Biaxially oriented polylactic acid film, and laminated film

Abstract

To provide a polylactic acid film with excellent transparency and processability, relating to polylactic acid derived from biomass raw materials and being biodegradable. [Solution] The present invention relates to a biaxially oriented polylactic acid film formed from a film-forming material containing polylactic acid, wherein the mesophase orientation parameter of the polylactic acid film is (757 cm) in the spectrum measured by the total reflection method of Fourier transform infrared spectroscopy. -1 / 2996cm -1 The peak intensity ratio is 4.0 or less.

Description

[Technical Field]

[0001] The present invention relates to a biaxially oriented polylactic acid film formed from a film-forming material containing polylactic acid, and a laminated film containing the same. [Background technology]

[0002] Films made from polylactic acid (PLA) resin are derived from biomass raw materials and are biodegradable, so development is underway to replace conventional fossil fuels, and they are expected to replace polyethylene terephthalate, nylon, and polyolefins. However, compared to these raw materials, PLA is inferior in strength and heat resistance, regardless of whether it is for industrial or packaging use, so studies have been conducted to improve its mechanical properties and heat resistance by utilizing oriented crystallization through stretching.

[0003] For example, Patent Document 1 discloses a film suitable for heat moldability (heat resistance) and printability by controlling the surface orientation coefficient by controlling the stretching temperature and magnification and increasing the proportion of D-lactic acid. Patent Document 2 discloses a molded article with improved heat resistance and impact resistance by controlling the crystal structure by adding a crystal nucleating agent. In addition, Patent Documents 3 to 6 also disclose polylactic acid films. Furthermore, Patent Document 7 discloses a laminated film having an adhesive layer based on a polylactic acid film that eliminates internal crazing by controlling the degree of orientation by stretching temperature and magnification, thereby achieving both transparency and strength, heat resistance, and processability. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2005-15783 [Patent Document 2] Japanese Patent Publication No. 2009-249443 [Patent Document 3] Japanese Patent Publication No. 2003-170560 [Patent Document 4] Japanese Patent Application Publication No. 8-52171 [Patent Document 5] Japanese Patent Publication No. 2000-281816 [Patent Document 6] Japanese Patent Publication No. 2006-35787 [Patent Document 7] Patent No. 5775831 [Overview of the project] [Problems that the invention aims to solve]

[0005] In recent years, the need for environmental impact reduction activities, including SDGs and carbon neutrality, has increased, and the use of biomass-derived resins, such as PLA, is becoming increasingly active worldwide. However, it has been found that PLA, due to its brittleness, generates crazing inside the film when stretched. Crazing inside the film causes poor appearance (worsening haze) and cracking during processing. As a result of various studies by the inventors, it has become clear that internal crazing is particularly evident when the film contains inorganic particles and is stretched. Furthermore, while it is generally known that controlling the stretching temperature and magnification in uniaxial stretching and biaxial stretching processes is effective in controlling orientation and crystallinity, which are considered effective in improving mechanical properties and heat resistance, polylactic acid resin exhibits significant orientation and crystallization depending on the stretching temperature. In particular, low-temperature stretching causes crazing due to excessive stress, while high-temperature stretching induces defects such as fracture and puncture due to embrittlement associated with crystallization. In particular, with sequentially biaxially oriented films, the higher-order structures formed in each stretching process (uniaxial and biaxial) mutually influence each other, and we found that precise control of these higher-order structures is required to suppress creasing. Furthermore, when such biaxially oriented films or sheets are used as substrates for adhesive tapes, problems such as cracks and tears occur in the adhesive tapes during manufacturing and processing.

[0006] In Patent Document 1, a method for improving heat resistance is disclosed, but the heat resistance evaluation remains at 120°C, and an environment of 150°C with higher heat resistance is not disclosed. Also, it does not mention that crazes occur inside the film during stretching. In Patent Document 2, it does not mention crazes during stretching, and the haze reduction effect is also limited. In Patent Document 3, regarding the problem that void generation by an antiblocking agent causes haze deterioration, it is solved using a void inhibitor, but it can be said that the transparency of the obtained film is not sufficient. In Patent Document 4, it is a protective film for a lens, which has excellent transparency, but due to the low area magnification in the stretching process, it cannot be said that the compatibility between transparency and mechanical strength and heat resistance is satisfactory. In Patent Document 5, a method for improving slipperiness and processability by adding inorganic particles is disclosed, but a haze equivalent to that of pure L-lactic acid has not been achieved. Also, although low haze is achieved only when the amount of inorganic particle addition is reduced, the slipperiness required for proper processing is impaired. In Patent Document 6, it is a manufacturing method of a moisture-proof coated film of polylactic acid, and sequential biaxially stretched films are also mentioned, but from the high level of its haze, it cannot be said to be the optimal stretching temperature and ratio capable of suppressing crazes. Also, the biaxially oriented polylactic acid film has weak adhesion to printing inks, hard coats, etc., and may be inferior in processability. Also, the biaxially oriented polylactic acid film has high electrical insulation and is likely to be charged, so it may be inferior in processability.

[0007] Also, due to reasons in the molecular structure, PLA tends to have lower mechanical properties, heat resistance, and chemical resistance than other resins, so the problem was that it was difficult to apply in various uses. In Patent Document 7, a film is disclosed in which mechanical properties, heat resistance, and chemical resistance are improved by promoting crystallinity in the crystallization process that promotes crystallization after melt extrusion through film or sheet formation. By this effect, problems such as breakage or tearing in the production or processing of adhesive tapes, etc. when used as a base material for adhesive tapes, etc. are solved.

[0008] However, in Patent Document 7, although the base material's PLA film is environmentally friendly, the constituent materials used in the adhesive layer that is laminated are not environmentally friendly proposals and cannot sufficiently contribute to suppressing environmental impacts. Also, in Patent Document 7, there is no mention of biomass conversion regarding the adhesive layer or the release layer laminated on the laminated film, and it is difficult to say that all the resins constituting the laminated film contribute to suppressing environmental impacts.

[0009] An object of the present invention is to use polylactic acid derived from biomass raw materials and having biodegradability to eliminate internal crazes caused by stretching of PLA that are not disclosed in the above prior art, and to provide a biaxially oriented polylactic acid film that achieves both transparency and strength, heat resistance, and processability, and a laminated film including this as a base material film.

Means for Solving the Problems

[0010] As a result of the inventors of the present application intensively investigating polylactic acid films, the inventors of the present application found that by controlling the degree of orientation including the crystalline - amorphous intermediate layer (meso - layer) of the polylactic acid film, the occurrence of crazes accompanying stretching can be suppressed, and as an effect, haze reduction after stretching and cracking during processing can be suppressed. Furthermore, by controlling the crystallinity at the time of uniaxial stretching, higher crystallinity was realized by increasing the stretching temperature compared to the stretching temperature near the glass transition temperature, which was a general biaxial stretching method, and the heat resistance was enhanced. Thus, the biaxially oriented polylactic acid film of the present invention has succeeded in achieving both transparency and processability without sacrificing the conventional strength and heat resistance.

[0011] That is, the present invention is a biaxially oriented polylactic acid film formed from a film - forming material containing polylactic acid having the following configuration to solve the above problems. Furthermore, it is a laminated film including the biaxially oriented polylactic acid film. [Item 1] A biaxially oriented polylactic acid film formed from a film - forming material containing polylactic acid, In the spectrum measured by the total reflection method of Fourier transform infrared spectroscopy, the meso - phase orientation parameter (757 cm-1 / 2996cm -1 A biaxially oriented polylactic acid film having a peak intensity ratio of 4.0 or less. [Item 2] The biaxially oriented polylactic acid film according to Item 1, wherein the internal haze is 6% or less. [Item 3] A biaxially oriented polylactic acid film according to Item 1 or 2, wherein the breaking stress in the width direction is 100 MPa or more and the ratio of the breaking stress in the longitudinal direction to the width direction is 0.7 or less. [Item 4] A biaxially oriented polylactic acid film according to any one of items 1 to 3, wherein the thermal shrinkage rate in the longitudinal direction is 10% or less when heated at 150°C for 30 minutes. [Item 5] A biaxially oriented polylactic acid film according to any one of items 1 to 4, wherein the mass ratio of L-lactic acid to D-lactic acid is 100 / 0 to 85 / 15. [Item 6] The biaxially oriented polylactic acid film according to any one of items 1 to 5, wherein the arithmetic mean roughness (Sa) of at least one surface is 10 nm or less and the maximum protrusion height (P) is 200 nm or less. [Item 7] A laminated film comprising a base film and a release layer on at least one side of the base film, The aforementioned base film is a laminated film comprising a biaxially oriented polylactic acid film as described in any one of items 1 to 6. [Clause 8] The laminated film according to Clause 7, wherein the release layer is formed from a release layer forming material containing at least one selected from the group consisting of silicone resin, fluororesin, alkyd resin, wax, and aliphatic olefin as a release component. [Clause 9] The laminated film according to Clause 7 or 8, wherein the maximum protrusion 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. [Item 10] A laminated film according to any one of items 7 to 9, which is a release film for manufacturing ceramic green sheets. [Item 11] A laminated film comprising a base film and a resin layer on at least one side of the base film, The aforementioned resin layer is formed from a resin layer forming material containing an aqueous resin. The aforementioned base film is a laminated film comprising a biaxially oriented polylactic acid film as described in any one of items 1 to 6. [Item 12] The laminated film according to Item 11, wherein the surface free energy γs of the resin layer is 40 mN / m or more. [Clause 13] The laminated film according to Clause 11 or 12, wherein the resin layer is formed by an in-line coating method. [Item 14] The laminated film according to any one of items 11 to 13, wherein the resin layer forming material includes an antistatic agent. [Section 15] The surface resistivity of the resin layer is 1.0 × 10 14 A laminated film as described in item 14, which is less than or equal to Ω. [Section 16] The laminated film according to item 14 or 15, wherein the content of the antistatic agent is 5% by mass or more and 45% by mass or less with respect to the aqueous resin of the resin layer forming material. [Item 17] The laminated film according to any one of items 14 to 16, wherein the laminated film has a release layer on at least one side. [Clause 18] The laminated film according to Clause 17, wherein the release layer is formed from a release layer forming material containing at least one selected from the group consisting of silicone resin, fluororesin, alkyd resin, wax, and aliphatic olefin as a release component. [Clause 19] The laminated film according to Clause 17 or 18, wherein the maximum protrusion 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. [Item 20] A laminated film according to any one of items 17 to 19, which is a release film for the manufacture of ceramic green sheets. [Item 21] A laminated film comprising a base film and an adhesive layer on at least one side of the base film, The aforementioned base film is a laminated film comprising a biaxially oriented polylactic acid film as described in any one of items 1 to 6. [Section 22] The laminated film according to item 21, wherein the adhesive layer contains biomass-derived raw materials. [Section 23] The laminated film according to 22, wherein the adhesive layer is a layer containing an acrylic polymer, and at least one of the acrylic monomers that constitute the monomer component of the acrylic polymer is at least one selected from the group consisting of acrylic acid and methacrylic acid, which are biomass-derived raw materials. [Section 24] The laminated film according to item 11, having an adhesive layer on one side of the base film and a release layer on the side opposite to the side having the adhesive layer. [Section 25] The laminated film according to claim 24, wherein the release layer is formed from a release layer forming material containing at least one selected from the group consisting of silicone resin, fluororesin, alkyd resin, wax, and aliphatic olefin as a release component. [Section 26] The laminated film according to item 24 or 25, wherein the maximum protrusion height (P) on 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. [Effects of the Invention]

[0012] The biaxially oriented polylactic acid film of the present invention exhibits excellent transparency and processability through control of mesophase orientation. Therefore, it offers good dimensional stability during high-temperature processing and is suitable not only for packaging materials but also for optical applications requiring greater transparency and industrial components such as release paper. Furthermore, because it is made from biomass-derived raw materials and is biodegradable, it is possible to provide a superior biaxially oriented polylactic acid film that takes into account recent SDGs, and a laminated film using this as a base film, including a release layer, resin layer, adhesive layer, etc.

[0013] Furthermore, if the laminated film has an adhesive layer, using biomass-derived raw materials for the adhesive layer makes it possible to provide a laminated film in which both the base film and the adhesive layer are environmentally friendly, thus greatly contributing to the reduction of environmental impact. In addition, if the laminated film has a resin layer, antistatic properties can be imparted by including an antistatic agent in the resin layer. [Brief explanation of the drawing]

[0014] [Figure 1] Diagram illustrating the ATR-FTIR measurement method. [Figure 2] SEM cross-sectional image of the film from Example 2 [Figure 3] SEM cross-sectional image of the film of Comparative Example 1 [Figure 4] SEM cross-sectional image of the film of Comparative Example 3 [Modes for carrying out the invention]

[0015] The biaxially oriented polylactic acid film of the present invention is formed from a film-forming material containing polylactic acid. In this biaxially oriented polylactic acid film, the mesophase orientation parameter in the FT-IR spectrum is (757 cm⁻¹). -1 / 2996cm -1 It is preferable that the peak intensity ratio of the α-lactic acid film is 4.0 or less. Furthermore, it is preferable that the biaxially oriented polylactic acid film of the present invention has an internal haze of 6% or less, a breaking stress in the width direction of 100 MPa or more, and a ratio of breaking stress in the longitudinal direction to the width direction (longitudinal direction / width direction) of 0.7 or less. Furthermore, it is preferable that the thermal shrinkage rate in the longitudinal direction when heated at 150°C for 30 minutes is 10% or less. Furthermore, it is preferable that the mass ratio of L-lactic acid / D-lactic acid is 100 / 0 to 85 / 15.

[0016] A common method for producing biaxially oriented films using crystalline polymer materials by sequential biaxial stretching is, for example, in the case of PET (polyethylene terephthalate), to first obtain an unstretched sheet in a glassy state (amorphous state) by melt extrusion. Next, longitudinal stretching is performed by heating above the glass transition temperature and stretching several times to obtain a longitudinally uniaxially oriented film. Then, transverse stretching is performed by guiding the film to a tenter and stretching several times while heating above the glass transition temperature. After that, dimensional stability is imparted by crystallization (solidification) in a heat-fixing process. However, in the case of polylactic acid resin, it has been found that differences in transparency, i.e., haze, occur within the scope of the above film-making method. Specifically, for example, in the case of polylactic acid alone, crazing occurs inside the film depending on the thermal history and stretching ratio during the stretching process, and the haze and internal haze increase. Furthermore, when inorganic particles are included, crazing inside the film becomes more pronounced, and the overall haze also deteriorates. As factors, we focused on the deterioration of haze due to higher-order structure, namely molecular orientation and the progression of crystallization. However, since a correlation with haze could not be obtained from molecular orientation and crystallinity alone, we also focused on the mesophase, which represents the intermediate layer between crystalline and amorphous materials, as a more detailed higher-order structure. Through diligent investigation, we found a certain relationship between the mesophase orientation parameter and haze. In order to obtain a more transparent polylactic acid film by sequential biaxial stretching, it is preferable to control the crystalline form at the time of longitudinal stretching and the subsequent crystalline form during transverse stretching. The inventors considered that an increase in mesophase orientation ≈ excessive orientation, and that there is a possibility of craze occurring due to the breakdown of molecular chains.

