JP2011074140A - Porous film and manufacturing method for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a porous flexible film that is highly flexible and yet is hard to break. <P>SOLUTION: A coating liquid comprising a polymer compound and a solvent is prepared. The liquid is applied to a support. A coating film is formed on the support. The coating liquid is applied so that the solid content per unit area, K (g/m<SP>2</SP>), in the coated film, is at least 0.5 and at most 50.0. The coated film is dried after causing dew condensation on the coated film. Thus, the porous film 10 is obtained. Only one surface 10a of the porous film 10 has formed a plurality of pores 11 thereon. The porous film 10 is composed of the plastic polymer compound. The thickness TA of the porous film 10 and the thickness T1 of the porous part 12 satisfy (1) 0.3&le;TA-T1&le;40.0 and (2) 0.5&le;T1/TA&le;0.95. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a porous film having a plurality of fine pores and a method for producing the same.

  A so-called porous film having a large number of fine pores is promising in the fields of optics, electronics, regenerative medicine, and the like. For example, in the field of regenerative medicine, it is effective as a material for cell culture (see, for example, Patent Document 1). Some of such porous films have a honeycomb structure in which a plurality of holes are densely formed.

  There are two main ways to make a porous film. One is a so-called nanoimprint method in which the uneven shape of the mold is copied to the material for forming the porous structure, and the other is a material for forming the porous structure as proposed in Patent Document 2, for example. This is a so-called condensation method in which the surface of the solution is condensed to form water droplets. A porous film produced by the dew condensation method is called a self-assembled film because of its behavior of forming a fine structure.

  The nanoimprint method includes a thermal nanoimprint method, a UV nanoimprint method, and a cast nanoimprint method. In the thermal nanoimprint method, a film is heated to a glass transition point (Tg) or higher, pressed against the film, cooled to a temperature lower than Tg, and then peeled off to form an uneven shape on the film. It is a method (for example, refer patent document 3). The UV nanoimprint method is a method of forming a concavo-convex shape by pouring a low-viscosity photo-curable resin into a mold having a concavo-convex shape, then irradiating ultraviolet light to cure the resin, and peeling the cured resin from the mold. It is. The cast nanoimprint method is a method in which a polymer solution is applied to a mold in which fine irregularities are formed so as to form a thin film, and after drying this, an adhesive is applied, a support is attached, and the mold is removed. Yes (see, for example, Patent Document 4).

JP 2001-157574 A JP 2002-335949 A International Publication No. 2004/062886 Pamphlet JP 2006-237312 A

  Depending on the application, flexibility is required for the porous film. For example, instead of using a flat film in a flat state, use it in a bent state, or stick it to an object whose surface shape changes, or use optical, electronic, or cell culture. Although it will be in a flat state at the time of use in a place, it may be bent when accommodated in these. Thus, the use of the porous film greatly expands when there is flexibility during use and storage.

  In order to improve the flexibility, a method of increasing the porosity of the porous film can be considered. This method has certain effects for applications where a porous film having a high porosity is preferred. Among the porous films, those having a honeycomb structure have a high porosity, and those having a communication path formed by connecting holes to each other inside the film have a particularly high porosity. Therefore, the honeycomb structure and the communication path formed tend to be softer. However, there is a problem that the porous film having such a high porosity is easily broken when it is bent, repeatedly bent or stretched. As described above, increasing the void ratio can raise the softness to a certain level, but on the other hand, it causes a problem of being easily broken, and both softness and resistance to breakage are compatible. It does not give flexibility. Moreover, since there is a preferable porosity depending on the application, the application of the porous film is limited by the method of improving flexibility by increasing the porosity.

  And when it sees about the conventional manufacturing method in manufacturing a porous film, a thermal nanoimprint method and UV nanoimprint method have a limit in the improvement of a porosity. In other words, since the thermal nanoimprint method is a method of forming irregularities by pressing the mold, and the UV nanoimprint method is a method of hardening the resin poured into the mold and removing it from the mold, the honeycomb structure, particularly the communication path, is Some porous films cannot be made. Therefore, in the thermal nanoimprint method and the UV nanoimprint method, the shape of the porous film that can be manufactured is limited, and the use of the manufactured porous film is limited. In addition, in the thermal nanoimprint method, when the mold is peeled off from the film, it is necessary to cool to a temperature lower than the Tg of the raw material of the film. Therefore, there is a problem that the production efficiency is worse as the raw material having a lower Tg is used.

