Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
  • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
  • B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
  • B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
  • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
  • B32B7/04—Interconnection of layers
  • B32B7/06—Interconnection of layers permitting easy separation
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J7/00—Chemical treatment or coating of shaped articles made of macromolecular substances
  • C08J7/04—Coating
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
  • C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2067/00—Use of polyesters or derivatives thereof, as moulding material
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
  • C08J2367/04—Polyesters derived from hydroxy carboxylic acids, e.g. lactones

Definitions

• the present invention relates to a polylactic acid film made of a resin composition containing polylactic acid, and a laminate film containing the same.
• PLA polylactic acid
• Polylactic acid resin are derived from biomass raw materials and are biodegradable, so they are being developed as an alternative to conventional fossil raw materials.
• polylactic acid films made from polylactic acid resin have a low elastic modulus and low heat resistance. For this reason, when used for industrial purposes, PLA films have problems such as dimensional changes during processing and appearance defects such as wrinkles.
• Patent Document 1 discloses a manufacturing method in which the longitudinal stretching is divided into two or more steps, followed by widthwise stretching, with the second longitudinal stretching performed at a temperature lower than the first stretching temperature, thereby improving heat resistance without impairing formability.
• the polylactic acid film produced by the method of Patent Document 1 has improved heat resistance, the second longitudinal stretching temperature is low, so the subsequent widthwise stretching ratio cannot be set high, and the film has the problem of low elastic modulus.
• An object of the present invention is to provide a polylactic acid film having excellent elastic modulus and heat resistance, which is produced by using polylactic acid derived from a biomass raw material and has biodegradability, and a laminate film containing the same.
• the present invention has the following configuration.
• a polylactic acid film made of a resin composition containing polylactic acid A polylactic acid film having a longitudinal tensile modulus Ea and a transverse tensile modulus Eb that satisfy the formula Ea + Eb > 8.0 GPa, a crystallinity of 40% or more and 90% or less, and a longitudinal heat shrinkage rate and a transverse heat shrinkage rate each of which are 10.0% or less when heated at 150°C for 30 minutes.
• the polylactic acid film according to any one of 1. to 3. above which has a total light transmittance of 75% or more and a haze of 3% or less.
• the laminated film according to the above item 5 which is a release film for use in producing a ceramic green sheet, and the release layer is made of a composition containing a silicone release component.
• the laminate film according to 5. or 6. above wherein the maximum projection height (P) of the surface of the release layer is 200 nm or less, and the arithmetic mean roughness (Sa) of the surface of the release layer is 10 nm or less.
• the polylactic acid film of the present invention has excellent elastic modulus and heat resistance. Therefore, it has good dimensional stability during processing at high temperatures and high rigidity, making it suitable for industrial applications such as release film and optical applications. Furthermore, since it is made from biomass-derived raw materials and is biodegradable, it is possible to provide excellent polylactic acid films and laminated films containing the same that take into consideration the recent SDGs.
• the polylactic acid film of the present invention is a polylactic acid film made of a resin composition containing polylactic acid.
• the longitudinal tensile modulus Ea and the transverse tensile modulus Eb satisfy the formula "Ea + Eb > 8.0 GPa", the crystallinity is 40% to 90%, and when heated at 150°C for 30 minutes, the longitudinal heat shrinkage rate and the transverse heat shrinkage rate are each 10.0% or less.
• the laminated film of the present invention is a laminated film containing this polylactic acid film, and is preferably a laminated film containing a polylactic acid film in a substrate layer and further having a release layer on one or both surfaces of the substrate layer.
• the polylactic acid preferably used in the present invention is obtained by ring-opening polymerization of lactide using a compound having a hydroxyl group as an initiator in the presence of a specific catalyst.
• the specific catalyst is, for example, tin, aluminum, etc.
• the polylactic acid can contain an L-lactic acid component and a D-lactic acid component as a copolymer component or a blend component.
• the weight ratio of L-lactic acid (hereinafter L-form)/D-lactic acid (hereinafter D-form) is preferably 100/0 to 85/15, more preferably 100/0 to 90/10, even more preferably 100/0 to 90/10, and particularly preferably 100/0 to 95/5.
