be the cause of shrinkage at high temperatures. On the other hand, the restricted amorphous chain (II) is considered to be less likely to shrink at high temperatures because its movement is suppressed even at high temperatures compared to the amorphous component (III).

[0146] The upper limit of the ratio of the unconstrained amorphous component (III) in a biaxially oriented polypropylene film for thin film production processes, as determined by pulse NMR, is preferably 7%, more preferably 6%, and even more preferably 5%. In order to reduce the ratio of the unconstrained amorphous component (III), it is particularly effective to increase the area ratio during film production and, after sequential biaxial stretching, to perform another stretching in the width direction at a high temperature. It is also effective to use a polypropylene raw material with a high mesopentad fraction. Furthermore, it is effective to set the lower limit of the amount of components with a molecular weight of 100,000 or less to 35% by mass when measuring the gel permeation chromatography (GPC) integration curve of the polypropylene resin constituting the film. A ratio of the unconstrained amorphous component (III) of 7% or less as determined by pulse NMR means that there are few molecular chains with large distortions in molecular orientation restrained by entanglement points, and the film is less likely to shrink even when crystal melting begins. As a result, even when the release layer or thin film layer is dried at high temperatures, or when the thin film layer is heat-treated, wrinkles are less likely to occur in the laminate of the film or thin film layer, and the film is less susceptible to dimensional change and deterioration in flatness.

[0147] When the ratio of the unconstrained amorphous component (III) determined by pulse NMR using the solid echo method is separated into crystalline component (I), constrained amorphous component (II), and unconstrained amorphous component (III), if the ratio of the unconstrained amorphous component (III) exceeds 7%, there are many molecular chains with large distortion in molecular orientation constrained by entanglement points, and therefore shrinkage occurs simultaneously with the start of crystal melting, resulting in a film prone to wrinkles, dimensional changes, and deterioration of flatness. There is no particular lower limit for the ratio of the unconstrained amorphous component (III), but a practical value is 0.1% or more. If the ratio of the unconstrained amorphous component (III) is attempted to be less than 0.1%, it is necessary to further stretch the film in the width direction at a higher temperature after sequential biaxial stretching, which may reduce the tension during stretching due to melting, resulting in breakage. Furthermore, the crystalline orientation in the film may be weakened, resulting in reduced rigidity.

[0148] (Heat shrinkage at 150°C) The upper limit of the heat shrinkage in the longitudinal direction of the biaxially oriented polypropylene film for thin film production processes at 150°C is preferably 10%, more preferably 8.0%, even more preferably 6.0%, particularly preferably 5.0%, and most preferably 4.0% or less. The lower limit may be 0%, 1.0%, or 2.0%. The upper limit of the heat shrinkage in the width direction at 150°C is preferably 25%, more preferably 20%, even more preferably 16%, even more preferably 15%, particularly preferably 12%, and most preferably 10%. The lower limit may be 0%, 2.0%, or 4.0%. When the longitudinal heat shrinkage rate is 10% or less and the widthwise heat shrinkage rate is 25% or less, wrinkles, dimensional changes, and deterioration of flatness due to heat during release processing or processing of the thin film layer, such as providing a thin film layer or heat treatment, are less likely to occur. In particular, when the longitudinal heat shrinkage rate at 150°C is 8.0% or less and the widthwise heat shrinkage rate at 150°C is 15% or less, the control range of the roll tension during processing is further expanded, resulting in less wrinkles, dimensional changes, and deterioration of flatness, which is preferable. In addition, because the film shrinks less, uneven release properties and uneven thin film layer properties due to uneven heating are less likely to occur. To reduce the heat shrinkage rate at 150°C, it is effective to set the lower limit of the amount of components with a molecular weight of 100,000 or less to 35% by mass when measuring the gel permeation chromatography (GPC) integrated curve of the polypropylene resin constituting the film.

[0149] (F5: stress at 5% elongation at 23 ° C.) The lower limit of the stress at 5% elongation (F5) in the width direction of the biaxially oriented polypropylene film in the thin film manufacturing process at 23 ° C. is preferably 110 MPa, more preferably 120 MPa, even more preferably 140 MPa, even more preferably 160 MPa, particularly preferably 180 MPa, and most preferably 190 MPa. The upper limit of F5 in the width direction at 23 ° C. is preferably 300 MPa, more preferably 290 MPa, and even more preferably 280 Pa. If it is 280 MPa or less, practical manufacturing is easy and the longitudinal-width balance is likely to be improved.

[0150] The lower limit of the F5 in the longitudinal direction of the biaxially oriented polypropylene film for thin film production at 23°C is preferably 40 MPa, more preferably 42 MPa, even more preferably 46 MPa, and particularly preferably 48 MPa. The upper limit of the F5 in the longitudinal direction at 23°C is preferably 70 MPa, more preferably 65 MPa, even more preferably 62 MPa, and particularly preferably 60 MPa. At 70 MPa or less, practical production becomes easier and the longitudinal-width balance tends to improve. By setting the F5 at the above level or higher, the high rigidity makes it easier to maintain the film shape and facilitates release processing, as well as facilitating handling during processing of the thin film layer and peeling of the thin film, and dimensional change and deterioration of flatness are less likely to occur, making it easier to obtain a uniform, high-quality thin film. F5 can be kept within the range by adjusting the stretching ratio and relaxation rate, or adjusting the temperature during film production.

[0151] The widthwise heat shrinkage (%) at 150°C and the widthwise stress at 5% elongation (MPa) at 23°C of the biaxially oriented polypropylene film for thin film manufacturing processes preferably satisfy the following formula: Widthwise heat shrinkage (%) at 23°C at 5% elongation (MPa) ≥ Widthwise heat shrinkage (%) at 150°C × 4.0 + 140. This results in higher rigidity and a smaller heat shrinkage at high temperatures, making it easier to maintain the shape of the film and reducing heat-induced wrinkles in the film during the drying process of the release layer. Furthermore, during release processing, thin film layer processing such as providing a thin film layer or heat treatment, the film and the laminate with the thin film layer are less likely to wrinkle, change in dimension, or have poor flatness, making handling easier and facilitating the production of uniform, high-quality thin films. Wrinkles are caused by heat-induced film shrinkage and film deformation due to tension during roll transport; optimizing the balance between these two factors can reduce wrinkles. Furthermore, the control range of the roll tension during processing is wider, which is preferable because it results in less wrinkling, dimensional change, and poor flatness. Furthermore, it becomes possible to make films thinner for thin film manufacturing processes, which also contributes to reducing the volume of the film.

[0152] Furthermore, it is preferable that the heat shrinkage (%) in the width direction at 150°C and the stress (MPa) at 5% elongation in the width direction at 23°C of the biaxially oriented polypropylene film for thin film manufacturing process satisfy the following formula: Stress (MPa) at 5% elongation in the width direction at 23°C ≥ Heat shrinkage (%) in the width direction at 150°C × 4.0 + 150

[0153] Furthermore, it is more preferable that the heat shrinkage (%) in the width direction at 150°C and the stress (MPa) at 5% elongation in the width direction at 23°C of the biaxially oriented polypropylene film for thin film manufacturing process satisfy the following formula: Stress (MPa) at 5% elongation in the width direction at 23°C ≥ Heat shrinkage (%) in the width direction at 150°C × 4.0 + 160

[0154] (Heat shrinkage at 120°C) The upper limit of the longitudinal heat shrinkage at 120°C of the biaxially oriented polypropylene film for thin film production process is preferably 2.0%, more preferably 1.5%, even more preferably 1.2%, particularly preferably 1.0%, and most preferably 0.8%. The lower limit may be 0% or 0.1%. When it is 2.0% or less, poor appearance such as vertical streaks during release processing is less likely to occur. The upper limit of the widthwise heat shrinkage at 120°C is preferably 8.0%, more preferably 5.0%, even more preferably 3.5%, even more preferably 2.5%, particularly preferably 2.0%, even more particularly preferably 1.5%, and most preferably 1.0%. The lower limit may be 0%, 0.1%, or 0.2%. When it is less than the above, wrinkles, dimensional changes, and deterioration of flatness are less likely to occur in the film or laminate with the thin film during release processing or processing of the thin film layer, not only improving the appearance but also making it easier to obtain a uniform, high-quality thin film. The heat shrinkage rate at 120°C can be kept within the range by adjusting the stretching ratio, stretching temperature and heat setting temperature.

[0155] It is preferable that the widthwise heat shrinkage (%) at 120°C and the widthwise tensile modulus (GPa) at 23°C of the biaxially oriented polypropylene film for thin film production processes satisfy the following formula: Widthwise tensile modulus (GPa) ≥ Widthwise heat shrinkage (%) at 120°C × 0.3 + 7.0 This results in higher rigidity and a smaller heat shrinkage at high temperatures, which makes it less likely for wrinkles, dimensional changes, or deterioration in flatness to occur in the film or laminate with the thin film during release processing and processing of the thin film layer, not only improving the appearance but also making it easier to obtain a uniform, high-quality thin film.

[0156] It is more preferable that the heat shrinkage (%) in the width direction at 120°C and the tensile modulus (GPa) in the width direction at 23°C of the biaxially oriented polypropylene film for thin film manufacturing process satisfy the following formula: tensile modulus (GPa) in the width direction at 23°C ≥ heat shrinkage (%) in the width direction at 120°C × 0.3 + 8.0

[0157] Furthermore, it is more preferable that the heat shrinkage (%) in the width direction at 120°C and the tensile modulus (GPa) in the width direction at 23°C of the biaxially oriented polypropylene film for thin film manufacturing process satisfy the following formula: tensile modulus (GPa) in the width direction at 23°C ≥ heat shrinkage (%) in the width direction at 120°C × 0.3 + 9.0

[0158] (Tensile modulus at 23°C) The lower limit of the longitudinal tensile modulus of the biaxially oriented polypropylene film for thin film production processes at 23°C is preferably 2.0 GPa, more preferably 2.1 GPa, even more preferably 2.2 GPa, still more preferably 2.3 GPa, particularly preferably 2.4 GPa, and most preferably 2.6 GPa. The upper limit of the longitudinal tensile modulus is preferably 4.0 GPa, more preferably 3.8 GPa, even more preferably 3.7 GPa, particularly preferably 3.6 GPa, and most preferably 3.5 GPa. At 4.0 GPa or less, practical production is easy and the balance of properties in the longitudinal and width directions is likely to be improved.