  In addition, since the cast nanoimprint method is a method of forming irregularities on a film using a mold, there is a limit to the improvement of the porosity as in the case of the thermal nanoimprint method, and the shape of the produced porous film is limited. Furthermore, in the cast nanoimprint method, since the mold is peeled off from the dried film, the film is easily broken during the peeling. And it is easy to tear at the time of peeling, so that the case where a thin film is manufactured and the unevenness | corrugation is formed densely.

  Compared to the nanoimprint method described above, the dew condensation method tends to be easy to produce from a small porosity to a large one. However, it has not yet produced a flexible porous film having both softness and resistance to tearing.

  Then, an object of this invention is to provide the porous film which has the softness and softness, and its manufacturing method.

  The porous film of the present invention includes a porous portion from one film surface having a smooth surface, the other film surface on which a plurality of dents are formed, to a surface passing through each bottom of the dent, and has a thickness TA (unit: μm). And the thickness T1 (unit: μm) of the porous portion satisfy 0.3 ≦ TA−T1 ≦ 40.0 and 0.5 ≦ T1 / TA ≦ 0.95, and are made of a thermoplastic polymer compound. It is characterized by.

  It is preferable that the porosity in the porous portion from the surface passing through the bottom of each of the plurality of depressions to the one film surface is in the range of 0.5 to 0.95. It is preferable that the porous part and the support part including the other film surface and supporting the porous part are made of the same polymer compound. The polymer compound preferably has a glass transition point of −100 ° C. or higher and 60 ° C. or lower.

The method for producing a porous film of the present invention comprises a coating step in which a coating solution in which a thermoplastic polymer compound is dissolved in a solvent is coated on a support to form a coating film, and an atmosphere in the atmosphere on the coating film. A water droplet forming step of forming water droplets by dew condensation, and drying the solvent and water droplets from the coating film to form the coating film on the support as a porous film having a plurality of holes formed therein. In the coating step, the coating solution is applied such that the solid content K (g / m ² ) per 1 m ^{2 of the} coating film is 0.5 or more and 50.0 or less. Features.

  In the water droplet formation step, humidified air is supplied to the atmosphere, and the water droplets are grown to a predetermined size by adjusting at least one of a wind speed, a dew point, and a temperature of the support body of the humidified air. It is preferable. When the specific gravity of the polymer compound is n, it is preferable to grow the water droplets so that the pore diameter is at least K / n.

  A porous film made of a thermoplastic polymer compound is high in which the thickness TA μm and the thickness T1 μm of the porous portion satisfy the conditions of 0.3 ≦ TA−T1 ≦ 40.0 and 0.5 ≦ T1 / TA ≦ 0.95. Expresses softness and resistance to tearing.

Such a porous film is formed by applying a coating solution on a support so that the solid content g / m ² per unit area in the coated film after coating is 0.5 or more and 50.0 or less. Obtained by implementing the law.

It is a top view of the porous film of the 1st thru / or a 3rd embodiment of the present invention. It is the II-II sectional view taken on the line in FIG. 1 about the porous film which concerns on 1st Embodiment. It is the II-II sectional view taken on the line in FIG. 1 about the porous film which concerns on 2nd Embodiment. It is the II-II sectional view taken on the line in FIG. 1 about the porous film which concerns on 3rd Embodiment. It is the schematic of the film manufacturing equipment of 1st Embodiment. It is the schematic of the film manufacturing equipment of 2nd Embodiment. 2 is a table showing conditions and results of Example 1. It is a table | surface which shows the conditions and result of Example 2. FIG.

  As shown in FIGS. 1 and 2, the porous film 10 of the first embodiment of the present invention is a film in which a plurality of holes 11 are formed only on the first film surface 10a and the second film surface 10b is smooth. .

  The porous portion 12 from the first film surface 10a to the surface 10c passing through the bottom point Pb of each hole and the support portion 13 including the second film surface 10b and supporting the porous portion 12 are made of the same material. The porous film 10 has a single layer structure. That is, although the surface 10c is illustrated in FIG. 2, this is only a conceptual boundary, and the porous portion and the support portion are integral and there is no boundary between them. The plurality of holes 11 have a substantially constant shape and size, and the depth (depth of the recess) DP of the holes 11 is also the same. Therefore, in the porous film 10 shown in FIG. 1, the surface 10c is a flat surface.