• L-form L-lactic acid
• D-form D-lactic acid
• the preferred glass transition point is 40 to 70°C
• the preferred melting point is 150 to 180°C
• it is also preferable that oriented crystallization is possible.
• the glass transition point and melting point can be measured by a differential scanning calorimeter (DSC), etc.
• DSC differential scanning calorimeter
• the reduced viscosity ( ⁇ sp/c) of the resin composition used in the present invention is preferably in the range of 1.0 dl/g or more and 3.0 dl/g or less.
• ⁇ sp/c The reduced viscosity ( ⁇ sp/c) of the resin composition used in the present invention is preferably in the range of 1.0 dl/g or more and 3.0 dl/g or less.
• the reduced viscosity is 1.0 dl/g or more, tearing of the polylactic acid film can be prevented.
• the reduced viscosity is 3.0 dl/g or less, the increase in filtration pressure is small, making high-precision filtration easier.
• the reduced viscosity ( ⁇ sp/c) of the polylactic acid film of the present invention is preferably in the range of 1.0 dl/g or more and 2.5 dl/g or less.
• the reduced viscosity is 1.0 dl/g or more, it is preferable because not many breaks occur during the stretching process.
• the reduced viscosity is 2.5 dl/g or less, it is preferable because the cuttability is good when cutting to a specified product width and dimensional defects do not occur.
• the resin composition used in the present invention may contain one or more of various additives, such as inert particles such as inorganic particles, heat-resistant polymer particles, and crosslinked polymer particles, fluorescent brighteners, ultraviolet protection agents, infrared absorbing dyes, heat stabilizers, surfactants, and antioxidants, depending on the purpose of use.
• additives such as inert particles such as inorganic particles, heat-resistant polymer particles, and crosslinked polymer particles, fluorescent brighteners, ultraviolet protection agents, infrared absorbing dyes, heat stabilizers, surfactants, and antioxidants, depending on the purpose of use.
• aromatic amine-based and phenol-based antioxidants can be used.
• phosphorus-based stabilizers such as phosphoric acid and phosphate ester-based, sulfur-based, and amine-based stabilizers can be used.
• the polylactic acid film of the present invention is preferably an oriented film, more preferably a biaxially oriented film, from the standpoints of mechanical strength, chemical resistance, heat resistance, and the like.
• the resin composition of the present invention can be processed into an unstretched sheet by various methods, and then biaxially stretched to obtain a polylactic acid film.
• the melt extrusion method can be used to manufacture the unstretched sheet.
• the melt extrusion method is preferred in the present invention.
• the melting temperature of the resin composition is preferably in the range of 150 to 250°C, and more preferably 180 to 240°C.
• a temperature of 150°C or higher is preferable because it provides an appropriate melt viscosity and increases productivity.
• a temperature of 250°C or lower is preferable because it suppresses thermal degradation of the polylactic acid resin.
• the die temperature during melt extrusion is the same as above, but is preferably 150 to 300°C, more preferably 170 to 290°C, and even more preferably 180 to 240°C.
• the die temperature during melt extrusion is 150°C or higher, the melt viscosity falls into an appropriate range and stable extrusion is possible.
• the temperature is 300°C or lower, thermal decomposition of the resin can be suppressed.
• the polylactic acid film of the present invention can be manufactured according to a general polyester film manufacturing method.
• a method can be used in which a polyester resin is melted, extruded into a sheet, and the unoriented polyester is stretched in the longitudinal direction at a temperature equal to or higher than the glass transition temperature by utilizing the speed difference between rolls, and then stretched in the transverse direction by a tenter and heat-treated.
• the film is heated and stretched 1.1 to 6 times between two or many rolls with different peripheral speeds.
• the heating means at this time may be a method using a heated roll or a method using a non-contact heating medium, or these may be used in combination.
• the temperature of the film in the range of (Tg-10°C) to (Tg+50°C).
• a heat setting process within 30 seconds, preferably within 10 seconds, and to carry out a longitudinal relaxation process and a transverse relaxation process of 0.5 to 10%.
• the heat setting temperature is preferably in the range of 90 to 180°C. Heat setting temperatures of 90°C or higher are preferred because they provide sufficient thermal dimensional stability for the film. Heat setting temperatures of 180°C or lower are preferred because they prevent holes from forming in the film due to heat.