[0159] The lower limit of the widthwise tensile modulus of the biaxially oriented polypropylene film for thin film production processes at 23°C is preferably 5.0 GPa, more preferably 6.0 GPa, even more preferably 6.5 GPa, even more preferably 6.7 GPa, particularly preferably 7.0 GPa, even more particularly preferably 8.0 GPa, and most preferably 8.5 GPa. The upper limit of the widthwise tensile modulus is preferably 15 GPa, more preferably 13 GPa, and even more preferably 12 GPa. A modulus of 15 GPa or less facilitates practical production and improves the balance of longitudinal and widthwise properties. By setting the tensile modulus at the above level or higher, the film shape is easily maintained, and it is less likely to stretch even when strong tension is applied to the film when providing, processing, or transferring the thin film layer. This makes it easier to handle the film when processing or transferring the thin film layer, and the film or the laminate with the thin film layer is less likely to wrinkle, change in dimension, or deteriorate in flatness. This not only improves the appearance quality but also facilitates the production of uniform, high-quality thin films. The tensile modulus can be kept within the range by adjusting the stretching ratio and relaxation rate, or by adjusting the temperature during film formation.

[0160] (Tensile breaking strength at 23°C) The lower limit of the longitudinal tensile breaking strength of the biaxially oriented polypropylene film for thin film production process at 23°C is preferably 90 MPa, more preferably 100 MPa, even more preferably 110 MPa, and particularly preferably 115 MPa. The upper limit of the longitudinal tensile breaking strength is preferably 200 MPa as a practical value, more preferably 180 MPa, and even more preferably 160 MPa. If it is 200 MPa or less, the film is less likely to break.

[0161] The lower limit of the widthwise tensile breaking strength of the biaxially oriented polypropylene film for thin film production processes at 23°C is preferably 250 MPa, more preferably 300 MPa, even more preferably 350 MPa, even more preferably 400 MPa, particularly preferably 420 MPa, even more particularly preferably 440 MPa, and most preferably 450 MPa. The upper limit of the widthwise tensile breaking strength is preferably 650 MPa as a practical value, more preferably 600 MPa, and even more preferably 550 MPa. At 650 MPa or less, film breakage is likely to be reduced. At a tensile breaking strength above the above range, high tension is easily applied during release processing, when forming a thin film layer, or during processing, making the film or laminate less susceptible to wrinkling, dimensional change, and deterioration of flatness, making handling easier. This not only improves appearance quality but also facilitates the production of uniform, high-quality thin films. Furthermore, film breakage during release processing is less likely to occur. The tensile breaking strength can be kept within the range by adjusting the stretch ratio, stretching temperature, and heat setting temperature.

[0162] (Tensile elongation at break at 23°C) The lower limit of the longitudinal tensile elongation at break of the biaxially oriented polypropylene film for thin film production process at 23°C is preferably 150%, more preferably 180%, even more preferably 190%, particularly preferably 200%, and most preferably 210%. If it is 150% or more, the film is likely to break less. The upper limit of the longitudinal tensile elongation at break at 23°C is preferably 300% as a practical value, more preferably 280%.

[0163] The lower limit of the tensile elongation at break in the width direction of the biaxially oriented polypropylene film for thin film manufacturing processes at 23°C is preferably 15%, more preferably 20%, even more preferably 25%, and particularly preferably 30%. If it is 15% or more, the film is less likely to break. The upper limit of the tensile elongation at break in the width direction at 23°C is preferably 60%, more preferably 55%, and even more preferably 50%. The tensile elongation at break can be kept within the range by adjusting the stretch ratio, stretching temperature, and heat setting temperature.

[0164] (Refractive Index) The lower limit of the refractive index (Nx) in the longitudinal direction of the biaxially oriented polypropylene film for thin film manufacturing processes is preferably 1.4950, more preferably 1.4970, even more preferably 1.4980, particularly preferably 1.4990, and most preferably 1.5000. If it is 1.4950 or higher, the rigidity of the film is likely to be increased. The upper limit of the refractive index (Nx) in the longitudinal direction is preferably 1.5100, more preferably 1.5070, and even more preferably 1.5050. If it is 1.5100 or lower, the film is likely to have an excellent balance of properties in the longitudinal direction and the width direction.

[0165] The lower limit of the refractive index (Ny) in the width direction of the biaxially oriented polypropylene film for thin film manufacturing processes is preferably 1.5250, more preferably 1.5253, even more preferably 1.5255, still more preferably 1.5260, and particularly preferably 1.5265. If it is 1.5250 or higher, the rigidity of the film tends to be increased. The upper limit of the refractive index (Ny) in the width direction is preferably 1.5280, more preferably 1.5275, and even more preferably 1.5270. If it is 1.5280 or lower, the film tends to have an excellent balance of properties in the longitudinal direction and the width direction.

[0166] The lower limit of the refractive index (Nz) in the thickness direction of the biaxially oriented polypropylene film for thin film manufacturing processes is preferably 1.4960, more preferably 1.4965, even more preferably 1.4970, particularly preferably 1.4980, and most preferably 1.4990. If it is 1.4960 or higher, the rigidity of the film is likely to be increased. The upper limit of the refractive index (Nz) in the thickness direction is preferably 1.5020, more preferably 1.5015, and even more preferably 1.5010. If it is 1.5020 or lower, the heat resistance of the film is likely to be increased. The refractive index can be kept within the range by adjusting the stretch ratio, stretching temperature, and heat setting temperature.

[0167] (ΔNy) The lower limit of ΔNy of the biaxially oriented polypropylene film for thin film manufacturing processes is preferably 0.0240, more preferably 0.0245, even more preferably 0.0247, even more preferably 0.0250, particularly preferably 0.0255, and most preferably 0.0260. If it is 0.0240 or higher, the rigidity of the film tends to be high. The upper limit of ΔNy is preferably 0.0280 as a practical value, more preferably 0.0277, even more preferably 0.0273, and particularly preferably 0.0270. If it is 0.0280 or lower, thickness unevenness tends to be improved. ΔNy can be kept within the range by adjusting the film stretch ratio, stretching temperature, and heat setting temperature. ΔNy is calculated using the following formula, where Nx, Ny, and Nz are the refractive indices along the length, width, and thickness directions of the film, respectively, and means the degree of orientation in the width direction relative to the overall orientation in the length, width, and thickness directions of the film: ΔNy=Ny-[(Nx+Nz) / 2]

[0168] (Plane Orientation Coefficient) The lower limit of the plane orientation coefficient (ΔP) of biaxially oriented polypropylene film for thin film manufacturing processes is preferably 0.0135, more preferably 0.0138, and even more preferably 0.0140. At 0.0135 or higher, the film has a good balance in the plane direction and good thickness uniformity. The upper limit of the plane orientation coefficient (ΔP) is preferably 0.0155 as a practical value, more preferably 0.0152, and even more preferably 0.0150. At 0.0155 or lower, excellent heat resistance at high temperatures is likely to be achieved. The plane orientation coefficient (ΔP) can be kept within the range by adjusting the stretch ratio, stretching temperature, and heat setting temperature. The plane orientation coefficient (ΔP) is calculated using the formula [(Nx + Ny) / 2] - Nz.

[0169] (Average Refractive Index) The lower limit of the average refractive index of the biaxially oriented polypropylene film for thin film manufacturing processes is preferably 1.5080, more preferably 1.5081, even more preferably 1.5082, particularly preferably 1.5083, and most preferably 1.5090. The upper limit of the average refractive index is preferably 1.5150, more preferably 1.5140, even more preferably 1.5135, and particularly preferably 1.5130, as a practical value. A refractive index of 1.5080 or higher makes the film or laminate less susceptible to wrinkling, dimensional changes, and deterioration of flatness during release processing and thin film layer processing, making handling easier. This not only improves appearance quality, but also facilitates the production of uniform, high-quality thin films. The average refractive index can be kept within this range by adjusting the film stretch ratio, stretching temperature, and heat setting temperature. The average refractive index is calculated using the following formula, where Nx, Ny, and Nz are the refractive indices along the longitudinal, width, and thickness directions of the film, respectively. Average refractive index=(Nx+Ny+Nz) / 3

[0170] (Haze) When transparency is required for the biaxially oriented polypropylene film for thin film production processes, the upper limit of the film haze is preferably 5.0%, more preferably 4.5%, even more preferably 4.0%, particularly preferably 3.5%, and most preferably 3.0%. A haze of 5.0% or less is easy to use in applications requiring transparency. The lower limit of the haze is preferably 0.1%, more preferably 0.2%, even more preferably 0.3%, and particularly preferably 0.4% as a practical value. A haze of 0.1% or more is easy to manufacture. The haze can be kept within the range by adjusting the chill roll (CR) temperature, width direction stretching temperature, tenter preheating temperature before width direction stretching, width direction stretching temperature, or heat setting temperature, or the amount of components of the polypropylene resin with a molecular weight of 100,000 or less. However, the haze may increase by adding an antiblocking agent or providing a sealing layer.

[0171] (Half-width of diffraction peak derived from oriented crystals) In the azimuth angle dependence of the scattering peak of the (110) plane of polypropylene α-crystals obtained by wide-angle X-ray measurement of biaxially oriented polypropylene film for thin film manufacturing process, the upper limit of the half-width (Wh) of the diffraction peak derived from oriented crystals in the width direction of the film is preferably 30 °, more preferably 28 °, even more preferably 26 °, even more preferably 25 °, particularly preferably 24 °, more particularly preferably 23 °, and most preferably 22.0 °. When the half-width (Wh) is 30 ° or less, particularly 26 ° or less, the rigidity of the film is easily increased. The lower limit of the half-width (Wh) is preferably 15 °, more preferably 16 °, and even more preferably 17 °.

[0172] (X-ray orientation degree) The lower limit of the X-ray orientation degree calculated from the half-width (Wh) of the biaxially oriented polypropylene film for thin film manufacturing process using the following formula is preferably 0.833, more preferably 0.844, even more preferably 0.856, even more preferably 0.861, particularly preferably 0.867, even more particularly preferably 0.872, and most preferably 0.878. By making it 0.833 or more, especially 0.856 or more, it is easy to increase rigidity. X-ray orientation degree = (180 - Wh) / 180 The upper limit of the X-ray orientation degree is preferably 0.917, more preferably 0.911, and even more preferably 0.906. By making it 0.917 or less, film production is easy to stabilize.