[0017] (Biaxially oriented polylactic acid film) First, we will describe a biaxially oriented polylactic acid film formed from a film-forming material containing polylactic acid.

[0018] (Polylactic acid) 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 predetermined catalyst. The predetermined catalyst is, for example, tin or aluminum. The polylactic acid may contain L-lactic acid and D-lactic acid components as copolymer components or blended components. In polylactic acid films and resin compositions, the mass ratio of L-lactic acid (hereinafter referred to as L-form) to D-lactic acid (hereinafter referred to as 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. When the ratio of L-lactic acid (hereinafter referred to as L-form) to D-lactic acid (hereinafter referred to as D-form) is within the above range, high crystallinity can be obtained, making it easier to improve the properties of the film, such as increasing the physical properties of the film and decreasing the thermal shrinkage rate, which is preferable. Polylactic acid may also be copolymerized with hydroxy acid components other than lactic acid. Examples of hydroxy acid components other than lactic acid include glycolic acid, 3-hydroxypropionic acid, and 6-hydroxycaproic acid (ε-caprolactone).

[0019] In the present invention, the preferred glass transition temperature of polylactic acid is 40 to 70°C, the melting point is preferably 150 to 180°C, and orientation crystallization is preferably possible. A melting point of 155°C or higher is more preferable, and 160°C or higher is even more preferable. The glass transition temperature and melting point can be obtained by differential scanning calorimeter (DSC) or the like. The presence or absence of crystallinity can be confirmed by the presence or absence of a crystallization peak during the heating process or the cooling process after melting using DSC.

[0020] The reduced viscosity (ηsp / c) of the polylactic acid-containing film-forming material used in this invention is preferably in the range of 1.0 dl / g to 3.0 dl / g. When the reduced viscosity is 1.0 dl / g or higher, the molten polylactic acid-containing film-forming material can be stably extruded onto a cooling drum during film production, and the resulting biaxially oriented polylactic acid film can be prevented from tearing. When the reduced viscosity is 3.0 dl / g or lower, the increase in filtration pressure when filtering the molten polylactic acid-containing film-forming material during film production is reduced, making high-precision filtration easier.

[0021] The reduced viscosity (ηsp / c) of the biaxially oriented polylactic acid film of the present invention is preferably in the range of 1.0 dl / g to 2.5 dl / g. A reduced viscosity of 1.0 dl / g or higher is preferable because it does not cause many breaks during the stretching process. A reduced viscosity of 2.5 dl / g or lower is preferable because it has good cutability when cutting to a predetermined product width and does not cause dimensional defects.

[0022] In the film-forming material containing polylactic acid used in the present invention, copolymerized polylactic acid and polyesters other than polylactic acid may be used as a blend. The polyesters other than polylactic acid are preferably aliphatic polyesters, such as polybutylene succinate, polybutylene succinate adipate, polybutylene succinate tractate, polybutylene adipate terephthalate, and polyethylene succinate.

[0023] Even when copolymerized polylactic acid is used or when polyester components other than lactic acid are included, such as when blending with polyesters other than polylactic acid, the lactic acid component is preferably 85 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, and particularly preferably 97 mol% or more, of the total polyester components (total amount of hydroxycarboxylic acid component, dicarboxylic acid component, and glycol component). Furthermore, even when polyester components other than lactic acid are included, the glass transition temperature, melting point, and reduced viscosity of the copolymerized polylactic acid and the blend are preferably within the above ranges.

[0024] The polylactic acid-containing film-forming material used in the present invention may contain one or more additives depending on the purpose of use, such as inert particles including inorganic particles, heat-resistant polymer particles, and crosslinked polymer particles, fluorescent whitening agents, UV inhibitors, infrared absorbing dyes, heat stabilizers, surfactants, and antioxidants. As antioxidants, aromatic amine-based and phenol-based antioxidants can be used. As stabilizers, phosphorus-based (such as phosphoric acid and phosphate esters), sulfur-based, and amine-based stabilizers can be used. In the film-forming material, the polylactic acid content is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 97% by mass or more, particularly preferably 98% by mass or more, and most preferably 99% by mass or more. Furthermore, the glass transition temperature, melting point, and reduced viscosity measured for the film-forming material are preferably within the above ranges.

[0025] (Method for producing biaxially oriented polylactic acid film) The biaxially oriented polylactic acid film of the present invention is preferable in terms of mechanical strength, chemical resistance, heat resistance, and other factors.

[0026] The polylactic acid-containing film-forming material in this invention can be processed into an unstretched sheet by various methods, and then subjected to biaxial stretching to obtain a polylactic acid film. As for the production method of the unstretched sheet, a solution casting method and a melt extrusion method can be used. The melt extrusion method is preferred in this invention.

[0027] The melting temperature of the film-forming material is preferably in the range of 150 to 250°C, more preferably 180 to 245°C, and even more preferably 200 to 240°C. A melting temperature of 150°C or higher is preferable because it results in a suitable melt viscosity and high productivity. A melting temperature of 250°C or lower is preferable because it suppresses thermal degradation of polylactic acid.

[0028] The die temperature during melt extrusion is the same as described above, but preferably it is in the range of 150 to 300°C, more preferably 170 to 290°C, and even more preferably 180 to 240°C. When the die temperature during melt extrusion is 150°C or higher, the melt viscosity is within a suitable range, and stable extrusion is possible. When the temperature is 300°C or lower, thermal decomposition of the resin can be suppressed.

[0029] The biaxially oriented polylactic acid film of the present invention can be manufactured according to a general method for manufacturing polyester films, and preferably does not contain additives such as plasticizers or crystallization accelerators. For example, one method involves melting polyester resin, extruding it into a sheet, uniaxially stretching the unoriented polyester in the longitudinal direction (vertical direction) using the difference in roll speeds at a temperature above the glass transition temperature, then biaxially stretching it transversely using a tenter, and finally heat-treating it. Specifically, for example, in the longitudinal stretching step in the longitudinal direction, it is preferable to heat the film and stretch it to 1.1 to 6.0 times between two or more rolls with different peripheral speeds. From the viewpoint of strength and quality after biaxial stretching, the lower limit of the longitudinal stretching ratio is preferably 2.0 times, more preferably 2.5 times, even more preferably 2.8 times, even more preferably 3.0 times, even more preferably 3.2 times, and most preferably 3.5 times. Furthermore, from the viewpoint of transverse stretching permeability in biaxial stretching, the upper limit of the longitudinal stretching ratio is preferably 6.0 times, more preferably 5.0 times, even more preferably 4.0 times, even more preferably 3.5 times, even more preferably 3.2 times, and most preferably 3.0 times. The preferred range of longitudinal stretching ratios can be arbitrarily selected and combined within a range where the lower limit and upper limit are the same or not reversed.

[0030] The heating method at this time may be a method using a heating roll or a method using a non-contact heating medium, or a combination of both. In this case, it is preferable to set the temperature of the film in the range of (Tg-10℃) to (Tg+50℃). More preferably (Tg-5℃) to (Tg+40℃), and even more preferably (Tg-0℃) to (Tg+30℃), with the upper limit being more preferably (Tg+20℃), even more preferably (Tg+15℃), and particularly preferably (Tg+12℃). Furthermore, from the viewpoint of film permeability during subsequent transverse stretching, it is preferable that the degree of crystallinity of the film at the time of longitudinal uniaxial stretching be in the range of 20% to 50%. More preferably 25% to 45% is preferred, and if the degree of crystallinity is not within the appropriate range, there is a possibility that the film will not be stretched uniformly in the width direction during subsequent transverse stretching, and the permeability may deteriorate at the transverse stretching temperature required to eliminate the craze inside the film as described below.

[0031] Because PLA has a lower crystallization temperature for orientation compared to PET, when stretching with heated rolls between rolls, high temperatures (e.g., roll temperature of 70°C or higher) can lead to increased mesophase orientation as crystallization progresses during stretching, potentially resulting in high haze. Therefore, it is preferable to shorten the time the film is exposed to high temperatures during longitudinal uniaxial stretching. Specific methods include, for example, setting the temperature lower before the final roll on the low-speed side and raising the temperature of the final roll, or preheating the rolls and then intensively heating the stretching point with an infrared heater. Even when using an infrared heater, it is preferable to adjust the output to prevent it from exceeding an appropriate temperature, as infrared heaters tend to overheat easily.

[0032] Next, the longitudinally uniaxially oriented film is introduced into a tenter and preferably stretched 1.1 to 10 times in the width direction at a temperature of (Tg-10℃) to Tm or lower. A more preferred range for transverse stretching temperature is (Tg-0℃) to (Tg+30℃), even more preferably (Tg+10℃) to (Tg+40℃), even more preferably (Tg+20℃) to (Tg+50℃), and most preferably (Tg+30℃) to (Tg+60℃). A more preferred range for stretching ratio is 3.0 to 6.0 times, even more preferably 3.5 to 5.5 times, and even more preferably 4.0 to 5.0 times. In this invention, the mesophase orientation is controlled and film permeability is ensured by balancing the degree of crystallinity, temperature, and magnification during the sequential biaxial stretching process, thereby suppressing the appearance of crazes, i.e., suppressing internal haze. It is particularly preferable to set the stretching temperature in the width direction in the range of (Tg+30°C) to (Tg+60°C) and the stretching magnification to 4.0 to 5.0 times.

[0033] In these transverse stretching processes, it is necessary to consider the progress of crystallization during the preheating process in the tenter, the temperature during the stretching process, and the balance between the progress of crystallization and stress. If the temperature is low, the mesophase around the crystals formed during longitudinal stretching does not dissolve sufficiently, and the orientation of the mesophase tends to increase. On the other hand, if the temperature is too high, the crystallization progresses too quickly, resulting in an imbalance, and because highly oriented crystallization progresses during stretching, the orientation of the mesophase around the crystals also increases, which can make the film prone to breakage. Specifically, for example, it is preferable to set the preheating temperature to a low temperature of 80°C or less to prevent crystallization from progressing during preheating, and then gradually increase the temperature (e.g., above 80°C) as stretching progresses. This method can reduce the stress on the mesophase and suppress the orientation parameter. It is also necessary to consider the relationship with the degree of crystallization at the time of longitudinal uniaxial stretching, and if the degree of crystallization is high at the time of longitudinal uniaxial stretching, it is preferable to raise the transverse stretching temperature to a higher temperature (e.g., above 90°C). Furthermore, these factors must also be considered in relation to the lateral stretching ratio. When the lateral stretching ratio is high, the stress on the mesophase tends to increase, so it is preferable to raise the lateral stretching temperature. For example, if the ratio exceeds 4.0, a temperature of 100°C or higher is preferable.

[0034] Furthermore, after stretching is complete, in order to reduce the thermal shrinkage rate of the film, it is preferable to perform a thermal setting treatment within 30 seconds, preferably within 10 seconds, during the thermal setting process, and to perform a longitudinal relaxation treatment of 0.5 to 10%, a transverse relaxation treatment, etc. These relaxation treatments result in a film with reduced thermal shrinkage rate. When the obtained film (biaxially oriented polylactic acid film) is used as a base film and an adhesive layer is provided, the resulting laminated film (such as adhesive tape) can be used effectively even under high temperature conditions of, for example, 150°C, suppressing melting and deformation, and can be used sufficiently in applications requiring heat resistance.

[0035] The heat-fixing temperature is preferably in the range of 90 to 180°C. The lower limit of the heat-fixing temperature is more preferably 110°C, even more preferably 120°C, and particularly preferably 130°C. The lower limit of the heat-fixing temperature is more preferably 170°C, and particularly preferably 160°C. By setting the temperature within the above range, orientation crystallization can be promoted while mitigating excessive orientation distortion, making it easier to achieve an appropriate orientation for the mesophase. Furthermore, it is preferable to increase the dimensional stability of the film due to heat and suppress the phenomenon of holes forming in the film due to heat. By increasing these heat-fixing temperatures, a film with reduced thermal shrinkage can be obtained. When the obtained film (biaxially oriented polylactic acid film) is used as a base film and an adhesive layer is provided, the resulting laminated film (such as adhesive tape) can suppress melting and deformation even under high temperature conditions of, for example, 150°C, and can be used sufficiently in applications requiring heat resistance.

[0036] If the permeability and suppression of creasing inside the film cannot be reproduced by the temperature range of each zone in the tenter during the transverse stretching process described above, it is also possible to adjust the airflow velocity in each zone, and if the film heating is insufficient, it is preferable to increase the airflow velocity.

[0037] (Physical properties of biaxially oriented polylactic acid film) The thickness of the biaxially oriented polylactic acid film of the present invention is preferably 2 μm or more and 500 μm or less, more preferably 15 μm or more and 400 μm or less, and even more preferably 20 μm or more and 250 μm or less. When the thickness of the biaxially oriented polylactic acid film is 2 μm or more, the biaxially oriented polylactic acid film has minimum rigidity and is easy to handle. Furthermore, when the thickness of the biaxially oriented polylactic acid film is 500 μm or less, the transportability of the film when transporting the film on multiple rolls and the handlingability of the manufactured film are improved, making it easier to handle.

[0038] Mesophase orientation parameter of biaxially oriented polylactic acid film (757cm²) -1 / 2996cm -1 The upper limit of the peak intensity ratio is preferably 4.0 or less. The preferred upper limit of the mesophase orientation parameter is 3.9, a more preferred upper limit is 3.8, an even more preferred upper limit is 3.7, and the most preferred upper limit is 3.6. A mesophase orientation parameter of 4.0 or less is preferable because it suppresses excessive orientation, resulting in sufficient transparency of the film and suppressing crazing and internal haze caused by transparency. The mesophase orientation parameter is preferably 3.0 or higher, more preferably 3.2 or higher, even more preferably 3.4 or higher, and particularly preferably 3.5 or higher. Setting the mesophase orientation parameter to the above levels makes it easier to obtain the strength required for a biaxially oriented film.