  Since the plurality of holes 11 are formed, the porous portion 12 has a honeycomb shape as shown in FIG. 1, that is, a honeycomb structure. On the other hand, no hole is formed in the support portion 13. As described above, the porous film 10 has an asymmetric structure with respect to the center in the thickness direction, that is, a structure in which the porous portion 12 and the support portion 13 are different.

  The thickness of the porous film 10 is TA (μm), and the thickness from the surface 10c to the first film surface 10a where the holes are formed (hereinafter referred to as the thickness of the porous portion) is T1 (μm), and the surface 10c. To the second film surface 10b at which the support portion 13 is exposed (hereinafter referred to as support portion thickness) is T2 (μm). In this case, the thickness TA of the porous film 10 is the sum of the porous portion thickness T1 and the support portion thickness T2. When the hole depth DP is equal to each other as in the porous film 10, the hole depth DP matches the porous portion thickness T1.

  The support portion thickness T2 is not less than 0.3 μm and not more than 40.0 μm. More preferably, the support portion thickness T2 is 0.4 μm or more and 20.0 μm or less, and more preferably, the support portion thickness T2 is 0.5 μm or more and 10.0 μm or less. When the support portion thickness T2 is smaller than 0.3 μm, the film is easily broken, and when the support portion thickness T2 is larger than 40.0 μm, the film becomes hard and lacks softness.

  Moreover, the value of T1 / TA is 0.5 or more and 0.95 or less. Preferably, the value of T1 / TA is 0.6 or more and 0.9 or less, and more preferably, the value of T1 / TA is 0.65 or more and 0.85 or less. When the ratio of the porous part thickness T1 to the thickness TA is smaller than 0.5, the film is difficult to bend, and when it is larger than 0.95, the tear resistance is not exhibited.

Regarding the thickness TA and the thickness T1 of the porous film, the porous film 10 has T1 and TA that satisfy all of the following inequalities (A) to (D).
(A); TA ≦ T1 + 40.0
(B); TA ≧ T1 + 0.3
(C); TA ≦ (1 / 0.5) T1
(D); TA ≧ (1 / 0.95) T1
The straight line represented by TA and T1 representing the boundary of inequality (B) is TA = T1 + 0.3. On the other hand, the straight line represented by TA and T1 that represents the boundary of the inequality (C) is TA = (1 / 0.5) T1. The values of T1 and TA at which these straight lines intersect are (T1, TA) = (0.3, 0.6). In the case of inequality (A) and inequality (C), (T1, TA) = (40, 80) in the same manner. In the case of inequality (B) and inequality (D), (T1, TA) = (5.7, 6.0). In the case of inequality (A) and inequality (D), (T1, TA) = (760,800). The holes 11 are formed in the porous film 10 so that the values of T1 and TA are included in the range of a rectangular region surrounded by a straight line connecting these four values.

  The polymer compound that is the raw material of the porous film 10 is referred to as a first polymer compound. The first polymer compound is preferably thermoplastic.

  By having the above configuration, the porous film 10 has flexibility that combines softness and resistance to tearing.

The plurality of holes 11 are formed so that the porosity in the porous portion 12 is in the range of 0.5 to 0.95. The porosity is defined as Va / m when the sum of the volumes of the holes 11 is Va (m ³ ) and the volume of the porous portion 12 is Vb (m ³ ) in a sample sampled from the porous film 10 with an arbitrary size. This is a value obtained by (Va + Vb). (Va + Vb) is the volume of the porous portion 12 when it is assumed that the hole 11 is not formed in the porous portion 12, that is, when the porous portion 12 is assumed to be a smooth surface. A film having a large porosity has a problem that it is easy to break even if the softness is developed as described above. However, according to the present invention, the above-mentioned effect that the flexibility having both softness and resistance to breakage is developed is particularly remarkable when the porosity of the porous portion is in the above range.

  The above effect is more remarkable when the porosity is 0.6 or more and 0.9 or less, and the most remarkable when the porosity is 0.65 or more and 0.85 or less.

  Although the porous film 10 shown in FIG. 2 is an aspect in which the depth DP of each hole 11 is equal to each other, the present invention is not limited to this. That is, the present invention includes an aspect in which the depth DP of the hole 11 is different from each other. Thus, in the case of porous films (not shown) having different depth DPs, the surface 10c is non-planar, and the thickness T1 of the porous portion 12 is non-uniform, but softness and resistance to tearing. The effect of having the combined flexibility is obtained as in the case of the porous film 10. Further, this effect is particularly remarkable when the porosity of the porous portion 12 from the non-planar surface 10c to the first film surface 10a is within the above range. In the case of porous films (not shown) having different depths DP, the largest value among the depths DP of the holes corresponds to the porous part thickness T1.