[0173] (Loop Stiffness Stress) In a biaxially oriented polypropylene film for thin film manufacturing processes, the relationship between the widthwise loop stiffness stress S [mN] and the thickness t (μm) satisfies the following formula (A). In other words, as in the examples described below, when the cube of the thickness t (μm) is plotted on the horizontal axis and the widthwise loop stiffness stress [mN] on the vertical axis, and linear approximation is performed using the least squares method so that the intercept is 0, and the slope a of the approximated line is determined, the slope a is 0.0010 or more. The loop stiffness stress is an index that represents the stiffness of a film, and although it also depends on the thickness of the film, the value of the slope a of the approximated line represents a characteristic value specific to the film that is independent of the thickness and determines the rigidity. S≧0.0010×t ３...(A)

[0174] The lower limit of the loop stiffness stress S (mN) in the width direction of the biaxially oriented polypropylene film for the thin film manufacturing process at 23°C is 0.0010 x t (μm), where t is the thickness of the biaxially oriented polypropylene film. ３ and preferably 0.0011 × t ３ and particularly preferably 0.0012 × t ３ and most preferably 0.0013 × t ３ 0.0010 x t ３ If the film has a thickness of 1 / 2 mm or more, the peeling force during peeling of the thin film is likely to be small, allowing for smooth peeling and preventing breakage of the thin film. In addition, since the film has high rigidity, wrinkles and deformations are unlikely to occur during release processing or processing of the thin film layer, allowing for stable processing, which not only improves the appearance quality but also makes it easy to produce a uniform, high-quality thin film. The upper limit of the loop stiffness stress S (mN) in the width direction at 23°C is preferably 0.0020 x t ３ and more preferably 0.0019 × t ３ and more preferably 0.0018 × t ３ and particularly preferably 0.0017 × t ３ 0.0020 x t ３ If it is less than this, it is easy to manufacture in practice.

[0175] It is preferable that the relationship between the longitudinal loop stiffness stress S [mN] and the thickness t (μm) of the biaxially oriented polypropylene film for thin film manufacturing processes satisfies the following formula (B). In other words, as in the examples described later, when the cube of the thickness t (μm) is plotted on the horizontal axis and the longitudinal loop stiffness stress S [mN] on the vertical axis, and linear approximation is performed using the least squares method so that the intercept is 0, and the slope a of the approximate line is determined, it is preferable that the slope a is 0.00030 or more. The following formula (B) is explained below. S≧0.00030×t ３ ...(B)

[0176] The lower limit of the longitudinal loop stiffness stress S (mN) of the biaxially oriented polypropylene film for the thin film manufacturing process at 23°C is preferably 0.00030 x t (μm), where t is the thickness of the biaxially oriented polypropylene film.３ and more preferably 0.00040 × t ３ and more preferably 0.00045 × t ３ and particularly preferably 0.00048 × t ３ and most preferably 0.00050 × t ３ 0.00030 x t ３ If the film has a thickness of 1000 nm or more, the peeling force when peeling the thin film from the film is likely to be small, allowing for smooth peeling and reducing the occurrence of peel marks (streaky marks that occur when the film is caught during peeling). Furthermore, since the film has high rigidity, wrinkles and deformations are unlikely to occur during release processing or thin film layer processing, allowing for stable processing, which not only improves the appearance quality but also facilitates the production of uniform, high-quality thin films. The upper limit of the longitudinal loop stiffness stress S (mN) at 23°C is preferably 0.00080 x t ３ and more preferably 0.00075 × t ３ and more preferably 0.00072 × t ３ and particularly preferably 0.00070 × t ３ 0.00080 x t ３ If it is less than this, it is easy to manufacture in practice.

[0177] (Method for producing biaxially oriented polypropylene film for thin film production process) The biaxially oriented polypropylene film for thin film production process is preferably obtained by producing an unstretched sheet made of a polypropylene resin composition containing the above-mentioned polypropylene resin as a main component, and biaxially stretching the sheet. As the biaxial stretching method, any of the inflation simultaneous biaxial stretching method, tenter simultaneous biaxial stretching method, and tenter sequential biaxial stretching method can be used, but from the viewpoint of film production stability and thickness uniformity, it is preferable to adopt the tenter sequential biaxial stretching method. In particular, it is preferable to stretch in the longitudinal direction and then in the width direction, but a method in which stretching in the width direction and then in the longitudinal direction may also be used.

[0178] The biaxially oriented polypropylene film for thin film manufacturing processes of the embodiment may have a layer having another function laminated on at least one side. Lamination may be performed on one or both sides. In this case, the resin composition of the other layer or the central layer may be the polypropylene resin composition described above. Furthermore, the polypropylene resin composition may be different from the polypropylene resin composition described above. The number of layers to be laminated may be one, two, or three or more per side. From a manufacturing standpoint, one or two layers per side is preferred. Preferred lamination methods include coextrusion using a feed block system or a multi-manifold system. In particular, to improve the handleability of the biaxially oriented polypropylene film for thin film manufacturing processes, a resin layer having easy lubrication or a resin layer having releasability containing particles or the like may be laminated to a degree that does not impair the properties. Furthermore, corona treatment may be performed on one or both sides to adjust the releasability. For other details of the film-forming method for biaxially oriented polypropylene film for thin film manufacturing processes, which is similar to the film-forming method for biaxially oriented polypropylene film for transfer substrates, please refer to the description of the film-forming method for biaxially oriented polypropylene film for transfer substrates in the first disclosure. In that case, "for transfer substrate" shall be read as "for thin film manufacturing process."

[0179] (Release layer-laminated biaxially oriented polypropylene film for thin film manufacturing process) The above-mentioned biaxially oriented polypropylene film for thin film manufacturing process may be used as a film for thin film manufacturing process without any particular release treatment, or the release properties may be adjusted by corona treatment, flame treatment, plasma treatment, etc. Furthermore, the above-mentioned release properties may be adjusted in a gas atmosphere containing a fluorine-based compound or a silicone-based compound. Below, a release layer-laminated biaxially oriented polypropylene film for thin film manufacturing process of an embodiment will be described. The release layer-laminated biaxially oriented polypropylene film for thin film manufacturing process has any of the above-mentioned biaxially oriented polypropylene films for thin film manufacturing process and a release layer laminated on at least one side of the biaxially oriented polypropylene film for thin film manufacturing process.

[0180] When preparing a release layer-laminated biaxially oriented polypropylene film for thin film manufacturing processes, a release agent may be applied to the surface of the biaxially oriented polypropylene film for thin film manufacturing processes. When a release agent is applied to the surface, it is preferable that the surface wet tension of the biaxially oriented polypropylene film for thin film manufacturing processes be 38 mN / m or more. A wet tension of 38 mN / m or more improves adhesion to the release layer. To achieve a wet tension of 38 mN / m or more, physicochemical surface treatments such as corona treatment, flame treatment, and plasma treatment are preferably performed. For example, corona treatment preferably involves using a preheated roll and a treatment roll to discharge in the air. The wet tension is preferably 44 mN / m or less, more preferably 43 mN / m or less, and even more preferably 42 mN / m or less. The wet tension may be less than 38 mN / m when no release agent is applied, and can be adjusted by the surface treatment conditions to achieve the required releasability; surface treatment may not be necessary.

[0181] The release agent may contain silicone resin, fluororesin, alkyd resin, amino resin, various waxes, aliphatic olefin, long-chain alkyl group-containing resin, etc., and each resin may be used alone or in combination of two or more types. The silicone resin used as the release agent may be any silicone resin commonly used in release agents, and may be selected from among the silicone resins commonly used in the relevant field, as described in, for example, "Silicone Materials Handbook" (edited by Toray Dow Corning, August 1993). Generally, heat-curable or ionizing radiation-curable silicone resins (which encompass both resins and resin compositions) are used. Examples of heat-curable silicone resins include condensation reaction and addition reaction silicone resins, and examples of ionizing radiation-curable silicone resins include ultraviolet or electron beam-curable silicone resins. These are applied to the substrate film and dried or cured to form a release layer. For other details about the release agent, which are similar to those used in the transfer release layer-laminated polypropylene film, please refer to the description of the release agent in the first disclosure.

[0182] The resin of the release 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 layer, and the precursor may be subjected to a crosslinking reaction using ultraviolet light, an electron beam, or the like.

[0183] When a release agent is used, it may be used alone or in combination of two or more. To adjust the release force, it is also possible to add an additive such as a light release additive or a heavy release additive. The resulting biaxially oriented polypropylene film having a release layer has particularly excellent releasability.

[0184] The release layer may contain particles with a particle size of 1 μm or less, but preferably does not substantially contain particles or other protrusion-forming materials in terms of pinhole formation. Additives such as adhesion improvers and antistatic agents may be added to the release layer. In addition, in order to improve adhesion to 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 layer.

[0185] The thickness of the release 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 release layer thickness of 0.005 μm or more is preferable because release performance is maintained. Furthermore, a release layer 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. Another layer may be provided between the biaxially oriented polypropylene film and the release layer.

[0186] The method for forming the release layer is not particularly limited. A coating solution containing a release resin dissolved or dispersed therein is applied to one side of a biaxially oriented polypropylene film by coating or the like, and the solution is then dried to remove the solvent, followed by heat drying, heat curing, or UV curing. 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 lower drying temperature may result in insufficient heat curing of the release layer, resulting in insufficient release properties. Generally, biaxially oriented polypropylene films have lower thermal dimensional stability at high temperatures than biaxially oriented polyester films, which means that heat-induced wrinkles and deterioration of flatness are more likely to occur during drying of the coating film. However, the biaxially oriented polypropylene film for thin film manufacturing processes according to the present embodiment can suppress wrinkles. The heat drying time is typically 10 to 60 seconds.

[0187] As a method for applying the coating liquid, any known coating method can be applied, and conventionally known methods such as roll coating methods such as gravure coating and reverse coating, bar coating methods such as wire bar coating, die coating, spray coating, and air knife coating can be used.

[0188] The release layer may be a layer below the thin film layer, or may be a release layer for preventing the thin film layer from sticking to the surface of the biaxially oriented polypropylene film for thin film manufacturing process opposite the thin film layer when the laminate of the biaxially oriented polypropylene film for thin film manufacturing process and the thin film layer is wound into a roll. Also, the release layer may be laminated on both sides of the biaxially oriented polypropylene film.

[0189] The following describes a method for producing a thin film according to an embodiment. The method for producing a thin film according to an embodiment preferably includes step 1A of preparing any of the biaxially oriented polypropylene films for thin film production processes described above, step 1B of providing a thin film layer on at least one surface of the biaxially oriented polypropylene film for thin film production processes, and step 1C of peeling the thin film layer from the biaxially oriented polypropylene film for thin film production processes. The method for producing a thin film according to an embodiment also preferably includes step 2A of preparing any of the release layer-laminated biaxially oriented polypropylene films for thin film production processes described above, step 2B of providing a thin film layer on the release layer surface of the release layer-laminated biaxially oriented polypropylene film for thin film production processes, and step 2C of peeling the thin film layer from the release layer. That is, in the production of a thin film according to an embodiment, it is preferable to prepare a biaxially oriented polypropylene film for thin film production processes, or a release layer-laminated biaxially oriented polypropylene film for thin film production processes having a release layer on at least one surface thereof, and to provide a thin film layer on at least one surface thereof.