• the thickness of the polylactic acid film of the present invention is preferably 2 ⁇ m or more and 500 ⁇ m or less, more preferably 15 ⁇ m or more and 400 ⁇ m or less, and even more preferably 20 ⁇ m or more and 250 ⁇ m or less.
• the thickness of the polylactic acid film is 2 ⁇ m or more, the polylactic acid film has a minimum rigidity and is easy to handle.
• the thickness of the polylactic acid film is 500 ⁇ m or less, the transportability of the film when transporting the film with multiple rolls and the handleability of the produced film are improved, making it easy to handle.
• the sum of the tensile modulus Ea in the MD direction and the tensile modulus Eb in the TD direction of the polylactic acid film is preferably 8.0 GPa or more.
• the preferred lower limit of the sum of the tensile modulus is 8.2 GPa, more preferably 8.4 GPa, even more preferably 8.6 GPa, even more preferably 8.8 GPa, even more preferably 9.0 GPa, particularly preferably 9.5 GPa, and most preferably 10.0 GPa or more.
• a sum of the tensile modulus of elasticity of 8.0 GPa or more is preferable because the film has sufficient rigidity and wrinkles and warping of the film can be suppressed.
• the upper limit of the sum of the tensile modulus of elasticity is considered to be 15.0 GPa.
• the breaking strength of the polylactic acid film is preferably 75 MPa or more in both the MD and TD directions.
• the preferred lower limit of the breaking strength is 100 MPa, more preferably 150 MPa, even more preferably 200 MPa, and even more preferably 220 MPa.
• a breaking strength of 75 MPa or more is preferable because the mechanical strength of the film is sufficient and the occurrence of problems such as elongation and displacement during the film processing process can be suppressed. Taking manufacturing considerations into account, the upper limit of the breaking strength is considered to be 1000 MPa.
• the breaking elongation of the polylactic acid film is preferably 5% or more in both the MD and TD directions.
• a breaking elongation of 5% or more is preferable because the mechanical elongation of the film is sufficient, and the occurrence of defects such as cracking and tearing during the film processing process can be suppressed.
• the upper limit of the breaking elongation is thought to be 300%.
• the upper limit of the breaking elongation is more preferably 150%, even more preferably 100%, and even more preferably 80%.
• the heat shrinkage rate in the MD direction and the heat shrinkage rate in the TD direction are each 10.0% or less.
• the upper limits of the heat shrinkage rate in the MD direction and the heat shrinkage rate in the TD direction are more preferably 8.0% or less, even more preferably 6.0% or less, even more preferably 4.0% or less, particularly preferably 3.0% or less, and most preferably 2.0% or less.
• a small heat shrinkage rate makes it easier to carry out processing such as coating, and can suppress poor appearance due to deformation of the film under high heat. It is preferable that the heat shrinkage rate is low, but from a manufacturing standpoint, 0.01% is considered to be the lower limit.
• the heat shrinkage rate in the MD direction and the heat shrinkage rate in the TD direction are each 3.0% or less.
• the upper limits of the heat shrinkage rate in the MD direction and the heat shrinkage rate in the TD direction are more preferably 2.0% or less, even more preferably 1.6% or less, even more preferably 1.4% or less, particularly preferably 1.2% or less, and most preferably 1.0% or less.
• a small heat shrinkage rate makes it easier to carry out processing such as coating, and can suppress poor appearance due to deformation of the film under high heat. It is preferable that the heat shrinkage rate is low, but from a manufacturing standpoint, 0.01% is considered to be the lower limit.
• the total light transmittance of the polylactic acid film is preferably 75% or more.
• the total light transmittance of the film of the present invention is preferably 75% or more, more preferably 80% or more, even more preferably 85% or more, even more preferably 88% or more, particularly preferably 91% or more, and most preferably 93% or more.
• the higher the total light transmittance the better, but it is technically difficult to achieve a total light transmittance of 100%. From a manufacturing standpoint, it is preferable that the total light transmittance is less than 100%.
• the surface of the polylactic acid film of the present invention is preferably smooth, and when used as a release film for producing ceramic green sheets, it is preferable that the haze is small.
• the haze is preferably 3% or less, more preferably 2% or less, and most preferably 1% or less.