[0039] The internal haze of the biaxially oriented polylactic acid film is preferably 6% or less. A more preferable upper limit for internal haze is 3%, an even more preferable upper limit is 2%, and a particularly preferable upper limit is 1%. Further upper limits are preferred in the order of 0.8%, 0.5%, and 0.1%. An internal haze of 6% or less is preferable because it provides sufficient transparency for the film and makes it suitable for optical applications and industrial components such as release paper. Furthermore, suppressing internal haze (i.e., suppressing craze) is preferable because it suppresses cracking and tearing during the film processing process.

[0040] The biaxially oriented polylactic acid film preferably has a breaking stress in the width direction of 100 MPa or more, and the ratio of the breaking stress in the longitudinal direction (vertical direction) to the breaking stress in the width direction is preferably 0.7 or less. The preferred lower limit for the breaking stress in the width direction is 100 MPa, a more preferred lower limit is 150 MPa, an even more preferred lower limit is 200 MPa, and an even more preferred lower limit is 230 MPa. A breaking stress in the width direction of 100 MPa or more is preferable because it provides sufficient mechanical strength to the film and suppresses defects such as elongation and slippage during the film processing process. Considering manufacturing points, the upper limit for the breaking stress in the width direction is considered to be 1000 MPa.

[0041] Furthermore, the preferred lower limit for the ratio of fracture stress in the longitudinal direction to the width direction is 0.3, the more preferred lower limit is 0.33, and the still preferred lower limit is 0.35. A ratio of 0.7 or less is preferable in terms of transparency.

[0042] Furthermore, it is preferable to control the longitudinal fracture stress to satisfy the aforementioned ratio, specifically, preferably 50 to 200 MPa, more preferably 60 to 170 MPa, even more preferably 65 to 150 MPa, and even more preferably 70 to 130 MPa. Controlling the longitudinal fracture stress within this range is preferable from the viewpoint of stable film formation.

[0043] The tensile modulus in the width direction of the biaxially oriented polylactic acid film is preferably 2.0 GPa or higher. The preferred lower limit of the tensile modulus is 3.0 GPa, a more preferred lower limit is 3.5 GPa, an even more preferred lower limit is 4.0 GPa, and an even more preferred lower limit is 4.5 GPa. A tensile modulus in the width direction of 4.0 GPa or higher is preferable because it provides sufficient rigidity to the film and suppresses the occurrence of wrinkles and warping. Considering manufacturing points, the upper limit of the tensile modulus in the width direction is considered to be 10.0 GPa.

[0044] Furthermore, the tensile modulus of elasticity in the longitudinal direction of the polylactic acid film is preferably 1.5 to 3 GPa. The tensile modulus of elasticity in the longitudinal direction is preferably 1.6 to 2.8 GPa, more preferably 1.7 to 2.6 GPa, and even more preferably 1.8 to 2.5 GPa. Controlling the tensile modulus of elasticity in the longitudinal direction within the above range is preferable from the viewpoint of stable film formation.

[0045] In biaxially oriented polylactic acid films, it is preferable that the thermal shrinkage rate in the longitudinal direction (vertical direction) is 10.0% or less when heated at 150°C for 30 minutes. When heated at 150°C for 30 minutes, the preferred upper limit of the thermal shrinkage rate in the longitudinal direction is 8.0% or less, more preferably 5.0% or less, even more preferably 4.0% or less, even more preferably 3.0% or less, particularly preferably 2.0% or less, and most preferably 1.0% or less. A low thermal shrinkage rate in the longitudinal direction facilitates processing such as coating and suppresses appearance defects caused by deformation of the film under high heat. While a low thermal shrinkage rate in the longitudinal direction is preferable, from a manufacturing standpoint, 0.01% is considered the lower limit.

[0046] Furthermore, when the biaxially oriented polylactic acid film is heated at 150°C for 30 minutes, the thermal shrinkage rate in the width direction is preferably 0 to 15%. The thermal shrinkage rate in the width direction is preferably 12% or less, more preferably 10% or less, even more preferably 7% or less, and even more preferably 5% or less. The thermal shrinkage rate in the width direction may be 0.1% or more, 0.5% or more, or 1% or more. Controlling the thermal shrinkage in the width direction within the above range is preferable from the viewpoint of processability.

[0047] The surface of the biaxially oriented polylactic acid film of the present invention is preferably smooth and has low haze. In particular, low haze is preferred when used as a release film for ceramic green sheet manufacturing or for optical applications. The internal haze is preferably 6% or less, preferably 3% or less, more preferably 2% or less, and most preferably 1% or less. The lower limit of the haze is preferable as much as possible, but it may be 0.1% or more, or 0.3% or more. From the perspective of reducing haze, it is preferable to suppress surface irregularities of the film, but from the viewpoint of handling on a rotating roll, it is preferable to form certain irregularities on at least one surface to provide a certain degree of slipperiness.

[0048] The degree of crystallinity of the biaxially oriented polylactic acid film is preferably 40% to 90%. It is more preferably 50% to 85%, and even more preferably 55% to 80%. A degree of crystallinity in the range of 40% to 90% is preferable because it improves strength and provides a high modulus of elasticity.

[0049] Furthermore, when forming a smooth release layer or the like on the surface of a biaxially oriented polylactic acid film, it is preferable that at least one surface of the polylactic acid film is also smooth. The smooth surface of the polylactic acid film preferably has an arithmetic mean roughness (Sa) of 10 nm or less and a maximum protrusion height (P) of 200 nm or less. More preferably, the surface has an arithmetic mean roughness of 10 nm or less and a maximum protrusion height of 150 nm or less; even more preferably, the surface has an arithmetic mean roughness of 10 nm or less and a maximum protrusion height of 120 nm or less; and still preferably, the surface has an arithmetic mean roughness of 8 nm or less and a maximum protrusion height of 120 nm or less. If the surface has an arithmetic mean roughness of 10 nm or less and a maximum protrusion height of 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 0.3 nm or more. Furthermore, the maximum surface protrusion height (P) may be 1 nm or more, or 3 nm or more.

[0050] (Laminated film) The biaxially oriented polylactic acid film of the present invention can be used as a base film in, for example, the following laminated film configuration. Furthermore, to improve the peel strength of the laminated film, the surface of the base film may be subjected to corona treatment, plasma treatment, or the like.

[0051] One embodiment of the laminated film of the present invention is a base film containing a biaxially oriented polylactic acid film and a resin layer on at least one side of the base film (however, the resin layer does not include the release layer of laminated film (2) or the adhesive layer of laminated film (3) described below). Hereinafter, this will be referred to as laminated film (1). Furthermore, one embodiment of the laminated film of the present invention is one in which a base film containing a biaxially oriented polylactic acid film and a release layer are provided on at least one side of the base film. Hereinafter, this will be referred to as laminated film (2). Furthermore, one embodiment of the laminated film of the present invention is one in which a base film containing a biaxially oriented polylactic acid film and an adhesive layer are provided on at least one side of the base film. Hereinafter, this will be referred to as laminated film (3).

[0052] (Laminated film (1)) The resin layer of the laminated film (1) described above can be provided on one or both sides of the base film. If provided on both sides, the resin layers may be the same or different. Different resin layers mean that at least one of the resin layers has a different composition or thickness. If they are different, it is preferable that the resin layers have different compositions.

[0053] (Resin layer) Examples of the resin layer include functional layers such as polyester layers other than polylactic acid, easy-adhesion layers, antistatic layers, slip-enhancing layers, barrier layers, ultraviolet-absorbing layers, antibacterial layers, and antifouling layers. An easy-adhesion layer can be provided to improve the adhesion between the biaxially oriented polylactic acid film and adhesive layers or hard coat layers. A slip-enhancing layer can be provided by adding particles to the coat layer to create irregularities in order to ensure a certain degree of slipperiness for neat winding of the biaxially oriented polylactic acid film. The resin layer can be formed as one or two or more layers.

[0054] The resin layer is preferably formed from a resin layer forming material containing an aqueous resin. The resin layer forming material contains an aqueous resin and more preferably contains lubricant particles. By having the resin layer (e.g., an easy-adhesion layer, an easy-slip layer), depending on the function of the resin layer, the adhesion of the laminated film (1) is improved while maintaining the high transparency that is a characteristic of the biaxially oriented polylactic acid film of the present invention, and easy slipperiness is also provided in the production of film rolls. Note that aqueous resin means a resin that is water-soluble or water-dispersible, and is a resin that can be used as an aqueous coating solution. The aqueous resin preferably has hydrophilic groups such as carboxylic acid groups, sulfonic acid groups, carboxylic acid bases, sulfonic acid bases, and hydroxyl groups.

[0055] The aqueous resin is not particularly limited, but from the viewpoint of controlling the surface free energy γs of the resin layer described later, it is preferable that it be mainly composed of at least one of polyester resin, polyurethane resin, or acrylic resin. Here, "main component" refers to a component that accounts for 50% or more by mass of the solid components constituting the resin layer. The forming material (coating liquid) used to form the resin layer of the present invention is preferably an aqueous coating liquid containing at least one of water-soluble or water-dispersible copolymer polyester resin, acrylic resin, and polyurethane resin. The aqueous resin is also preferable from the viewpoint of suppressing the shedding of the antistatic agent when the antistatic agent described later is contained in the resin layer.

[0056] The aqueous resin of the present invention may contain two or more types of resins to improve adhesion. For example, to achieve both adhesion and heat and humidity resistance, two or more different resins may be used in combination, such as polyester resin and polyurethane resin, polyester resin and acrylic resin, or polyurethane resin and acrylic resin. Alternatively, two or more polyester resins with different glass transition temperatures may be used.

[0057] In the present invention, a crosslinking agent may be included in the resin layer forming material in order to form a crosslinked structure in the resin layer. By including a crosslinking agent, it is possible to further improve adhesion under high temperature and high humidity conditions. Examples of crosslinking agents include urea-based, epoxy-based, melamine-based, isocyanate-based, oxazoline-based, and carbodiimide-based agents. Among these, melamine-based, isocyanate-based, oxazoline-based, and carbodiimide-based agents are preferred due to their effect on the long-term stability of the coating liquid and the improvement of adhesion under high temperature and high humidity treatment. In addition, catalysts and the like may be used as appropriate as needed to promote the crosslinking reaction.

[0058] The crosslinking agent content in the resin layer forming material is preferably 1% by mass or more and 50% by mass or less of the total solid components. More preferably, it is 5% by mass or more and 30% by mass or less. A content of 5% by mass or more increases the strength of the resin in the resin layer and its adhesion under high temperature and high humidity conditions, while a content of 5% by mass or more increases the flexibility of the resin in the resin layer and helps to suppress the decrease in adhesion under room temperature, high temperature, and high humidity conditions.

[0059] The lubricant particles may be inorganic particles or organic particles, or a combination of both. The inorganic particles are not particularly limited, but examples include silica, kaolinite, talc, light calcium carbonate, heavy calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, titanium dioxide, zirconium dioxide, tin oxide, satin white, aluminum silicate, diatomaceous earth, calcium silicate, aluminum hydroxide, hydrated halloysite, magnesium carbonate, and magnesium hydroxide.

[0060] The organic particles are not particularly limited, but examples include particles of polystyrene, melamine resin, acrylic, acrylic-styrene, silicone, benzoguanamine resin, benzoguanamine-formaldehyde condensate resin, polycarbonate, polyethylene, etc., and it is preferable that these resin particles are three-dimensionally crosslinked.

[0061] By incorporating lubricant particles, slipperiness can be imparted, which can suppress wrinkle formation when winding the film during film manufacturing processes, and blockage (film sticking together due to tightening over time) when wound film rolls are stored for long periods.

[0062] The average particle size of the lubricant particles is not particularly limited, but from the viewpoint of maintaining the transparency of the film, an average particle size of 1 to 500 nm is preferred, and 1 to 100 nm is more preferred. The average particle size is measured using a Coulter counter (Beckman Coulter, Multisizer Type II) after dispersing the particles in a solvent that does not cause swelling. Two or more types of particles with different average particle sizes may be used for the lubricant particles, and any combination of inorganic particles, organic particles, or inorganic and organic particles may be used.

[0063] The content of the lubricant particles in the resin layer is preferably 0.1% by mass or more and 30% by mass or less of the total solid content of the resin layer forming material, and more preferably 1% by mass or more and 20% by mass or less. A content above this level makes it easier to obtain sufficient blocking resistance and improve scratch resistance. A content below this level makes it easier to increase the transparency and coating strength of the resin layer.

[0064] The resin layer forming material may also contain a surfactant to improve leveling performance during coating and to degas the coating liquid. The surfactant can be cationic, anionic, or nonionic, but silicone-based, acetylene glycol-based, or fluorine-based surfactants are preferred. These surfactants are preferably included in the resin layer to an extent that does not impair adhesion to other functional layers, adhesive layers, and release layers laminated on the resin layer.

[0065] The resin layer forming material may contain various additives to impart other functionalities to the resin layer, to the extent that it does not impair adhesion with other functional layers, adhesive layers, and release layers. Examples of such additives include fluorescent dyes, fluorescent whitening agents, plasticizers, ultraviolet absorbers, pigment dispersants, antifoaming agents, defoaming agents, preservatives, and antistatic agents.

[0066] Because polylactic acid films have high electrical insulation properties, they are prone to static charge buildup, which can lead to problems such as repelling during coating and printing, and overlapping during sheet-fed processing. To prevent this, it is preferable that the resin layer contains an antistatic agent as an additive. The antistatic agent is not particularly limited, but including an antistatic agent in the resin layer reduces static charge buildup during film transport in printing processes, suppressing dust adhesion and reduced processability due to film-to-film adhesion caused by triboelectric charging.

[0067] Examples of antistatic agents include ionic conductive types and conductive polymer types, and those that can suppress migration to other articles in contact or to the back surface of the film itself are preferred. For example, ionic conductive types include nonionic types such as sorbitan type, ether type, ester type, sorbitol type, and glucose type; cationic types such as quaternary ammonium salt type, quaternary ammonium resin type, imidazoline type, Arcover type, and Solomin A type; anionic types such as alkyl sulfate type, alkyl phosphate type, phosphate ester salt type, and sulfate ester salt type; and amphoteric surfactant types such as betaine type, amino acid type, and aminosulfate ester type, or polymer types. Since aqueous resins used in resin layers are generally used as aqueous dispersions, anionic antistatic agents are preferred for their dispersibility and stability in the coating solution.