[0190] In step 1B of providing a thin film layer on at least one surface of the biaxially oriented polypropylene film for thin film manufacturing processes, it is preferable to apply a coating solution to at least one surface and dry the solvent of the coating solution. Similarly, in step 2B of providing a thin film layer on the release layer surface of the release layer-laminated biaxially oriented polypropylene film for thin film manufacturing processes, it is preferable to apply a coating solution to at least one surface and dry the solvent of the coating solution. Such a dried thin film layer becomes easy to peel from the biaxially oriented polypropylene film or the release layer in step 1C or step 2C.

[0191] The thin film layer is preferably a resin thin film, which may be non-porous or porous. The thin film layer can be formed by spreading a solution or dispersion containing a resin as a raw material and, if necessary, additives on a substrate film and then removing the solvent. This method is generally called a solution method or a casting method.

[0192] Specific examples of the thin film layer include non-porous resin films used as insulating materials, barrier materials, etc., polymer electrolyte membranes used in fuel cells, etc., and porous membranes used in lithium ion batteries, etc. The thin film layer preferably includes any of a resin film, a polymer electrolyte membrane, and a porous membrane.

[0193] Resins that can be used as the material for nonporous resin films include epoxy resins, phenoxy resins, polyester resins, wholly aromatic polyester resins, polyarylate resins, polycarbonate resins, polyurethane resins, fluorine resins, acrylic resins, polyolefin resins, polyimide resins, aromatic polyamide resins, polysulfone resins, polyether resins, polyethersulfone resins, ketone resins, polyetherketone resins, polyacrylonitrile resins, polyamideimide resins, polyaniline resins, polythiophene resins, cellulose resins, etc. These resins often require the use of high-boiling point solvents, and the manufacturing method of the embodiment is preferably applied to them.

[0194] The resin of the resin film may be crosslinked. The crosslinking may be self-crosslinking of the resin itself, or a crosslinking agent may be used. The crosslinking agent is not particularly limited as long as it can react with the reactive group introduced into the resin, and examples thereof include isocyanate compounds, melamine compounds, carbodiimide compounds, oxazoline compounds, epoxy resins, and compounds having multiple double bonds. Crosslinked resin films are difficult to produce using a general melt extrusion method, and may require high temperatures for the crosslinking reaction, so this is an example to which the production method of the embodiment is preferably applied.

[0195] A nonporous resin film can be obtained by dissolving or dispersing the resin material in a solvent, optionally adding a crosslinking agent, a catalyst, or other additives, and applying the coating solution to a substrate film, drying and removing the solvent, and then peeling it off from the substrate. When crosslinking is performed, the crosslinking may be performed while the film is laminated with the substrate film, or after peeling it off from the substrate. Furthermore, if the film can maintain its shape even when it contains a solvent, it may be peeled off from the substrate while still containing the solvent, and then the residual solvent may be removed from the resin film. Furthermore, in the case of polyimide, the precursor may be coated and dried, the precursor film may be peeled off from the substrate film, and then the reaction may be completed.

[0196] The additives include particles, fillers, colorants, antioxidants, antistatic agents, etc. The resin may also be a blend of multiple resins.

[0197] There are no particular restrictions on the solvent that can be used as long as it dissolves the resin, but in order to take advantage of the advantages of the OPP film for thin film production of the embodiment, it is preferable that the solvent contains a solvent with a boiling point of 120°C or higher, more preferably a solvent with a boiling point of 130°C or higher, even more preferably a solvent with a boiling point of 140°C or higher, and particularly preferably a solvent with a boiling point of 150°C or higher.

[0198] These solvents include acetylacetone (141°C), monoethanolamine (171°C), benzyl alcohol (205°C), n-butyl alcohol (117°C), butyl acetate (125°C), dibutyl ether (142°C), cyclohexanol (161°C), cyclohexanone (156°C), diethyl carbonate (127°C), diethylene glycol monobutyl ether (230°C), diethylene glycol monoethyl ether (196°C), diethylene glycol monomethyl ether (194°C), dimethylacetamide (163°C), dimethylformamide (153°C), dimethyl sulfoxide (189°C), N-methylpyrrolidone (202°C), 2-chloroethanol (128°C), ethylene glycol (197°C), ethylene glycol monobutyl ether (171°C), ethylene glycol monobutyl ether acetate (192°C), °C), ethylene glycol monoethyl ether (135 °C), ethylene glycol monoethyl ether acetate (145 °C), 2-ethylhexanol (184 °C), ethyl acetoacetate (180 °C), formamide (210 °C), 1-hexanol (157 °C), 2,6-dimethylpyrrolidone (144 °C), ethylene glycol monomethyl ether (124 °C), 3-methyl-1-butanol (131 °C), 3-methyl acetate Examples include butyl ether (142°C), n-octane (126°C), 1-octanol (195°C), 2-octanol (174°C), 1-pentanol (138°C), n-pentyl acetate (149°C), propylene glycol (187°C), 1,1,2,2-tetrachloroethane (147°C), tetrachloroethylene (121°C), o-xylene (144°C), m-xylene (139°C), and p-xylene (138°C). The boiling points in parentheses are at 1 atmosphere.

[0199] The resin film may be surface-treated while laminated on the substrate film. Examples of surface treatment include corona treatment, plasma treatment, and surface coating. Examples of surface coating include wet processes in which a solution is applied, and dry processes such as vapor deposition and sputter CVD. Typical surface coatings include easy-adhesion coatings and antistatic coatings in wet processes, and application of conductive layers such as gold, copper, aluminum, and ITO in dry processes.

[0200] If the resin film requires processing such as forming a pattern such as a circuit, it may be subjected to post-processing while laminated on a substrate film. Circuit formation can be performed by printing or etching, and the film can be peeled off from the substrate film after the pattern is formed. When the resin film is used by being laminated with another material, it may be attached to the other material while laminated on the substrate film, and then the substrate film may be peeled off.

[0201] The thickness of the nonporous resin film is preferably 0.5 μm or more, more preferably 1.0 μm or more, even more preferably 1.5 μm or more, and particularly preferably 2.0 μm or more. The thickness is preferably 50 μm or less, more preferably 30 μm or less, even more preferably 20 μm or less, and particularly preferably 15 μm or less. Furthermore, with the manufacturing method of the embodiment, even resin films with a thickness of 10 μm or less, 7 μm or less, or 5 μm or less can be manufactured into uniform, high-quality films, and it is also preferable to use the method for manufacturing such thin resin films.

[0202] (Polymer electrolyte membrane) The resin used for polymer electrolyte membrane can be the one that ionic group is introduced into the resin that is the material of the above-mentioned non-porous resin film.Specifically, can be mentioned ionic group-containing polyphenylene oxide, ionic group-containing polyether ketone, ionic group-containing polyether ether ketone, ionic group-containing polyether sulfone, ionic group-containing polyether ether sulfone, ionic group-containing polyether phosphine oxide, ionic group-containing polyether ether phosphine oxide, ionic group-containing polyphenylene sulfide, ionic group-containing polyamide, ionic group-containing polyimide, ionic group-containing polyether imide, ionic group-containing polyimidazole, ionic group-containing polyoxazole, ionic group-containing polyphenylene, etc., aromatic hydrocarbon polymers having ionic group, such as fluoroalkyl ether side chain and fluoroalkyl main chain-containing perfluoro ion-conductive polymers having ionic group.

[0203] Examples of ionic groups include sulfonic acid groups, sulfate groups, sulfonimide groups, phosphonic acid groups, phosphate groups, carboxylic acid groups, and metal salts thereof, with sulfonic acid groups and metal sulfonate salts being preferred. The polymer electrolyte membrane may be crosslinked. The crosslinking method is the same as for the resin film. The polymer electrolyte membrane may also contain the various additives described above, or multiple resins.

[0204] The polymer electrolyte membrane can be obtained by dissolving an ionic group-containing resin in a solvent, optionally adding a crosslinker, a catalyst, or other additives, coating the resulting solution on a substrate film, drying the solvent, and then peeling the resulting solution from the substrate. The solvent preferably contains a high-boiling point solvent such as those listed for the resin film. Alternatively, the precursor may be applied, dried, and then peeled from the substrate film, after which the reaction may be completed.

[0205] The polymer electrolyte membrane is preferably completed by a solvent removal treatment in which the solvent is removed by heating or by desolvation with a liquid miscible with the solvent of the ionic group-containing polymer electrolyte, such as water; an acid treatment in which the ionic groups are converted to an acid form by contact with an inorganic acid-containing acidic liquid, such as hydrochloric acid, nitric acid, or sulfuric acid; an acid removal treatment in which free acid in the membrane is removed by contact with water, etc.; and a final drying treatment. These treatments may be performed after peeling from the substrate, but it is preferable to treat the membrane while it is laminated on the substrate. Note that the final drying treatment is preferably performed while it is laminated on the substrate, but it may also be peeled from the substrate at an intermediate stage. Furthermore, when the polymer electrolyte membrane is bonded to a reinforcing material, etc., it may be bonded to the reinforcing material while it is laminated on a substrate film, and then the substrate film may be peeled off.

[0206] The thickness of the polymer electrolyte membrane is preferably 1.0 μm or more, more preferably 3.0 μm or more, even more preferably 4.0 μm or more, and particularly preferably 5.0 μm or more. The thickness is preferably 100 μm or less, more preferably 70 μm or less, even more preferably 60 μm or less, and particularly preferably 50 μm or less.

[0207] (Porous membrane) A porous membrane can be obtained by applying a solution in which the resin that is the material for the non-porous resin film is dissolved or dispersed in a solvent to a substrate film and making it porous. The method of making it porous is preferably a layer separation method. Specifically, the resin is dissolved in a mixed solvent of a good solvent and a poor solvent for the resin that is the material, and a large amount of the poor solvent remains in the drying process to make the membrane porous. There are also methods in which the solution is applied to a substrate film and then contacted with a poor solvent (coagulation liquid) such as water to make the membrane porous. The solvent preferably contains a high-boiling point solvent listed for the resin film. The porous membrane is then obtained by drying. It may be dried on the substrate film, or it may be peeled off from the substrate film with the solvent remaining and then dried. Alternatively, a precursor may be applied, and the precursor may be made into a porous membrane, which is then peeled off, and the reaction may then be completed.

[0208] When the porous film is to be bonded to another material, the porous film may be bonded to the other material in a state where it is laminated on a substrate film, and then the substrate film may be peeled off. The porous film may also contain the above-mentioned various additives or multiple resins.

[0209] The thickness of the porous membrane is preferably 2.0 μm or more, more preferably 5.0 μm or more, even more preferably 8.0 μm or more, and particularly preferably 10.0 μm or more. The thickness is preferably 200 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, and particularly preferably 70 μm or less.

[0210] The thin film layer may be peeled from the base film and wound up as a thin film, or may be transferred to another material and wound up as a laminate with the other material, etc. Furthermore, until the process of using the thin film, the thin film may be wound up as a laminate of the base film and the thin film layer and stored in a roll.