• the lower limit of the haze is the lower the better, but it can be 0.1% or more, or even 0.3% or more. From the perspective of reducing the haze, it is better not to have too much unevenness on the film surface, but from the perspective of handling ease with respect to a rotating roll, it is preferable to form a certain amount of unevenness on at least one surface to provide a certain degree of slipperiness.
• the crystallinity of the polylactic acid film is preferably 40% to 90%. It is more preferable that it is 50% to 85%, and even more preferable that it is 55% to 80%. A crystallinity in the range of 40% to 90% is preferable because it improves strength and provides a high elastic modulus.
• a smooth release layer or the like is formed on the surface of a polylactic acid film
• at least one surface of the polylactic acid film is also smooth.
• the smooth surface of the polylactic acid film it is preferable that the arithmetic mean roughness (Sa) is 10 nm or less and the maximum protrusion height (P) is 200 nm or less.
• the arithmetic mean roughness of the surface is 10 nm or less and the maximum protrusion height is 150 nm or less, and it is even more preferable that the arithmetic mean roughness of the surface is 10 nm or less and the maximum protrusion height is 120 nm or less, and it is even more preferable that the arithmetic mean roughness of the surface is 8 nm or less and the maximum protrusion height is 120 nm or less. If the arithmetic mean roughness of the surface is 10 nm or less and the maximum protrusion height is 200 nm or less, the surface of the release layer or the like formed on the surface can be smoothed to the same degree.
• the arithmetic mean roughness (Sa) of the surface of the polylactic acid film may be 0.1 nm or more, or may be 0.3 nm or more. Additionally, the maximum protrusion height (P) on the surface can be 1 nm or more, or 3 nm or more.
• the laminated film of the present invention is a laminated film having a base layer and a release layer, the base layer containing the polylactic acid film as described above.
• the release layer can be provided on one or both sides of the base layer, and is preferably provided on the outermost surface.
• the substrate layer may be made of a polylactic acid film, but may further include other layers such as other polyester layers, an easy-adhesion layer, an antistatic layer, and an easy-slip layer.
• the laminated film of the present invention can be used for the production or transfer of ceramic green sheets, various resin sheets, and optical films, and as a release film for pressure sensitive adhesive sheets, adhesive sheets, and the like.
• the resin constituting the release layer is not particularly limited, and may be a silicone resin, a fluororesin, an alkyd resin, various waxes, an aliphatic olefin, etc., and each resin may be used alone or in combination of two or more kinds.
• the release layer preferably contains a silicone release component such as a silicone resin or a silicone oil.
• silicone resin is a resin that has a silicone structure in the molecule, and examples include cured silicone, silicone graft resin, and modified silicone resin such as alkyl modified, but from the viewpoint of migration, it is preferable to use reactive cured silicone resin.
• reactive cured silicone resins that can be used include addition reaction type, condensation reaction type, and ultraviolet or electron beam cured type. More preferably, low-temperature curing addition reaction type that can be processed at low temperature, and ultraviolet or electron beam cured type are good.
• An example of an addition reaction silicone resin is one in which polydimethylsiloxane with vinyl groups at the end or side chain is reacted with hydrogen siloxane using a platinum catalyst to harden it.
• a resin that can harden within 30 seconds at 120°C, as this allows processing at low temperatures.
• Examples include low-temperature addition cure types (LTC1006L, LTC1056L, LTC300B, LTC303E, LTC310, LTC314, LTC350G, LTC450A, LTC371G, LTC750A, LTC755, LTC760A, etc.) and thermal UV cure types (LTC851, BY24-510, BY24-561, BY24-562, etc.) manufactured by Dow Toray, and solvent addition + UV cure types (X62-5040, X62-5065, X62-5072T, KS5508, etc.) and dual cure types (X62-2835, X62-2834, X62-1980, etc.) manufactured by Shin-Etsu Chemical Co., Ltd.
• low-temperature addition cure types LTC1006L, LTC1056L, LTC300B, LTC303E, LTC310, LTC314, LTC350G, LTC450A, LTC371G, LTC750A, LTC755, LTC760A, etc
• An example of a silicone resin that uses a condensation reaction is one that creates a three-dimensional crosslinked structure by condensing polydimethylsiloxane with terminal OH groups and polydimethylsiloxane with terminal H groups using an organotin catalyst.