  The diameter D of the hole 11 of the porous film 10 is larger than the hole diameter AP on the exposed surface of the porous part 12. In the porous film 10, the distance L between the centers of adjacent depressions is larger than the opening diameter AP or the diameter D, and the holes are formed. For example, a porous film (not shown) in which holes are formed so that the depressions are continuous, that is, the distance L between the centers of adjacent depressions is smaller than the opening diameter AP or the diameter D can be provided.

  The first polymer compound is preferably a hydrophobic polymer. In addition to this hydrophobic polymer, an amphiphilic compound may be used. Amphiphilic compounds have both hydrophilicity and lipophilicity. Specifically, they are compounds having hydrophilic and hydrophobic groups, which makes it easier to form water droplets on the exposed surface of the casting membrane. Become.

  The hydrophobic polymer used in combination with the amphiphilic compound is preferably one that dissolves in a water-insoluble solvent, that is, a hydrophobic solvent, such as poly-ε-caprolactone, poly-3-hydroxybutyrate. , Agarose, poly-2-hydroxyethyl acrylate, polysulfone and the like are preferable. Poly- [epsilon] -caprolactone is particularly preferable when biodegradability is required, or in consideration of cost and availability.

  Other examples of hydrophobic polymers when used in combination with amphiphilic compounds include vinyl polymerized polymers (eg, polyethylene, polypropylene, polystyrene, polyacrylate, polymethacrylate, polyacrylamide, polymethacrylamide, polyvinyl chloride, polychloride). Vinylidene chloride, polyvinylidene fluoride, polyhexafluoropropene, polyvinyl ether, polyvinyl carbazole, polyvinyl acetate, polytetrafluoroethylene, etc.), polyester (eg, polyethylene terephthalate, polyethylene naphthalate, polyethylene succinate, polybutylene succinate, poly Lactic acid etc.), polylactone (eg polycaprolactone etc.), polyamide or polyimide (eg nylon or polyamic acid etc.), polyurethane, polyurethane A, polycarbonate, polysulfone, polyether sulfone, polysiloxane derivatives, and the like. These may be homopolymers, copolymers, polymer blends, or polymer alloys from the viewpoints of solubility, optical physical properties, electrical physical properties, strength, elasticity, and the like.

  As the amphiphilic compound used together with the hydrophobic polymer, oligomers and polymers such as dimers and trimers can be used in addition to many commercially available monomers such as surfactants. When both an amphiphilic compound and a hydrophobic polymer are used, the ratio of the weight of the amphiphilic compound to the weight of the hydrophobic polymer is preferably in the range of 0.1% to 20%.

  Since the porous film 10 of the first embodiment is formed from a single coating solution in which the first polymer compound is dissolved in a solvent, the porous portion 12 and the support portion 13 are made of the same material. If the porous part 12 and the support part 13 are the same material, the density of the porous part 12 and the support part 13 is also the same, and the affinity of the porous part 12 and the support part 13 is high. For this reason, compared with the case where the porous layer 22 and the support layer 23 of the porous film 20 of 2nd Embodiment mentioned later are different materials (refer FIG. 3), the part to which the porous part 12 and the support part 13 connect is shown. Strength can be increased.

  The difficulty of tearing the porous film 10 can be evaluated by measuring the elongation at break by a method defined in JIS K6251. In the present invention, “not easily torn” means that the elongation at break of the porous film 10 measured by this method is 50% or more. The elongation at break is preferably 50% or more, more preferably 100% or more, and still more preferably 200% or more. When the elongation at break is 50% or more, the film is difficult to be torn, so that it can be used for the purpose of bending or winding the film.

  The softness of the porous film 10 is evaluated by measuring the stress MPa applied to the porous film 10 when the porous film 10 is stretched 50% by the method defined in JIS K6251. When the porous film 10 is pulled by 50%, the tensile stress applied to the measurement object when the porous film 10 is pulled is preferably smaller than 20 MPa. More preferably, it is smaller than 10 MPa, and further preferably smaller than 5 MPa. If the elongation stress is smaller than 20 MPa, the film is soft, and can be used for bending or winding the film.