[0211] As described above, the biaxially oriented polypropylene film for thin film production according to the embodiment is less prone to wrinkles, dimensional changes, or deterioration of flatness during the application or processing of the thin film layer, which not only improves the appearance quality of the resulting thin film, but also facilitates the production of thin films with uniform properties. To make the most of its excellent properties, the biaxially oriented polypropylene film for thin film production according to the embodiment is preferably used when the application or processing of the thin film layer includes a process in a high-temperature environment. Specific processes include a drying process, a crosslinking reaction process, a phase conversion process, a phase separation process, and a surface flattening process.

[0212] Specifically, the temperature preferably includes a step in an environment where the temperature is 110°C or higher, more preferably 115°C or higher, even more preferably 120°C or higher, and particularly preferably 125°C or higher. The upper limit of the environmental temperature is preferably 160°C, more preferably 155°C, and even more preferably 150°C. The lower limit of the time for the step where the temperature is reached is preferably 2 seconds, more preferably 5 seconds, and even more preferably 10 seconds. The upper limit of the time is preferably 60 minutes, more preferably 45 minutes, and even more preferably 30 minutes. However, if the temperature exceeds 155°C, it is preferable to avoid a time of 30 seconds or more, more preferably 20 seconds or more, and even more preferably 15 seconds or more. If the temperature exceeds 150°C, it is preferable to avoid a time of 90 seconds or more, more preferably 60 seconds or more, and even more preferably 45 seconds or more. If the temperature exceeds 140°C, it is preferable to avoid a time of 3 minutes or more, more preferably 2 minutes or more, and even more preferably 1 minute or more. When the temperature exceeds 130°C, it is preferable to avoid a time of 5 minutes or more, more preferably 4 minutes or more, and even more preferably 3 minutes or more. When a heating body such as a heat roll is used for contact, the temperature of the heating body is preferably 120°C or more, more preferably 125°C or more, and even more preferably 130°C or more. The temperature of the heating body is preferably 160°C or less, more preferably 155°C or less, and even more preferably 150°C or less.

[0213] When the thin film layer is provided on the film by melting using a melt extrusion method or the like, the temperature of the molten thin film layer is preferably 180°C or less, more preferably 170°C or less, even more preferably 160°C or less, particularly preferably 150°C or less, and most preferably 145°C or less. However, if the temperature exceeds 150°C, it is preferable to pass the film through a cooling roll or cooling belt and cool it from the opposite side. The temperature of the molten thin film layer is preferably 120°C or more, more preferably 125°C or more, and even more preferably 130°C or more.

[0214] When contacting with a heating body such as a heat roll, the temperature of the heating body is preferably 120°C or higher, more preferably 125°C or higher, and even more preferably 130°C or higher. The temperature of the heating body is preferably 160°C or lower, more preferably 155°C or lower, and even more preferably 150°C or lower. The contact time with the heating body is preferably 0.5 seconds or higher, more preferably 1 second or higher, even more preferably 1.5 seconds or higher, and particularly preferably 2 seconds or higher. The contact time is preferably 180 seconds or lower, more preferably 120 seconds or lower, even more preferably 90 seconds or lower, and particularly preferably 60 seconds or lower. However, if the temperature of the heating body exceeds 155°C, it is preferable to avoid a time of 90 seconds or higher, and if it exceeds 150°C, it is preferable to avoid a time of 60 seconds or higher.

[0215] The thin film manufacturing film is preferably wound into a roll in a long length. When wound into a roll, a masking film (surface protection film) may be attached to protect the surface. Examples of the masking film include polyester-based films, polypropylene-based films, and polyethylene-based films. The masking film may be provided with a release layer and an adhesive layer.

[0216] This application claims the benefit of priority based on Japanese Patent Application Nos. 2023-103777 and 2023-103779, filed on June 23, 2023. The entire contents of the specifications of Japanese Patent Application Nos. 2023-103777 and 2023-103779, filed on June 23, 2023, are incorporated herein by reference.

[0217] The present disclosure will be described in detail below with reference to examples, but the present disclosure is not limited to the following examples and may be modified within the scope of the above and below-described aims.

[0218] (Example of the First Disclosure) The properties were measured and evaluated by the following methods: (1) Melt Flow Rate The melt flow rate (MFR) was measured in accordance with JIS K7210 at a temperature of 230° C. and a load of 2.16 kgf.

[0219] (2) Mesopentad fraction The mesopentad fraction ([mmmm]%) of a polypropylene resin is 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.

[0220] (3) Number average molecular weight, weight average molecular weight, amount of components with molecular weights of 100,000 or less, and molecular weight distribution of polypropylene resin. Gel permeation chromatography (GPC) was used to determine the molecular weight in terms of PP 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 (Tosoh Corporation) Detector: RI Solvent: 1,2,4-trichlorobenzene + dibutylhydroxytoluene (0.05%) Column: TSK gelguard column HHR (30) HT (7.5 mm I.D. x 7.5 cm) x 1 + TSK gel GMHHR-H (20) HT (7.8 mm I.D. x 30 cm) x 3 Flow rate: 1.0 mL / min Injection volume: 0.3 mL Measurement temperature: 140°C The number average molecular weight (Mn) and mass average molecular weight (Mw) are defined by the following equations, where Mn is the number of molecules (Ni) at each elution position of the molecular weight (Mi) on the GPC curve obtained via the molecular weight calibration curve. Number average molecular weight: Mn = Σ(Ni.Mi) / ΣNi Mass average molecular weight: Mw = Σ(Ni.Mi) ２ ) / Σ(Ni·Mi) Here, the molecular weight distribution can be obtained by Mw / Mn. Furthermore, the proportion (mass%) of components having a molecular weight of 100,000 or less was determined from the integral curve of the molecular weight distribution obtained by GPC.

[0221] (4) Crystallization temperature (Tc), melting temperature (Tm) Thermal measurements were performed under a nitrogen atmosphere using a TA Instruments Q1000 differential scanning calorimeter. Approximately 5 mg was cut out from a polypropylene resin pellet and sealed in an aluminum pan for measurement. The temperature was raised to 230 ° C and held for 5 minutes, then cooled to 30 ° C at a rate of -10 ° C / min, and the exothermic peak temperature was taken as the crystallization temperature (Tc). The heat of crystallization (ΔHc) was determined by setting a baseline so that the area of ​​the exothermic peak smoothly connected from the start of the peak to the end of the peak. The sample was then held at 30 ° C for 5 minutes, heated to 230 ° C at 10 ° C / min, and the main endothermic peak temperature was taken as the melting temperature (Tm).

[0222] (5) Film Thickness The film thickness was measured using a Millitron 1202D manufactured by Seiko EM Corporation.

[0223] (6) Haze: Measured at 23° C. in accordance with JIS K7105 using an NDH5000 manufactured by Nippon Denshoku Industries Co., Ltd.

[0224] (7) Tensile Test The tensile strength of the film in the longitudinal and transverse directions was measured at 23°C in accordance with JIS K7127. Samples were cut out from the film to a size of 15 mm x 200 mm and placed in a tensile tester (Instron 5965, a dual-column tabletop tester manufactured by Instron Japan Co., Ltd.) with a chuck distance of 100 mm. The tensile test was performed at a tensile speed of 200 mm / min. From the obtained strain-stress curve, the tensile modulus was calculated from the slope of the linear portion at the initial stage of elongation, and the stress at 5% elongation was designated as F5. The tensile breaking strength and tensile breaking elongation were defined as the strength and elongation, respectively, at the time the sample broke.

[0225] (8) Heat shrinkage was measured according to JIS Z1712 by the following method. The film was cut into pieces of 20 mm width and 200 mm length in both the longitudinal and transverse directions of the film, and then hung in a hot air oven at 120°C or 150°C for 5 minutes. The length after heating was measured, and the heat shrinkage was calculated as the ratio of the shrunk length to the original length.

[0226] (9) Refractive index, ΔNy, plane orientation coefficient, average refractive index The refractive index was measured at a wavelength of 589.3 nm and a temperature of 23°C using an Abbe refractometer manufactured by Atago Co., Ltd. The refractive indices along the longitudinal and width directions of the film were designated Nx and Ny, respectively, and the refractive index along the thickness direction was designated Nz. ΔNy was calculated using Nx, Ny, and Nz using the formula Ny-[(Nx+Nz) / 2]. The plane orientation coefficient (ΔP) was calculated using the formula [(Nx+Ny) / 2]-Nz. The average refractive index was calculated using the formula (Nx+Ny+Nz) / 3.

[0227] (10) X-ray half-width and degree of X-ray orientation: Measurements were made by the transmission method using an X-ray diffractometer (SmartLab, manufactured by Rigaku Corporation, with an αβγ attachment). X-rays with a wavelength of 1.5418 Å were used, with an X-ray output of 45 kV and 200 mA. A hybrid multidimensional pixel detector, Hypix-3000, was used in zero-dimensional mode. A 2.5° solar slit, a 10 mm longitudinal limiting slit, and a 1 mm entrance slit width were used as the incident slit in the parallel beam method. A 0.228° parallel slit analyzer was used as the receiving slit. The camera length was 300 mm, and the detector integral width was 2 mm. The sample was prepared by stacking films to a thickness of 400 μm. A detector was placed at the diffraction peak position (diffraction angle 2θ = 14.1°) of the (110) plane of the α-crystals of the polypropylene resin, and the sample was rotated 360° around the axis in the thickness direction of the film to obtain the azimuth angle dependence of the diffraction intensity of the (110) plane. Measurements were performed at a step interval of 0.5° and a measurement speed of 60° / min. From this azimuth angle dependence, the half-width Wh of the diffraction peak resulting from the oriented crystals in the width direction of the film was calculated. Furthermore, the degree of X-ray orientation was calculated using Wh according to the following formula: X-ray orientation degree = (180 - Wh) / 180