• UV-curing silicone resins include the most basic type, which uses the same radical reaction as normal silicone rubber crosslinking, those which introduce unsaturated groups and are photocured, those which use UV light to decompose onium salts to generate strong acids which then cleave epoxy groups to cause crosslinking, and those which crosslink by an addition reaction of thiols to vinyl siloxanes. Electron beams can also be used instead of UV light. Electron beams have more energy than UV light, and it is possible to carry out a radical crosslinking reaction without using an initiator as in the case of UV curing. Examples of resins that can be used include UV-curable silicones manufactured by Shin-Etsu Chemical Co., Ltd.
• UV-curable silicones manufactured by Momentive Performance Materials Inc. TPR6502, TPR6501, TPR6500, UV9300, UV9315, XS56-A2982, UV9430, etc.
• UV-curable silicones manufactured by Arakawa Chemical Co., Ltd. Silicolease UV POLY200, POLY215, POLY201, KF-UV265AM, etc.
• Acrylate-modified or glycidoxy-modified polydimethylsiloxane can also be used as the UV-curable silicone resin. Good release performance can also be achieved by mixing these modified polydimethylsiloxanes with multifunctional acrylate resins or epoxy resins and using them in the presence of an initiator.
• resins that can be used include alkyd resins and acrylic resins with long-chain alkyl groups, such as stearyl- or lauryl-modified resins, or alkyd-based resins, acrylic-based resins, and olefin-based resins obtained by reactions such as methylated melamine.
• release agents that do not contain silicone are also preferred.
• Examples of the amino alkyd resins and amino acrylic resins obtained by the above-mentioned reaction of methylated melamine include the Tesfine series manufactured by Showa Denko Materials Co., Ltd.
• one type may be used, or two or more types may be mixed.
• two or more types may be mixed, two or more types of silicone-based resins may be used, and it is also preferable to mix multiple different resin types, such as a binder resin and a silicone-based resin.
• the release layer does not deform when peeled off, so it is preferable that the release layer is crosslinked and hardened. Therefore, it is also preferable that the release layer contains a binder component and a crosslinking agent in addition to the silicone-based release agent.
• the binder component contained in the release layer of the present invention is preferably, for example, a component that can be crosslinked to increase the crosslink density of the release layer and improve the durability and solvent resistance of the release layer. Therefore, the binder component is preferably formed by reacting a resin having a reactive functional group with a crosslinking agent. It is also preferable that either the reactive functional group or the crosslinking agent is self-crosslinked alone. However, the present invention does not exclude an embodiment in which the binder component is formed only of a resin having a reactive functional group or a crosslinking agent.
• resins having reactive functional groups examples include polyester resins, polyacrylic resins, polyurethane resins, and polyolefin resins. These resins preferably have at least one type of reactive functional group selected from the group consisting of carboxyl groups, hydroxyl groups, epoxy groups, and amino groups.
• the release layer of the present invention contains a crosslinking agent.
• crosslinking agents that are preferable include melamine-based, isocyanate-based, carbodiimide-based, oxazoline-based, and epoxy-based agents.
• One type of crosslinking agent may be used alone, or two or more types may be used in combination.
• Particularly preferable are crosslinking agents that react with reactive functional groups introduced into the binder component.
• the release layer of the present invention may contain particles having a particle size of 1 ⁇ m or less, but from the viewpoint of preventing pinhole formation, it is preferable that the layer does not substantially contain particles or other particles that form protrusions.
• Additives such as light release additives and heavy release additives, as well as adhesion improvers and antistatic agents, may be added to the release layer of the present invention in order to adjust the release force.
• pretreatment such as anchor coating, corona treatment, plasma treatment, and atmospheric pressure plasma treatment on the surface of the polylactic acid film before providing the release coating layer.
• the thickness of the release layer may be set according to the intended use, and is not particularly limited, but is preferably in the range of 0.005 to 2.0 ⁇ m after curing.
• a release layer thickness of 0.005 ⁇ m or more is preferable because it maintains peeling performance.
• a release layer thickness of 2.0 ⁇ m or less is preferable because it does not require too long a curing time and there is no risk of uneven thickness of the sheet due to a decrease in the flatness of the release film.