  FIG. 3 is a cross-sectional view of the porous film 20 of the second embodiment. A plan view of the porous film 20 is the same as FIG. The porous film 20 is a film having a multilayer structure including a porous layer 22 in which a plurality of holes 21 are formed and a support layer 23 that is disposed on one surface of the porous layer 22 and has a flat exposed surface. . However, the porous film 20 is formed so that the boundary between the porous layer 22 and the support layer 23 is not confirmed. Thereby, the porous film 20 has the softness | flexibility which had softness and the difficulty of being torn.

  The support layer 23 may have a single layer structure, or may have a multilayer structure for the purpose of increasing the thickness. Thereby, it can be set as the porous film of the more suitable thickness according to the use which raises the tearing resistance as the porous film 20 more or makes it harder. Since the aspect of the plurality of holes 21 formed in the porous layer 22 is the same as that of the hole 11 formed in the porous portion 12 of the first embodiment, description thereof is omitted. The hole 21 is not formed in the support layer 23.

  In the case of the second embodiment, the thickness of the porous layer 22 is a porous portion thickness T1 μm, and the thickness of the support layer 23 is a support portion thickness T2 μm. Since the conditions for the support portion thickness are the same as those in the first embodiment, the description thereof is omitted.

  The high molecular compound used as the raw material of the porous layer 22 is the first high molecular compound as in the porous film of the first embodiment. On the other hand, the polymer compound that is a raw material of the support layer 23 is referred to as a second polymer compound. The second polymer compound is particularly preferably the same polymer compound as the first polymer compound. When the second polymer compound is the same polymer compound as the first polymer compound, the bonding force between the porous layer 22 and the support layer 23 is different between the first polymer compound and the second polymer compound. Compared to Since the support layer 23 does not form water droplets, the support layer 23 may have no hydrophilic group. However, when the first polymer compound has a hydrophilic group, the second polymer compound also preferably has a hydrophilic group. This has the effect of further improving the adhesion between the layers.

  Preferred examples of the second polymer compound include thermoplastic elastomers, such as vinyl chloride polymers, olefin polymers, urethane polymers, polyester polymers, nitrile polymers, polyamide polymers, butadiene polymers, and styrene-butadiene polymers. , Styrene-isoprene-based polymers, and the like. Other examples include poly-ε-caprolactone, poly-3-hydroxybutyrate, polysulfone, polyacrylamide, polymethacrylamide, polyvinyl chloride, polyvinylidene chloride, polyvinyl ether, polyvinyl acetate, polyamide or polyimide (e.g. Nylon, polyamic acid, etc.), polyurethane and the like.

  FIG. 4 is a cross-sectional view of the porous film 30 of the third embodiment. A plan view of the porous film 30 is the same as FIG.

  As shown in FIG. 4, unlike the porous film 10 of FIG. 2, the porous film 30 has a porous layer 32 in which a plurality of holes 31 are formed so that adjacent holes 31 stick together. A plurality of holes 31 are laterally penetrating, that is, penetrating along the film surface, thereby forming a communication path 34 communicating in the surface direction. Thus, the porous film 3 has no partition wall between adjacent holes. Thereby, the volume occupied by the holes 31 in the porous film 30 is larger than that of the porous film 10. For this reason, the softness increases while maintaining the resistance to tearing. The communication path 34 is preferably formed by the single layer film of the first embodiment shown in FIG.

  Since the porosity of the porous films 20 and 30, the thickness conditions of the porous films 20 and 30, and the raw material of the porous layer 22 are the same as those of the porous film 10, description thereof is omitted. By satisfying the conditions satisfied by the porous film 10, the porous films 20, 30 have the same effect as the porous film 10.

  Below, the manufacturing method of the porous film 10 is demonstrated. The porous portion is formed by applying a coating solution in which the first polymer compound is dissolved in a solvent.

About a coating liquid, a coating film is formed by apply | coating a coating liquid to a support body so that it may mention later. In the present invention, a coating solution with adjusted solute concentration is prepared while measuring the thickness of the coating film, or a coating solution having a predetermined solute concentration is applied to the support to adjust the thickness of the coating film. To do. Thereby, solid content amount K (g / m < ² >) per unit area in this coating film will be 0.5-50.0. If a porous film is formed using such a coating solution that has a solid content K (g / m ² ), a plurality of holes that do not penetrate from the front surface to the back surface of the film are formed on one surface of the film. can do.