[0228] (11) Ratio of Unconstrained Amorphous Component (III) Determined by Pulse NMR The film was cut and packed into a glass tube having an outer diameter of 10 mm to a height of 1 cm. The spin-spin relaxation time T2 of the 1H nucleus of the biaxially oriented polypropylene film was measured using the following measuring device and measuring conditions to obtain a decay curve of the magnetization intensity. Apparatus: BRUKER Minispec mq20 Temperature: 40 ° C. Observation frequency: 20 MHz 90 ° pulse width: 2.74 μs Pulse repetition time: 2.0 s Pulse mode: Solid Echo method Number of accumulations: 128 times Recycle Delay: 4 s Acquisition Scale: 0.1 ms Measurement was started after placing a glass tube filled with biaxially oriented polypropylene film into the apparatus and keeping it warm for 15 minutes, and the component with the shortest relaxation time was separated by the least squares method using a Gaussian function, and the second and third shortest components were separated by the Lorentz function so that the decay curve of the obtained magnetization intensity and the fitting curve matched. The shortest component corresponds to the crystalline component (I), the second and third shortest components correspond to the constrained amorphous component (II), and the unconstrained amorphous component (III), respectively. FIG. 1 shows a schematic diagram of the attenuation curve and each curve obtained by waveform separation into the crystalline component (I), the amorphous component (II), and the unconstrained amorphous component (III). The fitting and analysis were performed using software (TD-NMR Analyzer) attached to the measurement device, in accordance with the product manual. The ratio of the unconstrained amorphous component (III) was calculated by the following formula (1), which is the ratio (%) of the amorphous component (III) to the total of the crystalline component (I), the constrained amorphous component (II), and the unconstrained amorphous component (III) obtained by the above method. Ratio of unconstrained amorphous component (III) = MIII / (M1 + MII + MIII) (1) M1: Amount of crystalline component (I) MII: Amount of constrained amorphous component (II) MIII: Amount of unconstrained amorphous component (III)

[0229] (12) Loop Stiffness Stress, Slope a of the Approximation Line The measurement method for the loop stiffness stress S (mN) in the width direction and the slope a of the approximation line of Equation (A) is as follows. Two 110 mm x 25.4 mm strips were cut out of the film, with the width direction of the strip as the long axis (loop direction). These were clamped between clips to create measurement loops, one with one side of the film forming the inner surface of the loop and the other with the opposite side forming the inner surface of the loop. The measurement loops were set in the chuck of a Loop Stiffness Tester DA manufactured by Toyo Seiki Co., Ltd., with the longitudinal direction perpendicular. The clips were then removed, and the loop stiffness stress was measured with a chuck spacing of 50 mm, an indentation depth of 15 mm, and a compression speed of 3.3 mm / sec. The loop stiffness stress and thickness were measured five times with one side of the film forming the inner surface of the loop, and then five times with the other side forming the inner surface of the loop. Using the data from these 10 runs, the cube of the thickness of each test piece was plotted on the horizontal axis and the loop stiffness stress on the vertical axis, and the least squares method was used to approximate a line with an intercept of 0, to determine the slope a. On the other hand, the slope a of the approximate line between the longitudinal loop stiffness stress S (mN) and formula (B) was measured in the same manner as the above measurement method, except that two measurement loops were cut out so that the long axes of the strips were in the longitudinal direction of the film, and the loops were set in a state where the width direction was perpendicular to the chuck portion.

[0230] (13) Wetting tension (mN / m) In accordance with JIS K 6768:1999, the film was aged for 24 hours at 23°C and 50% relative humidity, and then the corona-treated surface of the film was corona-treated to provide a release coating layer using the following procedure. Procedure 1) Measurement is performed in a standard laboratory atmosphere (see JIS K 7100) at a temperature of 23°C and a relative humidity of 50%. Procedure 2) The test piece is placed on the substrate of the hand coater (4.1), several drops of the test mixture are placed on the test piece, and immediately spread by pulling the wire bar. When using a cotton swab or brush to spread the test mixture, the liquid must be spread to at least 6 cm. ２The liquid should be spread quickly over an area of ​​at least 100 mm. The amount of liquid should be such that it forms a thin layer without forming puddles. The wetting tension is determined by observing the liquid film of the test mixed liquid in a bright place and observing the state of the liquid film after 3 seconds. If the liquid film does not break and remains in the same state as when it was applied for 3 seconds or more, it is considered to be wet. If the wetness remains for 3 seconds or more, proceed to a mixed liquid with the next higher surface tension. Conversely, if the liquid film breaks in 3 seconds or less, proceed to a mixed liquid with the next lowest surface tension. Repeat this process to select a mixed liquid that can accurately wet the surface of the test piece in 3 seconds.

[0231] (14) Evaluation of Releasability A release film was cut from a roll of biaxially oriented polypropylene film (hereinafter sometimes referred to as release film) coated with the silicone-based release agent described in the Examples to a width of 30 mm and a length of 80 mm, with the width direction being the long side, to serve as a sample for measuring peel force. After neutralization using a static eliminator (Keyence Corporation, SJ-F020), the film was 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. For the peel direction, double-sided adhesive tape (Nitto Denko Corporation, No. 535A) was attached to the SUS plate attached to the peel tester, and half of the release film was fixed thereon so that the release layer was adhered to the double-sided tape. The release film was then peeled by pulling the edge of the non-adhered side. Of the measured values ​​obtained, 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. The measurement was carried out five times in total, and the average value of the peel force was used for evaluation. The obtained peel force value was judged according to the following criteria: ○: 60 mN / mm or less. ×: More than 60 mN / mm. The peel angle in this evaluation method refers to the angle in the direction in which the release film is pulled relative to the axis of the evaluation sample fixed to the peel tester.

[0232] (15) Curl of Release Film A release film was cut into a size of 10 cm x 10 cm from a roll of biaxially oriented polypropylene film (release film) coated with the silicone-based release agent described in the Examples, and the release film sample was placed on a glass plate with the release side facing up, and the height of the part floating above the glass plate was measured. The curl that occurred in the release film was evaluated by the following method. 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.

[0233] (16) Wrinkles in Release Film Roll A biaxially oriented polypropylene film (hereinafter sometimes referred to as a release film) coated with the silicone-based release agent described in the Examples was unwound from a roll, and the wrinkles that occurred in the release film were evaluated by the following method. That is, a 60 cm wide release film was hung in a room at a temperature of 25°C and a humidity of 65% so that the film's longitudinal direction was vertical, 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, and 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 was 10 or less per meter. ×: The number of wrinkles is 11 or more per meter.

[0234] (Example 1) (Method of producing biaxially oriented polypropylene film) As the polypropylene resin, 80 parts by mass of propylene homopolymer PP-1 (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo Noblen FLX80E4) having MFR = 7.5 g / 10 min, [mmmm] = 98.9%, Tc = 116.2 ° C., Tm = 162.5 ° C., and 20 parts by mass of propylene homopolymer PP-2 (manufactured by Sumitomo Chemical Co., Ltd., EL80F5) having MFR = 11 g / 10 min, [mmmm] = 98.8%, Tc = 116.5 ° C., Tm = 161.5 ° C. were blended and used. The mixture was extruded into a sheet from a T-die at 250 ° C., brought into contact with a cooling roll at 20 ° C., and then placed in a water bath at 20 ° C. as is. The film was then stretched 4.5 times in the longitudinal direction using two pairs of rolls at 142°C, then both ends were clamped with clips and introduced into a hot air oven. After preheating at 170°C, it was stretched 10 times in the width direction at 162°C in the first stage. Immediately after stretching in the width direction, it was cooled at 120°C while still held by the clips, and then re-stretched 1.2 times in the width direction at 175°C, after which it was cooled to room temperature. One side of the film was corona-treated using a corona treater manufactured by Softal Corona & Plasma GmbH, and then wound up on a winder. The thickness of the film thus obtained was 18.6 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film-forming conditions. As shown in Table 3, the film had excellent rigidity and low thermal shrinkage at high temperatures, demonstrating excellent properties as a film for transfer substrates.

[0235] (Preparation of Biaxially Stretched Polypropylene Film Coated with Silicone-Based Release Agent) A coating liquid was applied to the corona-treated surface side of a roll of biaxially oriented polypropylene film for release. The coating liquid was a 50 / 50 toluene / methyl ethyl ketone solution (solid content concentration: 1% by mass) 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, at a coating amount (wet) of 3 g / m. ２ The release layer was then dried for 20 seconds using an air floating conveying type drying device with a distance between the upper and lower air flow outlets of 38 cm at a conveying tension of 2000 kPa and a drying temperature of 150°C, so that the mass of the release layer after drying and hardening was 0.03 g / m２ A release film of the formula (I) was obtained. 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. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film formation conditions. As shown in Table 3, the physical properties of the release film coated with the release agent were excellent in releasability, were smooth and wrinkle-free, and exhibited excellent properties as a film for a transfer substrate. The corona treatment was performed under the condition of an applied current value of 0.75 A.

[0236] (Example 2) The same procedure as in Example 1 was carried out, except that the film was re-stretched 1.2 times in the width direction at 165°C. The thickness of the obtained film was 18.4 µm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film-forming conditions. As shown in Table 3, the physical properties of the film were excellent in rigidity, had a low thermal shrinkage rate at high temperatures, and the release film coated with a release agent had excellent releasability and was a smooth, wrinkle-free film, demonstrating excellent properties as a film for a transfer substrate.

[0237] (Example 3) The same procedure as in Example 1 was carried out, except that the film was stretched in the longitudinal direction at 147°C, and then stretched 10 times in the width direction at 165°C as the first stage. Immediately after stretching in the width direction, it was cooled at 120°C while held by the clips, and then re-stretched 1.2 times in the width direction at 177°C. The thickness of the obtained film was 18.9 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film formation conditions. As shown in Table 3, the physical properties of the film were high rigidity and low heat shrinkage at high temperatures. The release film coated with a release agent had excellent releasability and was a smooth, wrinkle-free film, demonstrating excellent properties as a film for a transfer substrate.

[0238] (Example 4) The same procedure as in Example 3 was carried out, except that the film was re-stretched to 1.1 times the width direction at 177°C. The thickness of the obtained film was 20.6 µm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film-forming conditions. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film-forming conditions. As shown in Table 3, the physical properties of the film were high rigidity and low heat shrinkage at high temperatures, and the release film coated with a release agent had excellent releasability and was a smooth, wrinkle-free film, demonstrating excellent properties as a film for a transfer substrate.

[0239] Comparative Example 1 The same procedure as in Example 1 was carried out, except that the film was stretched 12 times in the width direction at 162°C as the first stage, and immediately after the width direction stretching, it was cooled at 100°C while held by the clips, and then heat-set at 170°C while maintaining a constant width. The thickness of the obtained film was 20.8 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film-forming conditions. As for the physical properties, as shown in Table 3, although the film had high rigidity, the thermal shrinkage rate at high temperatures was poor, and wrinkles occurred in the release film coated with a release agent, resulting in poor processability as a release film to be used for transfer.

[0240] (Comparative Example 2) The same procedure as in Example 1 was carried out, except that the film was stretched 12 times in the width direction at 162°C as the first stage, and immediately after the width direction stretching, it was heat-set at 172°C while the film was held by the clips without being cooled, while maintaining a constant width. The thickness of the obtained film was 23.1 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film-forming conditions. As shown in Table 3, the physical properties of the film were poor, such as poor rigidity, and wrinkles occurred in the release film coated with a release agent, resulting in poor processability as a release film for use in transfer.