• the curing time is not too long, there is no risk of the resin constituting the release layer agglomerating and forming protrusions, and therefore it is preferable because pinhole defects in the sheet are unlikely to occur.
• the outer surface of the film on which the release layer is formed i.e., the outer surface of the release layer
• the arithmetic mean roughness (Sa) of the release layer surface is 10 nm or less and the maximum protrusion height (P) is 200 nm or less. It is more preferable that the arithmetic mean roughness of the release layer surface is 10 nm or less and the maximum protrusion height is 100 nm or less, and it is even more preferable that the arithmetic mean roughness of the release layer surface is 10 nm or less and the maximum protrusion height is 30 nm or less.
• the arithmetic mean roughness of the release layer surface is 10 nm or less and the maximum protrusion height is 200 nm or less, defects such as pinholes do not occur during sheet formation, and the yield is good, which is preferable. It can be said that the smaller the arithmetic mean roughness (Sa) of the release layer surface, the more preferable it is, but it may be 0.1 nm or more, or it may be 0.3 nm or more. The smaller the maximum protrusion height (P), the better, but it can be 1 nm or more, or 3 nm or more.
• the lower limit of the surface free energy of the release layer provided in the release film of the present invention is preferably 8 mJ/ m2 or more. More preferably, it is 10 mJ/ m2 or more, and even more preferably, it is 12 mJ/ m2 or more. When it is 8 mJ/ m2 or more, it is preferable because repelling and the like are unlikely to occur when a dissolving solution of the sheet is applied.
• the upper limit of the surface free energy of the release layer provided on the release film of the present invention is preferably 45 mJ/ m2 or less. More preferably, it is 40 mJ/ m2 or less, and even more preferably, it is 35 mJ/ m2 or less. If it is 45 mJ/ m2 or less, the releasability of the molded sheet is good, so it is preferable.
• the method of forming the release layer is not particularly limited, and a method is used in which a coating liquid in which a releasing resin is dissolved or dispersed is spread on one side of the base layer by coating or the like, the solvent is removed by drying, and then the coating is heated and dried, heat-cured, or cured with ultraviolet light.
• the drying temperature during solvent drying and heat-curing is preferably 180°C or less, more preferably 150°C or less, and most preferably 120°C or less.
• the heating time is preferably 30 seconds or less, and more preferably 20 seconds or less. If the temperature is 180°C or less, the flatness of the film is maintained and there is little risk of unevenness in the thickness of the sheet, which is preferable. If the temperature is 120°C or less, the film can be processed without impairing the flatness, and there is a further reduced risk of unevenness in the thickness of the sheet, which is particularly preferable.
• the surface tension of the coating liquid when applying the release layer is not particularly limited, but is preferably 30 mN/m or less.
• the coating liquid used to apply the release layer is not particularly limited, but it is preferable to add a solvent with a boiling point of 90°C or higher.
• a solvent with a boiling point of 90°C or higher By adding a solvent with a boiling point of 90°C or higher, bumping during drying can be prevented and the coating film can be leveled, improving the smoothness of the coating film surface after drying.
• the amount of solvent added is preferably about 10 to 80% by mass based on the total coating liquid.
• Examples of methods for applying the coating liquid include roll coating methods such as gravure coating and reverse coating, bar coating methods such as wire bars, die coating, spray coating, and air knife coating.
• a multilayer ceramic capacitor has a rectangular parallelepiped ceramic body. Inside the ceramic body, first internal electrodes and second internal electrodes are alternately provided along the thickness direction. The first internal electrodes are exposed at a first end face of the ceramic body. A first external electrode is provided on the first end face. The first internal electrode is electrically connected to the first external electrode at the first end face. The second internal electrode is exposed at a second end face of the ceramic body. A second external electrode is provided on the second end face. The second internal electrode is electrically connected to the second external electrode at the second end face.
• the release film for producing ceramic green sheets of the present invention is used to produce such multilayer ceramic capacitors.
• it is produced as follows. First, the release film of the present invention is used as a carrier film, and a ceramic slurry for forming a ceramic body is applied and dried. A conductive layer for forming the first or second internal electrode is printed on the applied and dried ceramic green sheet. A mother laminate is obtained by appropriately stacking and pressing the ceramic green sheet, the ceramic green sheet on which the conductive layer for forming the first internal electrode is printed, and the ceramic green sheet on which the conductive layer for forming the second internal electrode is printed. The mother laminate is divided into multiple pieces to produce raw ceramic bodies. The raw ceramic bodies are fired to obtain ceramic bodies. Then, the first and second external electrodes are formed to complete the multilayer ceramic capacitor.