It is more preferable to use a coating solution having a solid content K of the coating film of 0.5 g / m ² or more and 20.0 g / m ² or less, and a coating solution of 0.7 g / m ² or more and 10.0 g / m ² or less. More preferably, a liquid is used. If it is less than 0.5 g / m ^2, the resulting porous film is insufficient is of rupture, easily broken, and those lacking in softness even greater than ² and rupture are of 50.0 g / m Become. Furthermore, if the solid content K is less than 0.5 g / m ² , the film may have a very poor tear resistance penetrating from the surface of the porous portion of the film to the surface of the support portion.

As a method for adjusting the solid content (g / m ² ) per unit area in the coating film, there are a method using the above coating liquid and a method for controlling the thickness of the coating liquid to be applied.

  The solvent used as the solvent for the coating solution is not particularly limited as long as it dissolves the hydrophobic polymer. Examples include chloroform, dichloromethane, carbon tetrachloride, cyclohexane, methyl acetate and the like. By using two or more compounds different from each other as the solvent and appropriately changing the ratio, the formation rate of water droplets, the depth of penetration of water droplets into the casting film, and the like can be controlled.

In order to solid content per unit area of the coating film ^{(m 2) (g / m} 2) is made a coating solution such that the above-mentioned range, by adding a solvent to the coating solution, the solute of the coating liquid The concentration is preferably 0.01% by weight or more and 10% by weight or less. The concentration of the solute in the coating solution is more preferably 0.05% by weight or more and 5% by weight or less. The viscosity η of the coating solution is preferably 1 × 10 ⁻⁴ Pa · s or more and 1 Pa · s or less. The viscosity η of the coating solution is more preferably 1 × 10 ⁻³ Pa · s or more and 1 × 10 ⁻² Pa · s or less.

When the solid content is K (g / m ² ) and the specific gravity of the solute polymer is n (−), the water droplets are grown so that the pore diameter (μm) of the water droplet is at least K / n. It is more preferable. Thereby, although the porosity is as high as 0.5 or more, a flexible porous film having both flexibility and softness can be more reliably produced.

  In the method of controlling the thickness of the coating solution to be applied, the thickness of the coating film immediately after formation is set to 10 μm or more and 2000 μm or less. More preferably, they are 20 micrometers or more and 1500 micrometers or less. More preferably, they are 50 micrometers or more and 1000 micrometers or less. If the thickness is smaller than 10 μm, there is a problem that the coating film is not uniformly formed on the support. If the thickness is 2000 μm or more, a drying time is required and productivity is deteriorated.

  A plurality of pores that do not penetrate from the surface of the porous portion of the film to the surface of the support portion can be formed on one surface of the porous film by the following method using a coating solution that satisfies the above solid content. Accordingly, the thickness TA μm of the porous film and the thickness T1 μm of the porous part satisfy the conditions of 0.3 ≦ (TA−T1) ≦ 40.0 and 0.5 ≦ (T1 / TA) ≦ 0.95. In addition, the dried film is condensed on the coating film so that the porous film has a porosity in the range of 0.5 to 0.95, and the dew point of the humidified air, the temperature of the casting support and the humidification time By adjusting the ratio, the size of water droplets on the coating film can be controlled, and the porosity and the depth of the holes formed in the porous film can be adjusted.

  The method for producing a porous film includes a coating liquid coating process in which a coating liquid is cast on one surface of a casting support, and water droplet formation in which condensation is formed on the coated coating liquid to form water droplets. A water droplet growth step of evaporating the solvent in the coating liquid to grow water droplets, and a water droplet evaporation step of evaporating the water droplets to form a porous layer.

  As a method of applying each coating solution, there are a method of spreading each coating solution on a cast support that has been allowed to stand, and a method of flowing each coating solution from a coating die onto a running casting support. Yes, any method can be used in the present invention. The former is generally suitable for producing a variety of products with a small amount of production, that is, for the production of a small variety of products, and the latter is generally suitable for mass production. In the latter method, a continuous porous film can be formed by continuously flowing out the coating liquid, and the coating liquid can flow out intermittently, that is, the flow from the coating die can be turned on and off in a predetermined time. By repeating, a plurality of porous films having a predetermined length can be manufactured continuously.