[0068] As for the conductive polymer type, π-electron conjugated conductive polymers can be suitably used. Unlike the ionic conductive type described above, π-electron conjugated conductive polymers are suitable because they can provide stable and effective antistatic properties even under low humidity conditions. As for the π-electron conjugated conductive polymer, it is preferable that its repeating units are aniline and / or its derivatives, pyrrole and / or its derivatives, isothianaphthene and / or its derivatives, acetylene and / or its derivatives, thiophene and / or its derivatives, etc. Among these, thiophene and / or its derivatives are particularly preferred because they produce less coloration.

[0069] The content of the antistatic agent contained in the resin layer is preferably 5% to 45% by mass based on the aqueous resin of the resin layer forming material. The antistatic agent can reduce the charging on the surface of the resin layer and suppress troubles during printing. The content of the antistatic agent is more preferably 7% or more by mass, and even more preferably 8% or more by mass. The upper limit may be 40% by mass or less. By setting the content of the antistatic agent above the above range, the required antistatic property can be exhibited, and troubles during printing such as appearance defects can be suppressed. Also, by setting the content of the antistatic agent below the above range, the wettability of the resin layer surface can be appropriately controlled, and back transfer and blocking in the film roll body due to excessive addition can be suppressed. Note that the antistatic agent is contained in the resin layer in an amount within the above range.

[0070] The antistatic property of the laminated film (1′) with a resin layer containing an antistatic agent is such that the surface resistivity of the resin layer surface is preferably 1.0×10 14 Ω / sq or less, more preferably 1.0×10 13 Ω / sq or less, and most preferably 1.0×10 12 Ω / sq or less. By setting it below the above value, the charging during film conveyance during printing processing can be reduced, and the deterioration of processability due to dust adsorption and the adsorption of films due to frictional charging can be suppressed. The surface resistivity of the resin layer surface is preferably 1.0×10 9 Ω / sq or more, more preferably 5.0×10 9 Ω / sq or more, and may be 1.0×10 10 Ω / sq or more. By setting it above the above value, it is possible to make it difficult for bleed-out of the antistatic agent to occur.

[0071] In the present invention, a method for providing a resin layer on a substrate film having a biaxially oriented polylactic acid film is to apply a resin layer forming material (coating liquid) containing a solvent, particles, and resin to the substrate film and dry it. As the solvent, water or a mixture of water and a water-soluble organic solvent is preferred from the viewpoint of environmental issues, and the amount of water solvent in the coating liquid is preferably 50 to 95% by mass, and particularly preferably 60 to 90% by mass.

[0072] In the present invention, the solid content concentration in the coating solution is preferably 0.5 to 35% by mass, and particularly preferably 1.0 to 15% by mass.

[0073] Any known method can be used to apply the coating solution to the substrate film. Examples include the reverse roll coating method, gravure coating method, kiss coating method, die coater method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, impregnation coating method, curtain coating method, and the like. These methods can be used individually or in combination for coating.

[0074] The method for forming the resin layer is not particularly limited, and conventionally known methods such as coating methods can be used. Among coating methods, preferred methods include coating after manufacturing the biaxially oriented film (offline coating method) and coating during the biaxially oriented film manufacturing process (in-line coating method) when coating the surface of the film. The in-line coating method is preferred because it provides good adhesion between the base film and the resin layer, and minimizes deterioration of the mechanical properties of the base film during manufacturing and reduces thermal wrinkles. In the case of the in-line coating method performed in the manufacturing process of a biaxially oriented polylactic acid film, the drying and heat treatment conditions during coating depend on the coating thickness and the conditions of the equipment, but it is preferable to immediately send the film to the stretching process in the perpendicular direction after coating and dry it in the preheating zone or stretching zone of the stretching process, and in such cases, it is usually preferable to set the temperature to around 50 to 120°C. Furthermore, the heat treatment process after stretching depends on the required mechanical properties of the base film and the conditions of the equipment, but it is preferable to perform heat treatment at a temperature of 130°C or higher from the viewpoint of improving the adhesive strength between the base film and the resin layer. For the aforementioned resin layers, it is preferable to use an inline coat for an easy-adhesion layer to improve adhesion, an easy-slip layer to provide slipperiness, etc.

[0075] In the in-line coating method, the resin layer is formed by applying the coating solution to an unstretched or uniaxially stretched polylactic acid film, drying it, stretching it at least uniaxially, and then performing a heat treatment.

[0076] Furthermore, if the resin layer is provided as an in-line coating layer during the stretching and film-forming process when manufacturing a biaxially oriented polylactic acid film, the in-line coating layer is obtained in a laminated state at the time the biaxially oriented polylactic acid film is manufactured.

[0077] The thickness of the resin layer in the present invention is preferably 1 μm or less. When the resin layer is formed by an in-line coating method, the final thickness of the resin layer is preferably 20 nm to 500 nm, more preferably 30 nm to 300 nm, and even more preferably 30 nm to 200 nm. By making the thickness of the resin layer 20 nm or more, it becomes easier to obtain the high effect on lubricity required in the present invention. On the other hand, by making the thickness of the resin layer 500 nm or less, it becomes easier to suppress the increase in haze and the decrease in transparency.

[0078] In the present invention, it is preferable that the surface free energy γs of the final resin layer is 40 mN / m or more. Since polylactic acid film has poorer wettability than general polyester film, setting the surface free energy γs to 40 mN / m or more improves the coatability of the aqueous resin, makes it easier to achieve uniform thickness when laminating the resin layer, suppresses uneven coating and repelling which result in poor coating appearance, and also suppresses localized reduction in lubricity by unevenly distributing the lubricant particles contained in the resin layer, making it less likely for wrinkles to occur when winding the film. Furthermore, it is preferable that the above surface free energy γs be as large as possible in terms of manufacturing, but since a larger value increases hydrophilicity and makes the surface of the resin layer more susceptible to moisture absorption, it is preferable that it be 80 mN / m or less. The above surface free energy γs may be 70 mN / m or less, 60 mN / m or less, 55 mN / m or less, or 50 mN / m or less.

[0079] The static friction coefficient and dynamic friction coefficient of the laminated film (1) of the present invention are preferably both 0.40 or more and 0.70 or less. If it is less than 0.40, winding misalignment is likely to occur when the film roll is transported. On the other hand, if it exceeds 0.70, the lubricity decreases, and wrinkles are likely to occur when the film is wound up. The static friction coefficient and dynamic friction coefficient are more preferably 0.68 or less, and even more preferably 0.66 or less. Note that the static friction coefficient and dynamic friction coefficient are values ​​measured by overlapping one surface of the laminated film (1) with the other surface.

[0080] (Laminated film (2)) The release layer of the laminated film (2) described above can be provided on one or both sides of the base film. Preferably, the release layer is provided on the outermost surface of the laminated film (2). Furthermore, the embodiment of the laminated film (2) having the release layer can be applied together with the embodiment of the laminated film (1). That is, as the base film of the laminated film (2) having a release layer, the biaxially oriented polylactic acid film of the present invention can be used, as well as the laminated film (1). When the release layer is applied to the embodiment of the laminated film (1), the release layer may be provided on the resin layer surface, or it may be provided directly on the base film containing the biaxially oriented polylactic acid film without going through the resin layer. Furthermore, when the release layer is provided on one side of the base film, it is preferable that the side of the base film opposite to the release layer is the resin layer, and it is preferable that the release layer is directly laminated on one side of the base film and the resin layer is provided on the other side.

[0081] (Release layer) The aforementioned release layer is formed from a release layer forming material, and the resin constituting the release component is not particularly limited. Silicone resins, fluororesins, alkyd resins, various waxes, aliphatic olefins, etc., can be used, and each resin can be used alone or in combination of two or more types. Preferably, the release layer contains a silicone release component such as a silicone resin or silicone oil.

[0082] For example, silicone resin refers to a resin having a silicone structure within its molecule. Examples include curable silicone, silicone graft resin, and modified silicone resin such as alkyl-modified silicone. However, from the viewpoint of migration properties, it is preferable to use a reactive curable silicone resin. Reactive curable silicone resins can include those that use addition reactions, condensation reactions, or ultraviolet or electron beam curing. More preferably, low-temperature curable addition reaction resins that can be processed at low temperatures, and ultraviolet or electron beam curing resins are preferred. By using these silicone resins, processing can be done at low temperatures when coating polyester films. Therefore, there is less thermal damage to the polyester film during processing, a polyester film with high flatness can be obtained, and defects such as pinholes can be reduced when manufacturing thin films such as ceramic green sheets.

[0083] Examples of silicone resins used in addition reactions include those obtained by reacting polydimethylsiloxane, which has vinyl groups introduced to its terminals or side chains, with hydrodienesiloxane using a platinum catalyst and curing the reaction. In this case, it is preferable to use a resin that can be cured at 120°C in 30 seconds or less, as this allows for processing at lower temperatures. Examples include low-temperature addition-curing types (LTC1006L, LTC1056L, LTC300B, LTC303E, LTC310, LTC314, LTC350G, LTC450A, LTC371G, LTC750A, LTC755, LTC760A, etc.) and thermal UV-curing types (LTC851, BY24-510, BY24-561, BY24-562, etc.) from Dow Toray, as well as solvent addition + UV-curing types (X62-5040, X62-5065, X62-5072T, KS5508, etc.) and dual-cure curing types (X62-2835, X62-2834, X62-1980, etc.) from Shin-Etsu Chemical Co., Ltd.

[0084] Examples of silicone resins used in condensation reactions include those in which polydimethylsiloxane with OH groups at the ends and polydimethylsiloxane with H groups at the ends are condensed using an organotin catalyst to create a three-dimensional crosslinked structure.

[0085] Examples of UV-curable silicone resins include, as the most basic type, those that utilize the same radical reaction as conventional silicone rubber crosslinking, those that introduce unsaturated groups for photocuring, those that decompose onium salts with UV light to generate strong acids which then cleave epoxy groups for crosslinking, and those that crosslink through the addition reaction of thiols to vinylsiloxane. In addition, electron beams can 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 used include UV-curing silicones from Shin-Etsu Chemical Co., Ltd. (X62-7028A / B, X62-7052, X62-7205, X62-7622, ​​X62-7629, X62-7660, etc.), UV-curing silicones from Momentive Performance Materials Inc. (TPR6502, TPR6501, TPR6500, UV9300, UV9315, XS56-A2982, UV9430, etc.), and UV-curing silicones from Arakawa Chemical Corporation (Silicolise UV POLY200, POLY215, POLY201, KF-UV265AM, etc.).

[0086] As the UV-curing silicone resin mentioned above, acrylate-modified or glycidoxy-modified polydimethylsiloxane can also be used. Good mold release properties can also be obtained by mixing these modified polydimethylsiloxanes with polyfunctional acrylate resins or epoxy resins and using them in the presence of an initiator.

[0087] Other suitable resins for use as release components in release layer molding materials include alkyd resins and acrylic resins having long-chain alkyl groups such as stearyl-modified and lauryl-modified resins, or alkyd resins, acrylic resins, and olefin resins obtained by reactions such as methylated melamine. When molding sheets used in electronic components, silicone-free release agents are also preferred.

[0088] Examples of amino alkyd resins and amino acrylic resins obtained by the reaction of methylated melamine include the Tesfine series manufactured by Showa Denko Materials.

[0089] When using the above-mentioned resin as the release component of the release layer molding material of the present invention, one type may be used, or two or more types may be mixed. When mixing two or more types, two or more silicone-based resins may be used, or it is preferable to mix multiple different resin types, such as a binder resin and a silicone-based resin.

[0090] The laminated film (2) of the present invention can be suitably used as a release film, and in particular when used as a release film when molding thin film sheets such as ceramic green sheets, it is preferable that the release layer does not deform when peeled off, so it is preferable that the release layer is crosslinked and hardened. For this reason, it is also preferable that the release layer contains binder components and crosslinking agents in addition to silicone-based release agents.

[0091] The binder component included in the mold release layer molding material of the present invention preferably consists of a component that can be crosslinked to increase the crosslinking density of the mold release layer and improve the durability and solvent resistance of the mold release layer. Therefore, the binder component is preferably formed by the reaction of a resin having a reactive functional group and a crosslinking agent. It is also preferable that the binder component be formed by self-crosslinking of either the reactive functional group or the crosslinking agent alone. However, the present invention does not exclude embodiments in which the binder component consists only of a resin having a reactive functional group or a crosslinking agent.

[0092] Suitable resins having reactive functional groups include, for example, polyester resins, acrylic resins, polyurethane resins, and polyolefin resins. These resins preferably have at least one reactive functional group selected from carboxyl groups, hydroxyl groups, epoxy groups, amino groups, and the like.

[0093] The release layer molding material of the present invention may also preferably contain a crosslinking agent. Examples of preferred crosslinking agents include melamine-based, isocyanate-based, carbodiimide-based, oxazoline-based, and epoxy-based agents. One or more crosslinking agents may be used in combination. Particularly preferred are crosslinking agents that react with reactive functional groups introduced into the binder component.

[0094] The release layer molding material of the present invention may contain particles with a particle size of 1 μm or less, but from the viewpoint of pinhole generation, it is preferable that it substantially does not contain any particles or other materials that form protrusions.

[0095] The release layer molding material of the present invention may contain additives such as light release additives and heavy release additives, as well as adhesion enhancers and antistatic agents, in order to adjust the release force of the release layer. Furthermore, in order to improve adhesion with the substrate layer, it is preferable to pre-treat the surface of the polylactic acid film with an anchor coat, corona treatment, plasma treatment, atmospheric pressure plasma treatment, etc., before applying the release coating layer.

[0096] In the present invention, the thickness of the release layer can be set according to its intended use and is not particularly limited, but preferably, the thickness of the release layer after curing is in the range of 0.005 to 2.0 μm. A release layer thickness of 0.005 μm or more is preferable because it maintains peeling performance. Furthermore, a release layer thickness of 2.0 μm or less is preferable because the curing time does not become too long, and there is no risk of uneven sheet thickness due to a decrease in the flatness of the release film. In addition, because the curing time does not become too long, there is no risk of the resin constituting the release layer agglomerating and forming protrusions, so it is preferable that pinhole defects in the sheet do not occur easily.