[0241] (Comparative Example 3) The same procedure as in Example 1 was carried out, except that the film was stretched 12 times in the width direction at 168°C as the first stage, and immediately after the width direction stretching, it was cooled to 100°C while held by the clips, and then heat-set at 170°C while maintaining a constant width. The thickness of the obtained film was 18.7 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film-forming conditions. As shown in Table 3, the physical properties of the film were poor in rigidity, and wrinkles occurred in the release film coated with a release agent, resulting in poor processability as a release film to be used for transfer.

[0242] (Comparative Example 4) As the polypropylene resin, PP-3 (manufactured by Japan Polypropylene Corporation, FL203D) having MFR = 3 g / 10 min, [mmmm] = 94.8%, Tc = 117.2 ° C, Tm = 160.6 ° C was used. It was extruded into a sheet from a T-die at 250 ° C, brought into contact with a cooling roll at 20 ° C, and then placed directly into a water bath at 20 ° C. Thereafter, it was stretched 4.5 times in the longitudinal direction at 130 ° C., and in the width direction stretching with a tenter, the preheating temperature was set to 168 ° C., and 8.2 times stretching was performed at 155 ° C. as the first stage of stretching. Immediately after width direction stretching, it was cooled at 120 ° C. while held by the clip, and then re-stretched 1.2 times in the width direction at 170 ° C. Finally, it was cooled at room temperature. The thickness of the obtained film was 18.8 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film formation conditions. As shown in Table 3, the physical properties of the film were high in heat shrinkage at high temperatures and poor in rigidity. The film had poor releasability when coated with a release agent, and wrinkles occurred, making it unsuitable for processing as a release film for transfer.

[0243] (Comparative Example 5) Using a blend of PP-1 and PP-2 as the polypropylene resin in the same manner as in Example 1, a film was obtained under the film-forming conditions shown in Table 2, in which heat treatment was performed at 168°C without re-stretching in the width direction. The thickness of the obtained film was 20.0 µm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film-forming conditions. As for the physical properties, as shown in Table 3, the heat shrinkage rate at high temperatures was low, but the rigidity was poor, and wrinkles occurred in the release film coated with a release agent, resulting in poor processability as a release film to be used for transfer.

[0244] (Comparative Example 6) PP-4 (SA4L, manufactured by Japan Polypropylene Corporation) having an MFR of 5 g / 10 min, [mmmm] of 97.3%, Tc of 116.8°C, and Tm of 161.6°C was used as the polypropylene resin, and a film was obtained under the film-forming conditions shown in Table 2, in which the film was heat-treated at 168°C without being re-stretched in the width direction. The thickness of the obtained film was 20.0 μm. Table 1 shows the structure of the polypropylene resin, and Table 2 shows the film-forming conditions. As for the physical properties, as shown in Table 3, the heat shrinkage rate at high temperatures was low, but the rigidity was poor, and wrinkles occurred in the release film coated with a release agent, resulting in poor processability as a release film to be used for transfer.

[0245]

[0246]

[0247]

[0248] Furthermore, a transfer laminate was prepared using the film obtained in the examples, and transfer onto an article was performed. When a biaxially oriented polypropylene film without a release layer was used, the conditions of the corona treatment were adjusted.

[0249] (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 coating) obtained in Example 1, dried at 100°C, and then irradiated with ultraviolet light to form a 5 μm thick protective layer. 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. 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 flatness. The resulting roll of the laminate for transfer printing was unwound 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, transferring the protective layer / printing layer / adhesive layer. The contact time of the transfer roll was 3 seconds. During the transfer, the film and the protective layer were smoothly peeled off, the film contracted only slightly, and transfer printing was possible without transfer defects or misalignment.

[0250] (Metal Thin Film Layer Transfer) One side of the corona-treated biaxially oriented polypropylene film (without release coating) obtained in Example 1 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 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 designated position on the cardboard.

[0251] (Dry Film Resist) (Preparation of Biaxially Stretched Polypropylene Film Coated with Non-Silicone Release Agent) A coating liquid prepared by diluting a long-chain alkyl pendant compound (manufactured by Chukyo Yushi Co., Ltd., product name: Resem P-677) with a water / isopropyl alcohol mixed solvent was applied to the corona-treated surface side of the roll-shaped biaxially oriented polypropylene film for release obtained in Example 2, 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 between the upper and lower air flow outlets of 38 cm, so that the mass of the release layer after drying and hardening was 0.03 g / m ２A release film of the formula (I) was obtained. 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 following photosensitive resin solution, obtained with reference to the examples in JP 2006-114735 A, was applied to the release surface of the biaxially oriented polypropylene film provided with the non-silicone release layer, and the solvent was removed to provide a photosensitive resin layer of 30 μm in thickness. A biaxially oriented polypropylene film provided with the silicone-based release layer of Example 2 was laminated as a protective film to the surface of the photosensitive resin layer opposite the substrate, to obtain a photosensitive resin laminate. The obtained photosensitive resin laminate was free from warping and had excellent 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 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: 88 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

[0252] The protective film was peeled off from the resulting photosensitive resin laminate, and the copper foil surface of the copper-clad film on the exposure device was pressed against the photosensitive resin layer surface. A negative was then placed on the substrate film surface and the pressure was reduced to allow for close contact. After exposure from the negative side, the substrate 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.

[0253] (Retardation layer) An aqueous solution of fully saponified polyvinyl alcohol was applied to one side of the corona-treated biaxially stretched polypropylene film (without release coating) obtained in Example 3, and dried in an oven at 110°C for 40 seconds to form a film with a thickness of 200 nm. Subsequently, the surface of the obtained film was treated with a rubbing roll wrapped with a nylon napped cloth. Rubbing was performed at an angle of 45° to the MD direction of the substrate film.

[0254] Subsequently, a solution for forming a retardation layer (liquid crystal compound alignment layer) having the following composition was applied to the rubbed surface by a bar coating method. Rod-shaped liquid crystal compound (LC242 manufactured by BASF) 24.15 parts by mass Surfactant (Ftergent FTX-209F manufactured by Neos) 0.12 parts by mass Reaction initiator (IRGACURE379 manufactured by BASF) 0.73 parts by mass Solvent (cyclopentyl methyl ether) 75.00 parts by mass The film was dried in an oven at 125 ° C. for 5 minutes to align the liquid crystals, and then irradiated with ultraviolet light while maintaining the liquid crystal alignment to harden the liquid crystal compound, and a λ / 4 layer was provided as a retardation layer, thereby obtaining a laminate for transferring the retardation layer. A UV-curable adhesive was applied to a rectangular commercially available polarizing plate, and the retardation layer surface of the obtained retardation layer transfer laminate was attached to the biaxially oriented polypropylene film so that the MD direction was parallel to the long side of the polarizing plate. After irradiating with UV light to cure the adhesive, the film was peeled off. When the orientation direction of the retardation layer was measured, it was found to be 45 degrees to the long side of the polarizing plate as expected, and a circular polarizing plate was obtained.

[0255] (Circuit) A 10 μm thick copper foil was bonded to the release layer surface of the biaxially oriented polypropylene film provided with the silicone-based release layer obtained in Example 1 using an EVA-based hot melt adhesive. A resist loop antenna pattern was then printed on the copper foil by screen printing, the resist was cured, and the exposed copper foil was removed by etching. After removing the resist, an adhesive was applied to obtain a circuit transfer laminate. The adhesive layer surface of the circuit transfer laminate was placed on a resin molded body, and a silicone pad heated to 150° C. was pressed against the film surface for 5 seconds, after which the substrate film was peeled off. A molded body having the loop antenna circuit as designed was obtained.

[0256] (Adhesive) Referring to Example 1 of JP 2009-286883 A, 40 parts by weight of crystalline aliphatic polyester diol (Sun-Ester 4620 manufactured by Sanyo Chemical Industries, Ltd.), 60 parts by weight of polypropylene glycog, 10 parts by weight of rosin ester (Pine Crystal KE-311 manufactured by Arakawa Chemical Industries, Ltd.), and 25.2 parts by weight of 4,4'-diphenylmethane diisocyanate were reacted, and then 0.1 parts by weight of 2,2'-dimorpholinodiethyl ether (U-CAT 660M manufactured by San-Apro Co., Ltd.) was added to obtain a reactive hot melt adhesive. The resulting reactive hot melt adhesive was melted at 130°C and spread using a slit die onto the release layer of the biaxially oriented polypropylene film provided with the silicone-based release layer obtained in Example 4 to form a 25 μm thick adhesive layer, which was then cooled and wound up. The wound reactive hot melt adhesive transfer laminate was packaged in aluminum-vapor-deposited polyester film together with a desiccant. The resulting reactive hot melt adhesive transfer laminate was wrinkle-free and had excellent flatness. The reactive hot melt adhesive transfer laminate was unwound, and the adhesive layer side of the laminate was placed on the MDF board side. The MDF board and adhesive layer side were bonded together using a roll heated to 150 ° C. from the substrate film side. The contact time with the heated roll was 3 seconds. After that, the substrate film was peeled off, and a cotton and nylon blended fabric was placed on the adhesive layer side, and the fabric was bonded to the MDF board using a roll heated to 150 ° C.

[0257] (Optical Pressure-Sensitive Adhesive) An acrylic pressure-sensitive adhesive was obtained by the following method with reference to WO 2012 / 029471. 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 were added per 100 parts of solids, and the mixture was diluted with ethyl acetate to obtain a pressure-sensitive adhesive solution with a solids concentration of 12%. The above-mentioned non-silicone release agent was applied to the corona-treated biaxially oriented polypropylene film obtained in Example 4 to form a release layer, and an acrylic pressure-sensitive adhesive solution was applied to the release layer surface of the obtained release film, dried at 130°C for 5 minutes, and subjected to a crosslinking reaction to form a 17 μm-thick pressure-sensitive adhesive layer. The biaxially oriented polypropylene film provided with the silicone release agent obtained in Example 1 was then bonded to the pressure-sensitive adhesive layer surface and wound up. An optical pressure-sensitive adhesive transfer laminate with little shrinkage and excellent flatness was obtained. 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 from the optical pressure-sensitive adhesive transfer laminate, the adhesive layer surface was bonded to a polarizing plate. The substrate film surface was then peeled off and bonded to a glass plate simulating a liquid crystal cell. The substrate film had a moderate stiffness, allowing for smooth peeling, and no peeling marks were observed on the adhesive layer.

[0258] As described above, the biaxially oriented polypropylene films for transfer substrates of the examples could be used for transfer in a variety of applications. On the other hand, as can be seen from the evaluation of wrinkles on the biaxially oriented polypropylene film coated with a silicone-based release agent, the biaxially oriented polypropylene film of the comparative example is prone to wrinkles and deterioration of flatness due to heat in the drying process, etc., which limits its applications. The evaluation of wrinkles and flatness was performed by placing the processed film or transfer laminate with the film face up on a table and looking at the reflected fluorescent light on the ceiling to evaluate the distortion of the film surface. Long distortions with a width of about 1 cm or less were considered wrinkles, while wide distortions, convex or concave distortions, and full-scale wavy distortions were considered to have poor flatness.