• Thickness The thickness of the polylactic acid film was measured using a TH-104 manufactured by Tester Sangyo Co., Ltd.
• Crystallinity Measured using a differential scanning calorimeter (DSC214Polyma) manufactured by Netsch Japan Co., Ltd. Using 10 mg of sample, measurements were made in the range from 25°C to 250°C at a heating rate of 10°C/min, and the endothermic heat of the melting peak observed during heating was divided by the theoretical heat of fusion (93.6 J/g) of perfect crystals of polylactic acid to determine the crystallinity (%) of the polylactic acid film.
• DSC214Polyma differential scanning calorimeter
• Breaking strength and breaking elongation The breaking strength and breaking elongation of the polylactic acid film were measured in accordance with JIS C 2318. A sample was cut into a strip shape with a length of 120 mm and a width of 10 mm in the MD and TD directions of the film using a single-edged razor. The strip-shaped sample was then clamped with a chuck distance of 100 mm using an Autograph AG-IS manufactured by Shimadzu Corporation and pulled at a speed of 100 mm/min, and the breaking strength (MPa) and breaking elongation (%) in each direction were obtained from the obtained load-strain curve.
• the heat shrinkage of the polylactic acid film was measured in accordance with JIS C 2318.
• the laminated film was cut into a width of 10 mm and a length of 190 mm in the direction to be measured, and marks were made at 150 mm intervals, and the intervals between the marks (A) were measured.
• the film was placed in an oven in an atmosphere of 150°C, and heat-treated at 150 ⁇ 3°C for 30 minutes under no load, and the intervals between the marks (B) were measured.
• the heat shrinkage at 150°C was then calculated using the following formula.
• the film cut out in the same manner as above was placed in an oven in an atmosphere of 120°C, and heat-treated at 120 ⁇ 3°C for 30 minutes under no load, and the intervals between the marks (C) were measured, and the heat shrinkage at 120°C was calculated using the following formula.
• 150°C heat shrinkage rate (%) (A-B)/A x 100
• 120°C heat shrinkage rate (%) (A - C) / A x 100
• the haze (%) of the polylactic acid film was measured according to JIS K 7136 using a haze meter NDH-7000 II type manufactured by Nippon Denshoku Industries Co., Ltd.
• the total light transmittance (%) of the polylactic acid film was measured according to JIS K 7136 using a haze meter NDH-7000 II type manufactured by Nippon Denshoku Industries Co., Ltd.
• Example 1 Preparation of Polylactic Acid Resin Poly-L-lactic acid PLA L175 (weight ratio of L-lactic acid/D-lactic acid: 99/1) manufactured by Total Corbion was used as the polylactic acid resin.
• the extruded resin was cast onto a cooling drum with a surface temperature of 50°C and adhered to the surface of the cooling drum using an electrostatic application method, allowing it to cool and solidify, creating an unstretched film 400 ⁇ m thick.
• the unstretched sheet obtained was heated to 75°C using a group of heated rolls, and then stretched 3.0 times in the longitudinal direction using a group of rolls with different peripheral speeds.
• the uniaxially stretched film was then held with clips and stretched transversely at a temperature of 75° C. and a transverse stretch ratio of 4.96. Next, a heat treatment was carried out at 150° C. for 15 seconds.
• the biaxially stretched film that had been stretched in the TD direction was again held with clips and stretched transversely.
• the transverse stretching temperature was 170°C, and the transverse stretching ratio was 1.01 times.
• heat treatment was performed at 160°C for 15 seconds to obtain a polylactic acid film with a thickness of 40 ⁇ m.
• the physical properties of the film obtained in Example 1 are shown in Table 2.
• the polylactic acid film obtained had a high sum of the crystallinity and tensile modulus of elasticity and a low thermal shrinkage rate, indicating that a film with excellent modulus of elasticity and heat resistance was obtained in Example 1.
• Example 2 and 3 polylactic acid films were obtained in the same manner as in Example 1, except that the conditions were changed as shown in Table 1.