[0097] The outer surface of the film on which the release layer is formed (i.e., the outer surface of the release layer) is preferably flat in order to prevent defects from occurring in the sheet coated and molded on the outer surface of the film. It is preferable that 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. Furthermore, 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 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. If the arithmetic mean roughness of the release layer surface is 10 nm or less and the maximum protrusion height is 200 nm or less, it is preferable that defects such as pinholes do not occur during sheet formation and the yield is good. It can be said that the smaller the arithmetic mean roughness (Sa) of the release layer surface, the better, but it may be 0.1 nm or more, or 0.3 nm or more. It can also be said that the smaller the maximum protrusion height (P), the better, but it may be 1 nm or more, or 3 nm or more.

[0098] The lower limit of the surface free energy of the release layer of the present invention is 8 mJ / m 2 Preferably, it is 10 mJ / m³. More preferably, 10 mJ / m³. 2 That is all. 12 mJ / m 2 The above is even more preferable. 8 mJ / m 2 This is preferable because it reduces the likelihood of the sheet dissolving solution being repelled when applied.

[0099] The upper limit of the surface free energy of the release layer of the present invention is 45 mJ / m 2 Preferably, it is less than 40 mJ / m³. More preferably, 40 mJ / m³. 2 The following is true: 35 mJ / m 2 The following is even more preferable: 45 mJ / m 2 The following is preferable because it provides good peelability of the molded sheet.

[0100] In the present invention, the method for forming the release layer is not particularly limited. A release layer forming material (coating liquid) in which the resin constituting the release component is dissolved or dispersed is applied to one side of a base film, and after removing the solvent by drying, the material is heated, heat-cured, or ultraviolet-cured. In this case, the drying temperature during solvent drying or heat curing is preferably 180°C or lower, more preferably 150°C or lower, and most preferably 120°C or lower. The heating time is preferably 30 seconds or less, and more preferably 20 seconds or less. When the temperature is 180°C or lower, the flatness of the film is maintained, and there is little risk of causing unevenness in the sheet thickness, which is preferable. When the temperature is 120°C or lower, the film can be processed without impairing the flatness of the film, and the risk of causing unevenness in the sheet thickness is further reduced, which is particularly preferable.

[0101] In the present invention, the surface tension of the release layer forming material (coating liquid) when applied to the base film is not particularly limited, but is preferably 30 mN / m or less. By setting the surface tension as described above, the wettability after coating is improved, and the surface irregularities of the coating film after drying can be reduced.

[0102] In the present invention, the release layer forming material (coating liquid) applied to the base film is not particularly limited, but it is preferable to add a solvent with a boiling point of 90°C or higher. Adding a solvent with a boiling point of 90°C or higher prevents bumping during drying, levels the coating film, and improves the smoothness of the coating film surface after drying. The amount of the solvent added is preferably about 10 to 80% by mass of the total coating liquid.

[0103] Examples of application methods for the above-mentioned coating liquid include 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.

[0104] (Release film) The laminated film (2) having a release layer of the present invention can be used for manufacturing and transfer applications of ceramic green sheets, various resin sheets, and optical films, as well as as a release film for adhesive sheets and other adhesive sheets.

[0105] The laminated film (2) having a release layer of the present invention can be applied as a release film, and is particularly suitable as a release film for manufacturing ceramic green sheets. The same applies when the laminated film (1) has a release layer.

[0106] (Ceramic green sheet and ceramic capacitor) Generally, a multilayer ceramic capacitor has a rectangular parallelepiped ceramic body. Inside the ceramic body, first internal electrodes and second internal electrodes are alternately arranged along the thickness direction. The first internal electrodes are exposed on the first end face of the ceramic body. A first external electrode is provided on the first end face. The first internal electrodes are electrically connected to the first external electrode at the first end face. The second internal electrodes are exposed on the second end face of the ceramic body. A second external electrode is provided on the second end face. The second internal electrodes are electrically connected to the second external electrode at the second end face.

[0107] The release film for manufacturing ceramic green sheets is used to manufacture such multilayer ceramic capacitors. For example, it is manufactured 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 a first or second internal electrode is printed on the applied and dried ceramic green sheet. A mother laminate is obtained by appropriately laminating the ceramic green sheet, the ceramic green sheet with the conductive layer for forming the first internal electrode printed on it, and the ceramic green sheet with the conductive layer for forming the second internal electrode printed on it, and pressing them. The mother laminate is divided into multiple parts to produce raw ceramic bodies. Ceramic bodies are obtained by firing the raw ceramic bodies. After that, the multilayer ceramic capacitor can be completed by forming the first and second external electrodes.

[0108] (Laminated film (3)) The adhesive layer of the laminated film (3) described above can be provided on one or both sides of the base film. Preferably, the adhesive layer is provided on the outermost surface of the laminated film (3). Furthermore, the embodiment of the laminated film (3) having the adhesive layer can be applied together with the embodiments of the laminated films (1) and (2). That is, as the base film of the laminated film (3) having the adhesive layer, the biaxially oriented polylactic acid film of the present invention can be used, as well as the laminated film (1). In this case, the adhesive layer can be laminated on either the side of the resin layer or the side of the base film where the resin layer is not laminated, but it is preferable to laminate it on the side of the base film where the resin layer is not laminated.

[0109] Furthermore, when an adhesive layer is applied to the laminated film (2) having the release layer, the adhesive layer may be on one side of the base film, and the release layer may be on the side opposite to the side with the adhesive layer (the back side). Having a release layer on the back side allows the laminated film (3) to be smoothly unwound from the roll even when it is wound into a roll, making it easier to distribute the laminate as a roll.

[0110] A separator may be provided on the adhesive layer of the laminated film (3) to protect the adhesive layer. The separator can be any material that has release properties, for example, a material such as paper or film with the above-mentioned release layer provided. The above-mentioned release layer can be used as the release layer for the separator. One preferred distribution method for the laminated film (3) is to laminate the separators and wind them into a roll.

[0111] (Adhesive layer) The adhesive constituting the adhesive layer is not particularly limited, and one or more known adhesives can be used in combination, such as rubber-based adhesives, acrylic-based adhesives, vinyl alkyl ether-based adhesives, silicone-based adhesives, polyester-based adhesives, polyamide-based adhesives, urethane-based adhesives, styrene-diene block copolymer-based adhesives, or creep-improved adhesives obtained by blending these adhesives with a heat-meltable resin having a melting point of about 200°C or less. The adhesive may be any known adhesive such as solvent-type, emulsion-type, hot-melt-type, energy-ray-curing-type, or heat-peel-type.

[0112] Generally, the adhesives used include rubber-based adhesives using natural rubber or various synthetic rubbers as base polymers; and acrylic adhesives using acrylic polymers (homopolymers or copolymers) as base polymers, which use one or more of the following as monomer components: (meth)acrylate alkyl ester {wherein (meth)acrylate alkyl ester means alkyl acrylate and / or alkyl methacrylate. In this specification, (meth) has the same meaning as above.}. In the present invention, acrylic adhesives using acrylic polymers as base polymers are particularly preferred.

[0113] Examples of alkyl (meth)acrylate esters used as monomer components of the aforementioned acrylic polymers include C1-20 alkyl (meth)acrylate esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

[0114] The acrylic polymer may, if necessary, contain units corresponding to other monomer components copolymerizable with the alkyl (meth)acrylate, for the purpose of modifying properties such as cohesiveness, heat resistance, and crosslinkability. Examples of such monomeric components include (meth)acrylic acid esters having an aliphatic cyclic skeleton such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cyclohexylmethyl (meth)acrylate, and bornyl (meth)acrylate; (meth)acrylic acid esters having an aromatic carbon ring such as phenyl (meth)acrylate and benzyl (meth)acrylate; carboxyl group-containing monomers such as acrylic acid, methacrylic acid, carboxyethyl acrylate, carboxypentyl acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid; acid anhydride group-containing monomers such as maleic anhydride and eicotanoic anhydride; and hydroxyl group-containing monomers such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, hydroxyhexyl (meth)acrylate, hydroxyoctyl (meth)acrylate, hydroxydecyl (meth)acrylate, hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl methacrylate. Monomers; sulfonic acid group-containing monomers such as styrene sulfonic acid, allyl sulfonic acid, 2-(meth)acrylamide-2-methylpropanesulfonic acid, (meth)acrylamidepropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid; (meth)acrylamide-containing monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, and N-methylolpropane(meth)acrylamide; aminoalkyl (meth)acrylate monomers such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; alkoxyalkyl (meth)acrylate monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; maleimide monomers such as N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, and N-phenylmaleimide;Itaconimide monomers such as N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, and N-laurylitaconimide; succinimide monomers such as N-(meth)acryloyloxymethylenesuccinimide, N-(meth)acryloyl-6-oxyhexamethylenesuccinimide, and N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; vinyl acetate, propion Vinyl monomers such as vinyl acid, N-vinylpyrrolidone, methylvinylpyrrolidone, vinylpyridine, vinylpiperidone, vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole, vinylimidazole, vinyloxazole, vinylmorpholine, N-vinyl carboxylic acid amides, styrene, α-methylstyrene, N-vinylcaprolactam; cyano group-containing monomers such as acrylonitrile and methacrylonitrile; epoxy group-containing acrylic monomers such as glycidyl (meth)acrylate; (meth)acrylate Glycol-based acrylic ester monomers such as ethylene glycol, polypropylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, and methoxypolypropylene glycol (meth)acrylate; acrylic ester monomers having heterocycles, halogen atoms, silicon atoms, etc., such as N-(meth)acryloylmorpholine, tetrahydrofurfuryl (meth)acrylate, fluorine (meth)acrylate, and silicone (meth)acrylate; polyfunctional monomers such as hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy acrylate, polyester acrylate, and urethane acrylate; olefin-based monomers such as isoprene, butadiene, and isobutylene;Examples include vinyl ether and other vinyl ether monomers. These monomeric components can be used individually or in combination of two or more.

[0115] Furthermore, it is preferable to use biomass-derived raw materials for the adhesive layer. Methods for using biomass-derived raw materials include using a biomass-derived base polymer and a biomass-derived crosslinking agent, but it is preferable to use a biomass-derived base polymer, and even more preferably to use a biomass-derived crosslinking agent.

[0116] To make synthetic rubber biomass-derived, in addition to using biomass-derived diene monomers such as butadiene and isoprene, biomass-derived styrene may also be used. As a method for making acrylic polymers biomass-derived, it is preferable to use biomass-derived acrylic monomers as monomer components. In the present invention, bioacrylic adhesives with acrylic polymers as the base polymer are particularly preferred.

[0117] The aforementioned acrylic monomer is made from (meth)acrylic acid, and biomass-derived acrylic monomer can be produced by using biomass-derived (meth)acrylic acid as a raw material. When the biomass-derived acrylic monomer is an alkyl (meth)acrylate, there are two methods: one in which the (meth)acrylic acid is derived from biomass, and another in which the alcohols, etc., that react with the carboxyl group of the (meth)acrylic acid are derived from biomass. Either method is acceptable, but it is particularly preferable to use biomass-derived alcohols for both. The (meth)acrylic acid derived from biomass raw materials is not particularly limited; for example, acrylic acid can be produced from biomass-derived raw materials via acrolein from glycerin, a by-product of biodiesel fuel production from vegetable oil. For methacrylic acid, for example, methods such as the one proposed in WO2014 / 038216, which uses microorganisms capable of producing methacrylic acid from organic matter containing isobutyric acid or valine, can be used. Furthermore, various alcohols are known and can be used, including methanol, ethanol, propanol, butanol, pentanol, hexanol, 2-ethylhexanol, and 2-octanol. Additionally, 2-hydroxyethyl (meth)acrylate can be produced using biomass-derived ethylene oxide. Biomass-derived (meth)acrylic acid can also be used as a copolymer component of alkyl (meth)acrylates.

[0118] Acrylic polymers can be produced by known radical polymerization methods such as solution polymerization, bulk polymerization, and emulsion polymerization. Acrylic polymers may be random copolymers, block copolymers, graft polymers, etc. Conventional polymerization initiators and chain transfer agents can be used in polymerization.

[0119] The weight-average molecular weight of the base polymer constituting the adhesive is, for example, 10,000 to 2,000,000, preferably 300,000 to 1,500,000. If the weight-average molecular weight of the base polymer is too low, it will be excellent in terms of conformability to the adherend, but when peeled off by heat, for example, it will be more likely to cause contamination such as adhesive residue on the adherend. On the other hand, if the weight-average molecular weight of the base polymer is too high, it will be more likely to reduce its conformability to the adherend.

[0120] In addition to the base polymer, the adhesive may optionally contain appropriate additives such as crosslinking agents (epoxy crosslinking agents, isocyanate crosslinking agents, melamine crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, metal chelate compounds, etc.), crosslinking accelerators (crosslinking catalysts), tackifiers (e.g., rosin derivative resins, polyterpene resins, petroleum resins, oil-soluble phenolic resins, etc.), thickeners, plasticizers, fillers, foaming agents, anti-aging agents, antioxidants, UV absorbers, antistatic agents, surfactants, leveling agents, colorants, flame retardants, and silane coupling agents.

[0121] The crosslinking agent made from biomass-derived raw materials is not particularly limited. For example, if it is an isocyanate, a crosslinking agent made from biomass-derived raw materials can be produced using 1,5-pentamethylene diisocyanate made from plant-derived raw materials. For example, Mitsui Chemicals sells a commercially available product called Tabio(R) which can be preferably used. In addition, biomass-derived isophorone diisocyanate produced via biomass-derived acetone has been reported by Evonik, and biomass-derived diphenylmethane diisocyanate is also known and can be used as a crosslinking agent.

[0122] For epoxy resins, for example, Green Denacol(R) GEX-313, 512, 521, 622, 614B, and 252 are commercially available from Nagase ChemteX Corporation and can be used. Furthermore, since melamine crosslinking agents are synthesized using urea and carbon dioxide, they produce less carbon dioxide emissions and are therefore preferred as crosslinking agents used in combination with biomass-derived resins. In addition, while melamine crosslinking agents are used as alkyl etherified melamine, those alkyl etherified using bioaldehyde, biomethanol, biobutanol, etc., are preferably used.

[0123] By reacting a (meth)acrylic acid-based alkyl ester made from the biomass-derived raw materials with a crosslinking agent made from the biomass-derived raw materials, an adhesive layer made from biomass-derived raw materials can be produced.

[0124] These adhesives are commercially available, for example, from Toyo Chem Co., Ltd. as the EKX series, including 20-136, -137, -139, -140, -142, etc., and from Daido Chemical Industries Co., Ltd., including P-7360A, P-7360B, P-7361A, P-7361B, P-7366A, P-7366A, P-7369, etc., and these are preferably used.