[0259] (Examples of the Second Disclosure) As described above, the biaxially oriented polypropylene films of Examples 1 to 4 had high rigidity and low heat shrinkage at high temperatures. Furthermore, the biaxially oriented polypropylene films (release films) coated with a release agent had excellent releasability and were smooth and wrinkle-free. Therefore, they had excellent properties as films for use in thin film manufacturing processes. On the other hand, as described above, the biaxially oriented polypropylene films of Comparative Examples 1 to 6 had low rigidity or high heat shrinkage at high temperatures. Furthermore, the release films coated with a release agent wrinkled, so they were poorly processable as films for use in thin film manufacturing processes.

[0260] Furthermore, the following thin films were produced using the biaxially oriented polypropylene films obtained in Examples 1 to 4. When using biaxially oriented polypropylene films without a release layer, the conditions of the corona treatment were adjusted.

[0261] (Thermosetting resin film) The following phenoxy resin solution was coated on the release layer surface of the biaxially oriented polypropylene film having a silicone-based release layer obtained in Example 1 so that the thickness of the resin film after drying would be 5 μm, and 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 produce a laminated film. Polyvinyl butyral (Sekisui Chemical Co., Ltd., "S-LEC (registered trademark) B BL-10") 9.9 parts by mass Epoxy resin A: bisphenol A type epoxy resin (DIC Corporation, "EPICLON (registered trademark) EXA-4850-1000") 37.9 parts by mass Epoxy resin B: dicyclopentadiene type epoxy resin (DIC Corporation, "EPICLON (registered trademark) HP-7200") 24.7 parts by mass Heat curing agent: novolac type phenolic resin (Showa Denko K.K., "SHONOL (registered trademark) BRG-556") 18.3 parts by mass Curing accelerator: 2-phenyl-4,5-dihydroxymethylimidazole (Shikoku Chemicals Corporation, "Curesol (registered trademark) 2PHZ") 0.2 parts by mass Filler: spherical silica (Admatechs Co., Ltd., "Admanano (registered trademark) YA050C-MKK") 9.0 parts by mass; BYK-370 (by BYK Japan, silicone surfactant) 0.4 parts by mass; Solvent: methyl ethyl ketone 100 parts by mass. Then, the biaxially oriented polypropylene film having the release layer was peeled off from the laminate to obtain a thermosetting resin film. The obtained thermosetting resin film was free of wrinkles, had good flatness, and had an excellent appearance.

[0262] (Aromatic Polyamide Film) 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 with reference to Example 1 of JP 2015-168194 A. The resulting aromatic polyamide solution was applied to the corona-treated biaxially oriented polypropylene film (without release coating) obtained in Example 3, heated at 150°C for 60 seconds to evaporate the solvent, and then the biaxially oriented polypropylene film was peeled off. The resulting aromatic polyamide film was introduced into a water bath and subjected to an extraction process. 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 aromatic polyamide film was wrinkle-free, had good flatness, and had an excellent appearance.

[0263] (Polymer electrolyte film) (Preparation of biaxially oriented polypropylene film coated with non-silicone-based release agent) A coating liquid prepared by diluting a long-chain alkyl pendant compound (manufactured by Chukyo Yushi Co., Ltd., product name: Resem P-677) with a water / isopropyl alcohol mixed solvent was applied to the corona-treated surface side of the roll-shaped biaxially oriented polypropylene film for release obtained in Example 2, 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 flotation conveying type drying device with a distance between the upper and lower air flow outlets of 38 cm, so that the mass 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 / second using a cooling roll at 50°C, and then taken up into a roll to obtain a release film roll.

[0264] Referring to Japanese Patent Application Laid-Open No. 2008-181856, 3,3'-disulfo-4,4'-dichlorodiphenyl sulfone disodium salt, 2,6-dichlorobenzonitrile, 4,4'-biphenol, and potassium carbonate were reacted in N-methyl-2-pyrrolidone to obtain an N-methyl-2-pyrrolidone solution of an ionic group-containing resin (solids concentration: 20% by mass). The resulting solution was applied to the release layer surface of a biaxially oriented polypropylene film coated with the non-silicone release agent described above, dried at 130°C for 10 minutes, 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. The release film was then peeled off to obtain a polymer electrolyte membrane with a thickness of 18 μm. The resulting polymer electrolyte membrane was wrinkle-free, had good flatness, and had an excellent appearance.

[0265] (Porous film) A resin solution was prepared by mixing and dissolving 100 parts by weight of a polyamideimide solution [manufactured by Toyobo Co., Ltd., trade name "Viromax HR11NN"], 30 parts by weight of polyvinylpyrrolidone (molecular weight 55,000), and a silicone surfactant. This resin solution was applied to the release layer surface of the biaxially stretched polypropylene film coated with the silicone release agent of Example 4. After that, it was kept 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. After that, the release film was peeled off to obtain a porous film. The obtained porous film was wrinkle-free, had good flatness, and had an excellent appearance.

[0266] As described above, the biaxially oriented polypropylene films of the Examples could be used as process films when producing various thin films. On the other hand, the biaxially oriented polypropylene films of the Comparative Examples, as can be seen from the evaluation of wrinkles on the biaxially oriented polypropylene films coated with a silicone-based release agent, are subject to limitations due to the tendency for wrinkles and deterioration of flatness due to heat in the drying process, etc. The evaluation of wrinkles and flatness of the thin film was performed by placing a laminate of the biaxially oriented polypropylene film and a thin film immediately before peeling the thin film on a table with the film facing up, and looking at the reflected fluorescent light on the ceiling to evaluate the distortion of the film surface. Long distortions with a width of about 1 cm or less were considered wrinkles, while wide distortions, convex or concave distortions, and full-scale wavy distortions were considered to have poor flatness.

[0267] The biaxially oriented polypropylene film for transfer substrates according to the first disclosure has excellent heat resistance and rigidity, and therefore, the occurrence of wrinkles and deterioration of flatness are suppressed when forming a transfer layer or during heat treatment. Furthermore, the film is easy to peel even when thinned, and can be suitably used as a film for transfer substrates for various applications.

[0268] The biaxially oriented polypropylene film for thin film manufacturing processes of the second disclosure has excellent heat resistance and rigidity, so that the occurrence of wrinkles and deterioration of flatness are suppressed during thin film formation and heat treatment. Furthermore, even when the film is thinned, it is easy to peel, and it can be suitably used as a film for various types of thin film manufacturing processes.

Claims

1. A biaxially oriented polypropylene film for transfer substrates or thin film manufacturing processes, which satisfies the following (1), (2), and (3): (1) The mesopentad fraction of the polypropylene resin constituting the biaxially oriented polypropylene film is 97.5% or more. (2) The relationship between the loop stiffness stress S [mN] in the width direction and the thickness t (μm) satisfies the following formula (A): S≧0.0010×t ３ ...(A) (3) When separated into a crystalline component (I), a constrained amorphous component (II), and an unconstrained amorphous component (III) as determined by pulse NMR using the solid echo method, the ratio of (III) is 7% or less.

2. The biaxially oriented polypropylene film according to claim 1, wherein the heat shrinkage rate of the biaxially oriented polypropylene film at 150°C is 10% or less in the longitudinal direction and 25% or less in the transverse direction.

3. The biaxially oriented polypropylene film according to claim 1, wherein the refractive index Ny in the width direction of the biaxially oriented polypropylene film is 1.5250 or more and ΔNy is 0.0240 or more.

4. The biaxially oriented polypropylene film according to claim 1, wherein the haze of the biaxially oriented polypropylene film is 5.0% or less.

5. The biaxially oriented polypropylene film according to claim 1, in which the half-width of the peak derived from oriented crystals in the width direction in the azimuth angle dependence of the (110) plane of polypropylene α-type crystals obtained by wide-angle X-ray diffraction measurement is 30° or less.

6. The biaxially oriented polypropylene film according to claim 1, wherein the polypropylene resin has a crystallization temperature of 105°C or higher and a melting point of 160°C or higher.

7. The biaxially oriented polypropylene film according to claim 1, wherein the polypropylene resin has a melt flow rate of 4.0 g / 10 min or more.

8. A biaxially oriented polypropylene film as described in claim 1, in which the amount of components with a molecular weight of 100,000 or less in the polypropylene resin is 35 mass% or more.

9. A release layer-laminated polypropylene film for transfer, comprising the biaxially oriented polypropylene film for transfer substrate according to any one of claims 1 to 8 and a release layer laminated on at least one surface of the biaxially oriented polypropylene film for transfer substrate.

10. A transfer laminate film comprising the biaxially oriented polypropylene film for transfer substrates according to any one of claims 1 to 8 and a transfer layer.

11. The transfer laminate film according to claim 10, wherein the transfer layer comprises at least one layer selected from the group consisting of 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, and a rubber sheet layer.

12. A transfer method comprising the steps of: bonding the transfer laminate film described in claim 10 to an object to be transferred; and peeling off the biaxially oriented polypropylene film for transfer substrate of the transfer laminate film from the object to which the transfer laminate film is bonded.

13. The transfer method according to claim 12, wherein the object is any one of paper, film, cloth, wood, glass, ceramics, metal, a resin molded product, and a conductive thin film laminate.

14. A release layer-laminated biaxially oriented polypropylene film for thin film manufacturing processes, comprising a biaxially oriented polypropylene film for thin film manufacturing processes according to any one of claims 1 to 8 and a release layer laminated on at least one side of the biaxially oriented polypropylene film for thin film manufacturing processes.

15. A method for producing a thin film, comprising step 1A of preparing a biaxially oriented polypropylene film for a thin film production process according to any one of claims 1 to 8, step 1B of providing a thin film layer on at least one surface of the biaxially oriented polypropylene film for a thin film production process, and step 1C of peeling the thin film layer from the biaxially oriented polypropylene film for a thin film production process.

16. The method for producing a thin film according to claim 15, wherein the thin film layer includes any one of a resin film, a polymer electrolyte membrane, and a porous membrane.

17. A method for producing a thin film, comprising step 2A of preparing a release layer-laminated biaxially oriented polypropylene film for use in a thin film manufacturing process as described in claim 14, step 2B of providing a thin film layer on the release layer surface of the release layer-laminated biaxially oriented polypropylene film for use in a thin film manufacturing process, and step 2C of peeling the thin film layer from the release layer.

18. The method for producing a thin film according to claim 17, wherein the thin film layer includes any one of a resin film, a polymer electrolyte membrane, and a porous membrane.