• the physical properties of the obtained films of Examples 2 and 3 are shown in Table 2.
• Example 2 a higher elastic modulus was obtained by increasing the second stretching ratio in the TD direction.
• Example 3 a relaxation treatment (160°C, relaxation rate 5%) was performed after TD stretching, thereby suppressing heat shrinkage in the TD direction and maintaining a high elastic modulus.
• the films of Examples 2 and 3 had a high sum of the crystallinity and the tensile elastic modulus, and a low thermal shrinkage rate, and therefore, it was shown that films excellent in elastic modulus and heat resistance were obtained in Examples 2 and 3.
• Example 4 Preparation of Polylactic Acid Resin
• poly-L-lactic acid PLA LX175 weight ratio of L-lactic acid/D-lactic acid: 96/4 manufactured by Total Corbion was used.
• the extruded resin was cast onto a cooling drum with a surface temperature of 50°C and adhered to the surface of the cooling drum using an electrostatic application method, allowing it to cool and solidify, creating an unstretched film 400 ⁇ m thick.
• the unstretched sheet obtained was heated to 70°C using a group of heated rolls, and then stretched 3.0 times in the longitudinal direction using a group of rolls with different peripheral speeds.
• the uniaxially stretched film was then held with clips and stretched transversely at a temperature of 75° C. and a transverse stretch ratio of 4.96. Next, a heat treatment was carried out at 150° C. for 15 seconds.
• the biaxially stretched film that had been stretched in the TD direction was again held with clips and stretched transversely.
• the transverse stretching temperature was 150°C, and the transverse stretching ratio was 1.01 times.
• a relaxation treatment was performed at 140°C for 15 seconds (relaxation rate 3%) to obtain a polylactic acid film with a thickness of 40 ⁇ m.
• the physical properties of the film obtained in Example 4 are shown in Table 2.
• the polylactic acid film obtained had a high sum of the crystallinity and tensile modulus of elasticity and a low thermal shrinkage rate, indicating that a film with excellent modulus of elasticity and heat resistance was obtained in Example 4.
• Example 5 In Example 5, a polylactic acid film was obtained in the same manner as in Example 3, except that an unstretched sheet was introduced into a simultaneous biaxial stretching machine, and while the ends of the film were held with clips, the sheet was stretched 3.0 times in the longitudinal direction and 5.0 times in the width direction in a hot air zone at a temperature of 75° C., and then the sheet was held again with clips and stretched laterally.
• the physical properties of the film obtained in Example 5 are shown in Table 2.
• the polylactic acid film obtained had a high sum of the crystallinity and the tensile modulus and a low thermal shrinkage, indicating that a film excellent in modulus and heat resistance was obtained in Example 5.
• the films obtained in Examples 1 to 5 have excellent elastic modulus and heat resistance, good dimensional stability when processed at high temperatures, and can obtain high rigidity. Furthermore, the films obtained in Examples 1 to 5 have a maximum projection height (P) of 200 nm or less and an arithmetic mean roughness (Sa) of 10 nm or less, so that when a release layer is formed on the surface of the film, it is possible to make the maximum projection height (P) of the surface 200 nm or less and the arithmetic mean roughness (Sa) of 10 nm or less.
• Comparative Examples 1 and 2 polylactic acid films were obtained in the same manner as in Examples 1 and 4, except that the conditions were changed as shown in Table 1.
• the physical properties of the obtained films of Comparative Examples 1 and 2 are shown in Table 2.
• Comparative Examples 1 and 2 are outside the scope of the present invention because they have a low tensile modulus and a high thermal shrinkage. Comparative Examples 1 and 2 were stretched using the commonly used sequential biaxial stretching or simultaneous biaxial stretching method, and because the stretching ratio was low, the modulus and heat resistance were poor.
• Comparative Example 3 a biaxially stretched film was obtained in the same manner as in Comparative Example 1, except that the conditions were changed to those shown in Table 1.
• the stretch ratio in the TD direction was set high in the commonly used sequential biaxial stretching, but stretching breakage occurred, and a polylactic acid film could not be obtained.
• the polylactic acid film and laminate film of the present invention are suitable for use, for example, as a release film for producing ceramic green sheets.

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