[0125] The biomass content of the adhesive layer is preferably 5% or more, more preferably 10% or more, even more preferably 20% or more, and particularly preferably 30% or more. A higher biomass content of the adhesive layer is preferable, with an upper limit of 100%, however, it may be difficult to make all additives and other components biomass-derived. Therefore, the biomass content of the adhesive layer may be 95% or less, or even 90% or less. The biomass content of an adhesive can be calculated by determining the proportion of carbon derived from biomass resources by measuring the percentage of C14 contained in the total carbon atoms of the adhesive. This biomass content can be determined, for example, by radiocarbon (C14) measurement as shown in ASTM D6866-16 Method B (AMS). The above value represents the mass of the biomass-derived component (for example, in the case of ethyl acrylate, if the acrylic acid portion is derived from fossil raw materials and the ethanol is biomass-derived, it represents the ratio of the mass of -OC2H5 groups to the mass of ethyl acrylate). However, if the composition of the adhesive is not precisely known, the ratio of biomass-derived carbon to the total carbon (molar ratio) may be used. In the case of a molar ratio, the biomass content is preferably 3.3% or more, more preferably 6.6% or more, even more preferably 13.2% or more, and particularly preferably 20% or more, with the upper limit being the same.

[0126] The adhesive layer can be formed by known or conventional methods. For example, this could involve applying the adhesive composition onto a substrate (or the intermediate layer if one exists on the substrate), or applying the adhesive composition onto a suitable separator to form an adhesive layer, and then transferring (adhering) the adhesive layer onto the substrate (or the intermediate layer if one exists on the substrate). The application can generally be carried out using a coater, extruder, printing press, or the like, which are commonly used for forming adhesive layers.

[0127] The thickness of the adhesive layer can be appropriately selected depending on the application, for example, 2 to 3000 μm, preferably about 5 to 500 μm, but it may also be 200 μm or less, 100 μm or less, or 50 μm or less.

[0128] The adhesive strength of the adhesive layer at 25°C (180° peel, against polyethylene terephthalate film, tensile speed 300 mm / min) can be appropriately selected according to the application (weak adhesive type, strong adhesive type, etc.), for example, 3.0 N / 20 mm or more, preferably 5.0 N / 20 mm or more, more preferably 7.0 N / 20 mm or more, and in the case of the strong adhesive type, more preferably 10.0 N / 20 mm or more.

[0129] The laminated film (3) of the present invention may have other layers (intermediate layers) between the base film and the adhesive layer, if necessary. The intermediate layer may be, for example, an elastic layer, a rigid layer, or the resin layer of the laminated film (1). However, since the laminated film (3) of the present invention is used as an adhesive tape or adhesive sheet, it is preferable that there is no release layer or a similar release layer between the base film and the adhesive layer. For example, it is preferable that when the adhesive layer side of the laminated film (3) of the present invention is attached to a commercially available soda-lime glass plate and peeled off after 5 minutes, the adhesive layer peels off together with the base film.

[0130] The laminated film (3) of the present invention can be used in a variety of applications as an adhesive tape or adhesive sheet. For example, for optical applications, • Protective films for image display devices, image display panels, touch panels, polarizing plates, etc. • Shatterproof film incorporated into image display devices, etc. • Protective film for lenses, prism sheets, etc. As for buildings, structural components, etc., • Laminated glass, decorative sheets for windows and mirrors, infrared and ultraviolet cut films for windows, etc. • Steel plate modification film, film for signs, advertisements, and signage, office use, and other products: • Office tape, sticky note tape, • Labels, price tags, • Packing tape These are some examples. [Examples]

[0131] Next, the effects of the present invention will be explained using examples and comparative examples. First, the evaluation method for characteristic values ​​used in the present invention is shown below.

[0132] [Evaluation Method] (A) below relates to the measurement of the physical properties of a longitudinally uniaxially oriented film used in the manufacturing process of a biaxially oriented polylactic acid film, and (B) below relates to the evaluation in the manufacturing process of a biaxially oriented polylactic acid film. Furthermore, the physical properties of the obtained biaxially oriented polylactic acid film were measured by the methods (1) to (10) below.

[0133] (A) Crystallinity, glass transition temperature, melting point Using a NETZSCH DSC214 measuring device, a 10 mg sample of longitudinally uniaxially oriented film was used, and the heat flux was measured when the temperature was increased from room temperature to 200°C at a rate of 10°C / min. From the obtained heat flux, the heat quantity ΔHca´ at the exothermic peak at (Tc) < 100°C (lowly regular α´ crystal), the heat quantity ΔHca at the exothermic peak at 120°C ≤ (Tc) (highly regular α crystal), and the heat of fusion ΔHm at the endothermic peak at the melting point were determined. Next, using the equilibrium heat of fusion of perfect polylactic acid crystals (93.6 J / g), the degree of crystallinity was calculated using the following formula. Furthermore, the glass transition temperature (Tg) of FY801 resin was determined from the midpoint of the displacement. The melting point (Tm) was determined from the maximum point of the endothermic peak. Crystallinity (%)=(ΔHm-ΔHca´-ΔHca) / 93.6

[0134] (B) Uniformity in the width direction of transverse stretching (TD) The permeability of the film during the transverse (TD) stretching process was evaluated according to the following criteria. Judgment: The film is stable and uniform stretching is possible in the film width direction. Judgment ×: Although the film is stable, it stretches unevenly in the film width direction.

[0135] (1) Mesophase orientation parameters For the surface of the biaxially oriented polylactic acid film, the total internal reflection (ATR) method of Fourier transform infrared spectroscopy (FT-IR) was used to obtain infrared absorption spectra with the longitudinal direction of the film parallel to the direction of incidence of infrared light (Figure 1). The 757 cm⁻¹ of the infrared absorption spectra was then measured. -1 Absorbance A (crystalline mesophase) and 2996 cm⁻¹ -1 The mesophase orientation parameter was calculated by the ratio of absorbance B (internal standard band) at [location]. The specific measurement conditions for the infrared absorption spectrum are as follows: (measurement) • Spectrometer: Fourier transform infrared spectrophotometer (Agilent Technologies Cary670) • Attached device: Single-reflection ATR attachment (SPECAC Golden Gate MKII) • Polarizer: Wire grid, P-polarization • ATR crystal: Diamond ·Incidence angle: 45° • Total number of times: 64 ·Resolution: 4cm -1 • Wave frequency range: 650cm -1 ~4000cm -1 ·Absorbance A: 710cm -1 ~730cm -1 The minimum value between them is 800cm. -1 Approximately 760 cm when the straight line connecting the points is used as the baseline. -1 Peak height ·Absorbance B:2800cm -1 From 3200cm -1 Approximately 3000 cm when the straight line connecting the points is used as the baseline. -1 Peak height ·Calculation formula: Mesophase orientation parameter = absorbance A (757cm -1 ) / absorbance B(2996cm -1 ) If the longitudinal and transverse directions of the film are unknown, the orientation angle can be measured using a microwave molecular orientation system (for example, MOA-8000 manufactured by Oji Instruments Co., Ltd.) and determined accordingly.

[0136] (2) Thickness The thickness of a biaxially oriented polylactic acid film was measured using the TH-104 manufactured by Tester Industries Co., Ltd. The thickness was determined by the average value of three measurements taken at 50 mm intervals in the flow direction at the center of the film.

[0137] (3) Hayes In accordance with JIS-K-7136, the diffuse transmittance (%) and total light transmittance (%) of biaxially oriented polylactic acid film were measured using an NDH-7000-2 turbidimeter manufactured by Nippon Denshoku Industries Co., Ltd., and the haze (%) was calculated using the following formula. Haze (%) = ((Diffuse transmittance / Total light transmittance)) x 100

[0138] (4) Internal haze Using an NDH-5000 turbidimeter manufactured by Nippon Denshoku Industries, Ltd., the haze of a biaxially oriented polylactic acid film was determined. Then, silicone oil (KF-54) manufactured by Shin-Etsu Silicone Co., Ltd. was applied to the back surface of the sample measurement surface (the side opposite to the incident light source) to determine the internal haze of the biaxially oriented polylactic acid film.

[0139] (5) Total light transmittance In accordance with JIS K 7136, the total light transmittance (%) of biaxially oriented polylactic acid film was measured using an NDH-7000 Type 2 turbidimeter manufactured by Nippon Denshoku Industries Co., Ltd.

[0140] (6) Fracture stress The breaking stress of biaxially oriented polylactic acid film was measured in accordance with JIS-C-2318. Samples were prepared by cutting strips of 120 mm in length and 10 mm in width from the film's width direction using a single-edged razor. Next, using a Shimadzu Autograph AG-IS, the strip samples were clamped with a chuck distance of 100 mm and pulled at a speed of 100 mm / min. The breaking strength (MPa) in the longitudinal direction (MD) and the width direction (TD) was determined from the obtained breaking point stress. From the obtained results, the ratio of the breaking stress in the longitudinal direction to the width direction (MD / TD) was calculated.

[0141] (7) Tensile modulus The breaking stress of biaxially oriented polylactic acid film was measured in accordance with JIS-C-7127. Samples were prepared by cutting strips of 120 mm in length and 10 mm in width from the film's width direction using a single-edged razor. Next, the strip samples were clamped with a 100 mm chuck distance using a Shimadzu Autograph AG-IS and pulled at a speed of 100 mm / min to obtain nominal stress-nominal strain curves. Then, the tensile modulus (GPa) in the longitudinal direction (MD) and width direction (TD) was determined from the stress gradient (formula below) in the 1-2% strain region. Tensile modulus (GPa) = stress / strain

[0142] (8) Thermal shrinkage The thermal shrinkage rate of biaxially oriented polylactic acid film was measured in accordance with JIS-C-2318. A sample measuring 10 mm in width and 190 mm in length was cut from the film along its longitudinal direction (MD), and marks were made at 150 mm intervals along the length. The interval between the marks (A) was measured. Next, the film was placed in an oven in a 150°C atmosphere and heated at 150 ± 3°C for 30 minutes under no load. After this, the interval between the marks (B) was measured. The thermal shrinkage rates in the longitudinal direction (MD) and width direction (TD) at 150°C were then calculated using the following formula. Note that the thermal shrinkage rate in the width direction (TD) was calculated based on the width of the sample. Heat shrinkage rate at 150°C (%) = {(AB) / A} × 100

[0143] (9) Coefficient of kinetic friction The coefficient of dynamic friction of biaxially oriented polylactic acid film was measured in accordance with JIS-K-7125. Samples were prepared with a 70 mm wide, 200 mm long side as the front surface and a 50 mm wide, 50 mm long side as the back surface, both in the longitudinal direction of the film. Then, using an AND (A&D) Tensilon universal tester RGT-1210, the coefficient of dynamic friction (μd) was measured by sliding the back surface of the film against the front surface at a load of 4.4 kg and a speed of 200 mm / min.

[0144] (10) Determination of processing characteristics The cutting performance of biaxially oriented polylactic acid film during die-cutting using a rotary cutter die manufactured by Tsukaya Hamono Co., Ltd. was evaluated by sensory assessment. The evaluation criteria were as follows: The occurrence of cracks or breaks during die-cutting can lead to fracture during the slitting process in production, the generation of chips, and, in the case of laminated films, interfacial delamination. If fracture is induced, productivity will decrease, and if chips are induced, it may affect the quality of the film, such as causing defects. Judgment: Excellent: The cut surface was smooth, and there were no cracks or fractures. Judgment: Slight cracks or fissures were observed on the cut surface. Judgment ×: Cracks or fissures were observed on the cut surface.

[0145] The manufacturing process of the biaxially oriented polylactic acid film described in (B) above was evaluated for Examples 1-6 and Comparative Examples 1-4. The results are shown in Table 1. The physical properties of the obtained biaxially oriented polylactic acid film were evaluated for (1) to (4) and (6) to (10) above. The results are shown in Table 2.

[0146] (Example 1) (1) Preparation of polylactic acid resin As the polylactic acid resin, poly-L-lactic acid, brand FY801 (L-lactic acid / D-lactic acid mass ratio of 99 / 1), manufactured by Anhui Fengyuan Group Co., Ltd., was used. The glass transition temperature (Tg) of FY801 resin was 60°C, and the melting point (Tm) was 180°C. As inorganic particles, SYLYSIA310P manufactured by Fuji Silysia Chemical Co., Ltd. was used. 0.5% by mass of SYLYSIA310P (average particle size 2.7 μm) was added to FY801 and pelletized to prepare a lubricant masterbatch raw material with a lubricant concentration of 0.45% by mass. Next, the lubricant masterbatch raw material was dry-blended with FY801 at a concentration of 0.67% to prepare the raw material.

[0147] (2) Production of biaxially oriented polylactic acid film Poly-L-lactic acid (FY801) was dried under reduced pressure at 80°C for 24 hours (1 Torr), and then the dry blend raw material described in (1) above was supplied to an extruder. It was melted at a temperature of 220°C and extruded in a sheet form from the die. The gear pump rotation speed was controlled so that the thickness was approximately 450 μm. Next, the extruded molten resin was cast onto a cooling drum with a surface temperature of 40°C, and cooled and solidified using an electrostatic application method to ensure close contact with the surface of the cooling drum, thereby creating an unstretched film with a thickness of 450 μm.

[0148] The obtained unstretched film was heated to 60°C using a group of heated rolls, then further heated with a focused IR output of 9.0A, and stretched 3.0 times in the longitudinal direction using a group of rolls with different peripheral speeds to produce a longitudinally uniaxially oriented film.

[0149] Next, the obtained longitudinally uniaxially oriented film was guided to a tenter, held with clips, preheated to 75°C, and then transversely stretched. The transverse stretching temperature was 90°C, the transverse stretching ratio was 4.0 times, and heat treatment was performed at 140°C for 12 seconds. Subsequently, a relaxation treatment (140°C, 3%) was performed after transverse stretching to obtain a biaxially oriented polylactic acid film. In Example 1, the transverse stretching temperature was set to 90°C or higher, and the transverse stretching ratio was reduced to 4.0 times. That is, by controlling the excessive orientation during the stretching process, i.e., mesophase orientation, by controlling the stretching temperature and ratio, the appearance of craze was suppressed and internal haze was reduced, resulting in a film with excellent transparency. The physical properties of the film obtained in Example 1 are shown in Table 2.

[0150] (Example 2) In Example 2, a biaxially oriented polylactic acid film was obtained in the same manner as in Example 1, except that the stretching conditions were changed as shown in Table 1. The physical properties of the obtained film in Example 2 are shown in Table 2. In Example 2, by increasing the transverse stretching ratio and further increasing the stretching temperature in the longitudinal direction and the transverse stretching temperature, excessive orientation during the stretching process, i.e., mesophase orientation, was further suppressed, and a film with superior transparency was obtained. As can be seen from the cross-sectional photograph of the film shown in Figure 2, the occurrence of crazing was significantly improved compared to the film of Comparative Example 1 in Figure 3. In addition, as an effect of increasing the transverse stretching ratio, it was possible to reduce the thermal shrinkage rate in the longitudinal direction due to the relaxation of the molecular chains in the longitudinal direction.

[0151] (Example 3) Example 3 was conducted in the same manner as Example 1, except that the stretching conditions shown in Table 1 were changed, to obtain a biaxially oriented polylactic acid film. The physical properties of the film obtained in Example 3 are shown in Table 2. In Example 3, by reducing the stretching ratio in the longitudinal direction, mesophase orientation was further suppressed, and a film with superior transparency was obtained by suppressing orientation at the time of longitudinal stretching, even while containing inorganic particles. Controlling the orientation in the longitudinal direction, as well as the transverse stretching temperature and ratio, is suitable for controlling mesophase orientation and can be a means of achieving the present invention.

[0152] (Example 4) Example 4 was prepared in the same manner as Example 1, except that (1) the preparation of the polylactic acid resin was carried out without using a lubricant masterbatch raw material and the stretching conditions were changed as shown in Table 1, to obtain a biaxially oriented polylactic acid film free of inorganic particles. The physical properties of the film obtained in Example 4 are shown in Table 2. In Example 4, by increasing the transverse stretching temperature and the heat-fixing temperature, mesophase orientation was suppressed and a film with excellent transparency was obtained. Furthermore, by increasing the heat-fixing temperature, the mobility of molecular chains was suppressed by crystallization treatment at high temperatures, and a film with excellent thermal shrinkage rates in the longitudinal and width directions was obtained.

[0153] (Example 5) Example 5 was conducted in the same manner as Example 4, except that the stretching conditions shown in Table 1 were changed, to obtain a biaxially oriented polylactic acid film free of inorganic particles. The physical properties of the film obtained in Example 5 are shown in Table 2. In Example 5, the transverse stretching temperature and stretching ratio were increased compared to Example 4, and by controlling the mesophase orientation by balancing the stretching temperature and ratio, a film with excellent transparency was obtained. Furthermore, by increasing the heat-fixing temperature, the mobility of molecular chains was suppressed by crystallization treatment at high temperatures, and a film with excellent thermal shrinkage rates in the longitudinal and width directions was obtained.

[0154] (Example 6) Example 6 was conducted in the same manner as Examples 4 and 5, except for changing the stretching conditions shown in Table 1, to obtain a biaxially oriented polylactic acid film free of inorganic particles. The physical properties of the film obtained in Example 6 are shown in Table 2. In Example 6, although the stretching temperature was lowered, the stretching ratio was also relatively low, and sufficient transparency was obtained.

[0155] As specifically demonstrated in Examples 1 to 6 above, by controlling the meso orientation by the stretching temperature and magnification, it is possible to obtain a biaxially oriented polylactic acid film that achieves both transparency and processability without compromising strength and heat resistance, has good dimensional stability even at high temperatures, and possesses high transparency suitable for industrial applications. Furthermore, the surface roughness of the biaxially oriented polylactic acid films obtained in Examples 1 to 6 has a maximum protrusion height (P) of 200 nm or less and an arithmetic mean roughness (Sa) of 10 nm or less, making them suitable as base films for release films used in the manufacture of ceramic green sheets.

[0156] (Comparative Examples 1 and 2) Comparative Examples 1 and 2 were obtained in the same manner as in Example 1, except that the stretching conditions shown in Table 1 were changed, to obtain biaxially oriented polylactic acid films containing inorganic particles. The physical properties of the obtained films of Comparative Examples 1 and 2 are shown in Table 2. In Comparative Examples 1 and 2, the mesophase around the crystals formed during longitudinal stretching was not completely unraveled due to the low transverse stretching temperature, and crystallization progressed during transverse stretching due to the high transverse stretching ratio, which in turn promoted the orientation of the mesophase, resulting in an excessively high mesophase orientation. Comparative Example 2 had an even higher stretching ratio, and the stretching uniformity was also disrupted. Furthermore, the inclusion of inorganic particles resulted in significant creasing within the film, severely impairing transparency. Also, the processing characteristics were deteriorated, so it is outside the scope of the present invention. Figure 3 shows a cross-sectional photograph of the film of Comparative Example 1. It can be seen that many creasings have occurred.

[0157] (Comparative Example 3) Comparative Example 3 was prepared in the same manner as Comparative Example 1, except that the stretching conditions shown in Table 1 were changed without using a lubricant masterbatch raw material, to obtain a biaxially oriented polylactic acid film free of inorganic particles. The physical properties of the obtained film of Comparative Example 3 are shown in Table 2. Comparative Example 3, compared to Example 1, does not contain inorganic particles and has a higher stretching ratio, resulting in worsened internal haze. This is because, even at a stretching temperature of 90°C, increasing the stretching ratio leads to increased orientation crystallization during transverse stretching, increasing meso-orientation, and as a result, craze formation occurs, i.e., internal haze and haze worsen, thus it is outside the scope of the present invention. Although the film of Comparative Example 3 is particle-free and therefore less prone to craze formation, craze formation was observed, as can be seen from the cross-sectional photograph shown in Figure 4.

[0158] (Comparative Example 4) Comparative Example 4 was prepared in the same manner as Comparative Example 1, except that the stretching conditions were changed as shown in Table 1, to obtain a biaxially oriented polylactic acid film free of inorganic particles. The physical properties of the obtained film of Comparative Example 4 are shown in Table 2. Comparative Example 4 has a transverse stretching temperature equivalent to that of the example and exhibits excellent transparency, but the low temperature and magnification of the longitudinal uniaxial stretching reduce the degree of crystallinity at the longitudinal uniaxial stretching stage and cause uneven thickness. Furthermore, the temperature rise and force are not uniform during transverse stretching, resulting in non-uniform permeability in the width direction. Therefore, it is unsuitable from the viewpoint of quality and is outside the scope of the present invention.

[0159] As shown above, the films obtained in Comparative Examples 1-4 exhibit significant creasing within the film when inorganic particles are present, resulting in impaired transparency. Representative examples of creasing are shown in Figure 2, which displays SEM cross-sectional images of Example 2 and Comparative Example 1. Furthermore, even with polylactic acid alone, depending on the degree of crystallinity at the time of longitudinal uniaxial stretching and the transverse stretching conditions, the transverse stretching film permeability, transparency, and processing characteristics may not be suitable. These issues can be addressed by controlling the mesophase orientation.

[0160] [Table 1]

[0161] [Table 2]

[0162] [Evaluation Method] For Examples 11-19 and Comparative Examples 11-14, evaluations were performed in the same manufacturing process for biaxially oriented polylactic acid films as in (B) above. The results are shown in Table 3. Furthermore, the physical properties of the laminated film (1) having a resin layer were measured by the methods described in (1) to (8) and (10) above. The coefficient of dynamic friction described in (9) above was measured by the method described in (9') below. In addition, the physical properties described in (11) and (12) below were measured and evaluated. The results are shown in Table 4.

[0163] Regarding the measurement of the physical properties in (1) above, the penetration depth of the measurement light in the total internal reflection (ATR) method of Fourier transform infrared spectroscopy (FT-IR) is 2 to 3 μm. Therefore, even for laminated films (1) having a resin layer, if the thickness of the resin layer is 0.5 μm or less, the biaxially oriented polylactic acid film (base film) can be measured. Furthermore, the physical properties in (2) to (4), (6) to (8), and (10) above will not be affected by the resin layer if the thickness of the resin layer is 0.5 μm or less (or any effect will be limited to measurement error). If the resin layer is too thick to confirm the absorbance peak, the resin layer can be scraped off with a razor or the like before measuring the physical properties described in (1) through (8) and (10) above.

[0164] (9') Coefficient of kinetic friction The coefficient of dynamic friction of a laminated film (1) having a resin layer was measured in accordance with JIS-K-7125. A piece of film measuring 70 mm in width and 200 mm in length was cut out with the longitudinal direction of the film as the length direction (sample A), and sample A was fixed to a table with the side opposite to the resin layer facing upwards. On the other hand, a piece of film measuring 50 mm in width and 50 mm in length was cut out from the same film (sample B), and the side opposite to the resin layer of sample B was attached to a sliding platform (50 mm in width and 50 mm in length). Next, the film surface of sliding platform B was placed on sample A on the table so that the length direction of the film was parallel, and an AND (A&D) Tensilon universal tester RGT-1210 was used as the measuring device. A load of 4.4 kg was applied to the sliding platform, and the sliding platform was slid along the length direction of sample A at a speed of 200 mm / min to measure and determine the coefficient of dynamic friction (μd) between the resin layer surface and the side opposite to the resin layer of the film.

[0165] (11) Surface free energy γs of the resin layer A laminated film (1) having a resin layer was left for 24 hours in an atmosphere of 50% relative humidity. Then, the contact angles of distilled water and diiodomethane were measured one minute after dropping them onto the resin layer using a FACE contact angle meter (Kyowa Interface Chemical Co., Ltd., CA-X type). Five measurements were taken for each sample, and the average of the three measurements (excluding the maximum and minimum values) was used as the contact angle. From the contact angles of distilled water and diiodomethane, the diffusion component γs of the surface free energy was calculated.

[0166] (12) Appearance of the resin layer coating The surface of the laminated film (1) having a resin layer was illuminated with a bromine light (VIDEOLIGHT VLG301 100V 300W, manufactured by LPL) and a fluorescent lamp (Panasonic Palook, FL 15EX-N 15W, 3-wavelength daylight white) at an angle of approximately 10° to 45° relative to the film surface, and the appearance of the resin layer coating was judged by visual observation according to the following criteria. A: Both the bromine light and the fluorescent light showed no unevenness in the coating, no streaks, or defects, resulting in a uniform coating surface. B: Under bromlight, coating irregularities, streaks, and imperfections can be observed, but they are not visible under fluorescent light. C: Both bromite and fluorescent lighting show coating irregularities, streaks, and paint defects. We judged coatings with a coating appearance rank of A or B to be good, and those with a rank of A were judged to be particularly good.

[0167] The method for preparing the aqueous resin used in the resin layer and the preparation of the coating solution for forming the resin layer used in Examples 11-19 and Comparative Examples 11-14 are as follows.

[0168] (1) Preparation of aqueous resin to be used in the resin layer Dimethyl terephthalate (95 parts by mass), dimethyl isophthalate (95 parts by mass), ethylene glycol (35 parts by mass), neopentyl glycol (145 parts by mass), zinc acetate (0.1 parts by mass), and antimony trioxide (0.1 parts by mass) were charged into a reaction vessel in a stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser, and a transesterification reaction was carried out at 180°C for 3 hours. Next, 5-sodium sulfoisophthalic acid (6.0 parts by mass) was added, and an esterification reaction was carried out at 240°C for 1 hour, followed by a polycondensation reaction at 250°C under reduced pressure (10-0.2 mmHg) for 2 hours to obtain copolymer polyester resin (A) with a number average molecular weight of 19,500 and a softening point of 60°C. In a reactor equipped with a stirrer, thermometer, and reflux device, 30 parts by mass of the polyester resin (A) and 15 parts by mass of ethylene glycol n-butyl ether were added and heated at 110°C, and the resin was stirred to dissolve it. After the resin was completely dissolved, 55 parts by mass of water were gradually added to the polyester solution while stirring. After the addition, the liquid was cooled to room temperature while stirring to prepare a milky white aqueous dispersion of polyester resin with a solid content of 30% by mass.

[0169] (2) Preparation of coating liquid (resin layer forming material) for resin layer formation The following coating agents were mixed to create coating solutions A, B, C, and D. (Coating solution A) Water 46.89% by mass Isopropanol 30.00% by mass Polyester resin aqueous dispersion 20.00% by mass MP4540M 0.08% by mass (Manufactured by Nissan Chemical Industries, solid content concentration 40% by mass, average particle size 450 nm) Snowtex ST-XL 3.00% by mass (Manufactured by Nissan Chemical Industries, solid content 30% by mass, average particle size 45 nm) Surfactant 0.03% by mass (Silicone-based, solid content concentration 100% by mass)

[0170] (Coating solution B) Water 52.25% by mass Isopropanol 30.00% by mass Nikazol RX-2035A 13.64% by mass (Acrylic resin aqueous dispersion, manufactured by Nippon Carbide Co., Ltd., solids content 44% by mass) MP4540M 0.08% by mass (Manufactured by Nissan Chemical Industries, solid content concentration 40% by mass, average particle size 450 nm) Snowtex ST-XL 3.00% by mass (Manufactured by Nissan Chemical Industries, solid content 30% by mass, average particle size 45 nm) Surfactant 0.03% by mass (Silicone-based, solid content concentration 100% by mass)

[0171] (Coating solution C) Water 40.80% by mass Isopropanol 30.00% by mass Hydran AP-201 26.09% by mass (Polyurethane resin aqueous dispersion, manufactured by DIC Corporation, solids content 23% by mass) MP4540M 0.08% by mass (Manufactured by Nissan Chemical Industries, solid content concentration 40% by mass, average particle size 450 nm) Snowtex ST-XL 3.00% by mass (Manufactured by Nissan Chemical Industries, solid content 30% by mass, average particle size 45 nm) Surfactant 0.03% by mass (Silicone-based, solid content concentration 100% by mass)

[0172] (Coating solution D) Water 42.89% by mass Isopropanol 30.00% by mass Zaixen L 24.00% by mass (Polyolefin resin aqueous dispersion, manufactured by Sumitomo Seika Co., Ltd., solids content 25% by mass) MP4540M 0.08% by mass (Manufactured by Nissan Chemical Industries, solid content concentration 40% by mass, average particle size 450 nm) Snowtex ST-XL 3.00% by mass (Manufactured by Nissan Chemical Industries, solid content 30% by mass, average particle size 45 nm) Surfactant 0.03% by mass (Silicone-based, solid content concentration 100% by mass)

[0173] (Example 11) In Example 11, the same procedure as in Example 1 was followed, except that after preparing a longitudinally uniaxially oriented film, the amount of coating solution A used for forming the resin layer was applied to one side of the obtained uniaxially oriented film using the fountain bar coating method, adjusting the amount so that the resin layer thickness was 50 nm. Next, the inline-coated longitudinally oriented film was guided to a tenter, held with clips, and preheated to 75°C before transverse stretching. The transverse stretching temperature was 90°C, the transverse stretching ratio was 4.0 times, and heat treatment was performed at 140°C for 12 seconds. Subsequently, a relaxation treatment (140°C, 3%) was performed after transverse stretching to obtain a laminated film (1) having a resin layer. The physical properties of the obtained film of Example 11 are shown in Table 4. In Example 11, similar to Example 1, by controlling the meso orientation, the occurrence of craze was suppressed and internal haze was reduced, resulting in a laminated film (1) having a resin layer with excellent transparency. Furthermore, the coated appearance of the resin layer was particularly good.

[0174] (Examples 12-16 and Comparative Examples 11-14) Examples 12-16 and Comparative Examples 11-14 yielded laminated films (1) having a resin layer in the same manner as in Example 11, except that Example 11 had changes in the presence or absence of lubricant masterbatch raw materials (inorganic particles) and the stretching conditions, as shown in Table 3. The physical properties of the films obtained in Examples 12-16 and Comparative Examples 11-14 are shown in Table 4. The presence or absence of lubricant masterbatch raw materials (inorganic particles) and the stretching conditions in Examples 12-16 are the same as in Examples 1-6 and Comparative Examples 1-4. Examples 12-16, similar to Examples 1-6, demonstrated that by controlling the meso orientation, the occurrence of crazing was suppressed and internal haze was reduced, resulting in the acquisition of laminated films (1) with a resin layer exhibiting excellent transparency. Furthermore, the coated appearance of the resin layer was particularly good. On the other hand, Comparative Examples 11 to 13 showed the same occurrence of crazing as Comparative Examples 1 to 3, and Comparative Example 14, like Comparative Example 4, had a low temperature and magnification for longitudinal uniaxial stretching, resulting in a decrease in crystallinity at the time of longitudinal uniaxial stretching and non-uniform film permeability in the width direction during transverse stretching, making it unsuitable from the viewpoint of quality.

[0175] (Example 17) Example 17 was conducted in the same manner as Examples 14-16, except that coating solution B was used to form the resin layer and the stretching conditions shown in Table 3 were changed, to obtain a laminated film (1) having a resin layer that does not contain inorganic particles. The physical properties of the film obtained in Example 17 are shown in Table 4. In Example 17, although the stretching temperature was lowered, the stretching ratio was also relatively low, and sufficient transparency was obtained.

[0176] (Example 18) Example 18 was conducted in the same manner as Examples 14-17, except that the coating solution C used for forming the resin layer was changed to the stretching conditions shown in Table 3, to obtain a laminated film (1) having a resin layer that does not contain inorganic particles. The physical properties of the film obtained in Example 18 are shown in Table 4. In Example 18, although the stretching temperature was lowered, the stretching ratio was also relatively low, and sufficient transparency was obtained.

[0177] As specifically demonstrated in Examples 11-18 above, by controlling the meso orientation by the stretching temperature and magnification, it is possible to obtain a biaxially oriented polylactic acid film that has both transparency and processability without compromising strength and heat resistance, exhibits good dimensional stability even at high temperatures, and has high transparency suitable for industrial applications. Furthermore, the surface roughness of the laminated film (1) having a resin layer obtained in Examples 11-18, specifically the surface without the resin layer, had a maximum protrusion height (P) of 200 nm or less and an arithmetic mean roughness (Sa) of 10 nm or less, making it suitable as a release film for the manufacture of ceramic green sheets.

[0178] (Example 19) Example 19 was conducted in the same manner as Example 14, except that the conditions were changed to those shown in Table 3, using coating solution D for forming the resin layer, to obtain a laminated film (1) having a resin layer that does not contain inorganic particles. The physical properties of the film obtained in Example 19 are shown in Table 4. In Example 19, it was shown that increasing the transverse stretching temperature and heat setting temperature, as in Example 14, suppressed mesophase orientation and resulted in a film with excellent transparency, but the surface free energy was low and the coating appearance of the resin layer was poor.

[0179] [Table 3]

[0180] [Table 4]

[0181] [Evaluation Method] For Examples 21 to 30, evaluations were performed in the same manufacturing process for biaxially oriented polylactic acid films as in (B) above. The results are shown in Table 6. In addition, the physical properties of the laminated film (1) having a resin layer (containing an antistatic agent) were measured by the methods described in (1) to (8), (9'), and (10) above.

[0182] The resin layer forming coating solutions E to I (resin layer forming materials) used in Examples 21 to 30 were prepared by adding the following antistatic agents to the polyester resin aqueous dispersion, silica particles, water, isopropanol, and silicone-based surfactant (solid content concentration 100% by mass) used in the preparation of coating solution A, and mixing them in the proportions shown in Table 5. Table 5 also shows the amount (mass%) of antistatic agent contained in the resin layer.

[0183] (Ionic conductive type antistatic agent) TB702 (manufactured by Matsumoto Oil & Fat Pharmaceutical Co., Ltd., solid content 50% by mass) (Conductive polymer type antistatic agent) Orgacon ICP1010 (manufactured by Agfa Materials Japan, solids content 1.2% by mass)

[0184] [Table 5]

[0185] (13) Antistatic properties: Surface resistivity of the resin layer Five 5.0 cm squares were cut from the laminated film (1′) to serve as samples. The surface of the resin layer of each of the five samples was measured using a surface resistance meter (Nitto Seiko Analytic, Highresta MCP-HT800) at 23°C and 65% humidity with an applied voltage of 500V, in accordance with JIS K6911, and the average value was taken as the surface resistivity. If this surface resistivity is 1.0 × 10⁻⁶ 14 Materials with a density of Ω / sq or less are considered to have antistatic properties, especially 1.0 × 10⁻⁶. 13 We determined that values ​​of Ω / sq or less were considered to have good antistatic properties.

[0186] <Preparation of a laminated film (1') in which a resin layer containing an antistatic agent is laminated> (Example 21) In Example 21, after preparing a longitudinally uniaxially oriented film as in Example 1, coating solution E, used for forming the resin layer, was then applied to one side of the obtained uniaxially oriented film using the fountain bar coating method to a laminated polylactic acid film at a rate of 5.0 g / m². 2 Aside from adjusting the amount to achieve the desired consistency and then applying it, the procedure was the same as in Example 1. Next, the inline-coated longitudinally oriented film was guided to a tenter, held with clips, and preheated to 75°C before transverse stretching. The transverse stretching temperature was 90°C, the transverse stretching ratio was 4.0 times, and heat treatment was performed at 140°C for 12 seconds. Subsequently, a relaxation treatment (140°C, 3%) was performed after transverse stretching to obtain a laminated film (1') having a resin layer containing an antistatic agent. The physical properties of the obtained film of Example 21 are shown in Table 7. In Example 21, similar to Example 1, by controlling the meso orientation, the occurrence of crazing was suppressed and internal haze was reduced, resulting in a laminated film (1') having a resin layer containing an antistatic agent with excellent transparency. It also possessed sufficient antistatic properties.

[0187] (Examples 22-26) Examples 22 to 26 yielded laminated films (1') having a resin layer containing an antistatic agent, similar to Example 21, except that the presence or absence of lubricant masterbatch raw materials (inorganic particles) and the stretching conditions were changed as shown in Table 6. The physical properties of the films obtained in Examples 22 to 26 are shown in Table 4. The presence or absence of lubricant masterbatch raw materials (inorganic particles) and the stretching conditions in Examples 22-26 are the same as in Examples 1-6 and Comparative Examples 1-4. Examples 22-26, similar to Examples 1-6, demonstrated that by controlling the meso orientation, the formation of crazing was suppressed and internal haze was reduced, resulting in laminated films (1') having a resin layer containing an antistatic agent with excellent transparency. Furthermore, these films also exhibited sufficient antistatic properties.

[0188] (Examples 27-30) The procedure was carried out in the same manner as in Example 21, except that the coating solution E used for forming the resin layer was replaced with the coating solution listed in Table 6, and a laminated film (1') with a resin layer containing an antistatic agent was obtained. It also possessed sufficient antistatic properties.

[0189] [Table 6]

[0190] [Table 7]

[0191] In addition, the laminated films (1) obtained in Examples 11 to 19, in which the resin layers are laminated, do not contain an antistatic agent, so the surface resistivity of the resin layer is 1.0 × 10⁻⁶ in all cases. 15It was greater than Ω / sq.

[0192] <Formation of release layer> On one side of the biaxially oriented polylactic acid film (base film) obtained in Examples 1 to 6, the following coating liquid was applied as a release layer forming agent at a rate of 5.0 g / m². 2 Apply gravure coating to the desired consistency, dry at 100°C for 30 seconds, then irradiate with ultraviolet light (100 mJ / cm²) using an electrodeless lamp (H bulb manufactured by Fusion Co., Ltd.). 2 This process was carried out to obtain a laminated film (2) having a release layer.

[0193] Furthermore, a release layer was formed on the surface opposite to the resin layer of the laminated film (1) having a resin layer obtained in Examples 11-18 and the laminated film (1') having a resin layer obtained in Examples 21-30, in the same manner as described above, to obtain a laminate (resin layer / base film / release layer) that combines the characteristics of the laminated film (2).

[0194] Release layer forming material • Cationic curing siloxane resin KR-470 (manufactured by Shin-Etsu Chemical Co., Ltd., 100% solids content, alicyclic epoxy group-containing siloxane tetrafunctional oligomer): 7.53 parts by mass • Acid generator: Silicolys UV CATA211 (manufactured by Arakawa Chemical Industries, Ltd., solid content concentration 18%): 1.12 parts by mass Methyl ethyl ketone: 54.33 parts by mass • Toluene 18.30 parts by mass • Normal heptane: 18.3 parts by mass

[0195] [Evaluation Method] (14) Surface roughness Using a non-contact surface shape measurement system (VertScan R550H-M100), the arithmetic mean roughness (Sa) and maximum protrusion height (P) were measured as the average surface roughness of the region under the following conditions. For the arithmetic mean roughness (Sa), the average of 5 measurements was adopted, and for the maximum protrusion height (P), the maximum value of 5 measurements was used after excluding the maximum and minimum values ​​from 7 measurements. (Measurement conditions) • Measurement mode: WAVE mode · Objective lens: 10x · 0.5x Tube lens · Measurement area: 936μm × 702μm (Analysis conditions) · Surface correction: Fourth-order correction · Interpolation processing: Complete interpolation

[0196] The surface roughness of the release layer surface of the laminated film (2) having the obtained release layer, or the laminate (resin layer / base film / release layer) combining the aspects of the laminated film (1) or (1´) is such that the maximum protrusion height (P) is 200 nm or less, and the arithmetic mean roughness (Sa) is 10 nm or less, and it was suitably used as a release film for manufacturing a ceramic green sheet.

[0197] <Formation of the adhesive layer> One surface of the biaxially oriented polylactic acid film (base film) obtained in Example 1 was subjected to corona treatment, and the following adhesive coating liquid A was coated on this corona-treated surface and dried at 100 °C to provide an acrylic-based adhesive layer with a thickness of 10 μm, thereby obtaining a laminated film (3) having an adhesive layer. Similarly, a laminated film (3) having an adhesive layer was obtained using the biaxially oriented polylactic acid films obtained in Examples 2 to 6. The laminated film (3) could be used as various surface protection films. In particular, the laminated film (3) having an adhesive layer using the base films of Examples 2 to 6, especially Examples 3 to 6, had low haze and was suitably used for optical applications such as image display devices, image display panels, touch panels, and polarizing plates.

[0198] ≪Adhesive coating liquid A≫ · SK Dyn 1473H (manufactured by Soken Chemical & Engineering Co., Ltd.) 100 parts by mass · Curing agent L-45 (manufactured by Soken Chemical & Engineering Co., Ltd.) 1.0 part by mass<着

[0199] <Formation of the biomass-derived adhesive layer layer> Corona treatment was performed on one side of the biaxially oriented polylactic acid film (base film) obtained in Example 1. The following adhesive coating solution B was applied to this corona-treated surface and dried at 90°C to form an acrylic adhesive layer made of biomass-derived raw materials with a thickness of 20 μm, thereby obtaining a laminated film (3') having a biomass-derived adhesive layer. Similarly, a laminated film (3′) having a biomass-derived adhesive layer was obtained using the biaxially oriented polylactic acid films obtained in Examples 2 to 6.

[0200] ≪Adhesive Coating Liquid B≫ • Biomass adhesive, Olivine BPS6554 (manufactured by Toyo Chem Co., Ltd.), 100 units Biomass content 15%

[0201] Since the laminated films (3) and (3') obtained above use the biaxially oriented polylactic acid film as a base film, when used as adhesive tapes, etc., problems such as cracks and breaks that occur during the manufacturing or processing of adhesive tapes, etc., can be suppressed.

[0202] (15) Assessment of environmental impact Since both the base film and the adhesive layer of the laminated film (3') are made from biomass-derived raw materials, the overall biomass content of the laminated film can be further increased, making a significant contribution to reducing the environmental burden.

[0203] <Formation of release layer> A release layer was formed on the side of the laminated film (3) or (3') having the adhesive layer obtained above, opposite to the side on which the adhesive layer is provided, in the same manner as above, to obtain a laminate (adhesive layer / base film / release layer) that combines the characteristics of the laminated film (2) having a release layer. When the adhesive layer surface and the release layer surface of the resulting laminate (adhesive layer / base film / release layer) were bonded together and then peeled apart, they could be easily separated, and there were no problems even when the laminate was wound into a roll. [Industrial applicability]

[0204] The polylactic acid film and the laminated film (1) having a resin layer of the present invention can be applied to various uses. Furthermore, the laminated film (2) having a release layer of the present invention is suitable as a release film, and is suitably used, for example, as a release film for the manufacture of ceramic green sheets. Furthermore, the laminated film (3) having an adhesive layer of the present invention is suitably used as various adhesive tapes or adhesive sheets.

Claims

[Claim 1] A biaxially oriented polylactic acid film formed from a film-forming material containing polylactic acid, In the spectrum measured by the total internal reflection method of Fourier transform infrared spectroscopy, the mesophase orientation parameter of the polylactic acid film (757 cm⁻¹) -１ / 2996cm -１ A biaxially oriented polylactic acid film having a peak intensity ratio of 4.0 or less.

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