  FIG. 5 is a schematic view of a porous film manufacturing facility 41. The application process, the water droplet formation process, the water droplet growth process, and the water droplet evaporation process are all performed in the casting chamber 43. The solvent that has become a gas in the casting chamber 43 is recovered by a recovery device (not shown) and then regenerated by a regeneration device (not shown) provided outside the casting chamber 43 for reuse. The In the present embodiment, an integrated casting in which a first area 46 for application and water droplet formation, a second area 47 for growing water droplets, and a third area 48 for evaporating water droplets are partitioned. Although the chamber 43 is used, each area may be made independent. However, the first area 46 and the second area 47 are preferably provided as close as possible to each other. By passing through the first to third areas 46 to 48 as described above, the coating film 50 is self-organized and becomes the porous film 10 having voids in a predetermined form.

  A casting belt 49 used as a casting support is stretched around rollers 52 and 53, and a casting die 56 is provided above the casting belt 49. At least one of the rollers 52 and 53 is rotated by a driving device (not shown), whereby the casting belt 49 runs continuously. The temperature of the rollers 52 and 53 is adjusted by the temperature controller 54, whereby the temperature of the casting belt 49 that contacts the rollers 52 and 53 is controlled.

  In the first area 46, when the coating liquid 42 flows out from the casting die 56, the coating film 50 is formed on the casting belt 49. A blower intake unit 61 is provided above the traveling path of the coating film 50. The blower / intake unit 61 has a blower port 61a through which humidified air flows out in the vicinity of the coating film 50 and an intake port 61b through which the gas around the coating film 50 is sucked / exhausted, and the temperature, dew point, and humidity of the wind in the blower system. A wind controller (not shown) for independently controlling the wind speed and the suction force in the intake system. The air outlet 61a is provided with a filter for maintaining the dustiness, that is, the cleanliness of the humidified air. A plurality of blower intake units 61 may be provided side by side in the running direction of the casting belt 49.

Here, when the dew point of the wind from the air outlet 61a is TD, the value obtained by TD-TS is ΔT. At least one of the surface temperature TS and the dew point TD is controlled so that ΔT satisfies the following formula (1). The surface temperature TS of the coating film 50 can be measured, for example, by providing non-contact temperature measuring means such as a commercially available infrared thermometer near the coating film 50. If ΔT is less than 1 ° C., water droplets are less likely to be generated, while if ΔT is greater than 30 ° C., water droplets are generated abruptly, resulting in non-uniform water droplet size, There are cases in which they do not line up on a plane but overlap in three dimensions. In the first area 46, ΔT is preferably changed from a large value to a small value. Thereby, the generation speed of the water droplets and the size of the generated water droplets can be controlled, and two-dimensional water droplets having a uniform diameter in the surface direction of the coating film 50 can be formed.
1 ° C ≦ ΔT ≦ 30 ° C (1)

  In the first area 46, the surface temperature TS of the coating film 50 is controlled by a casting belt 49 and a temperature control plate (not shown) arranged to face the casting belt 49. It may be controlled by one side. Further, the dew point TD is controlled by controlling the condition of the humidified air emitted from the blower intake unit 61.

  In the water droplet formation process, humidified air is supplied to the atmosphere, and at least one of the wind speed of the humidified air, the dew point, and the temperature of the support is adjusted to control the generation speed of the water droplets and the size of the generated water droplets. Controlling. As a result, a recess having a depth such that the thickness TA μm and the thickness T1 μm of the porous portion satisfy 0.3 ≦ (TA−T1) ≦ 40.0 and 0.5 ≦ T1 / TA ≦ 0.95 is a porous film. It becomes easy to form only on one side.

In addition, in the water droplet forming step, it is preferable to form water droplets so that the hole diameter is at least K / n. The solid content K (g / m ² ) of the coating film and the specific gravity n (−) of the polymer are known at the stage of forming the coating film. For this reason, the value of K / n can be calculated. Then, for example, the pore diameter of the finally obtained porous film can be measured while measuring the size of the water droplet of the pore diameter with a microscope installed in the first area 46. It is preferable to adjust at least one of the wind speed of the humidified air, the dew point, and the temperature of the support so that the measured pore diameter of the porous film is not less than the value of K / n. Specifically, when the size of the water droplet is increased in order to increase the pore diameter of the porous film, the size of the water droplet can be easily increased by increasing the wind speed and dew point and decreasing the support temperature. In order to reduce the pore size of the porous film, when the size of the water droplet is reduced, the size of the water droplet is easily reduced by lowering the wind speed and the dew point and raising the support temperature.

  In the second area 47, two air intake / intake units 63 and 64 are sequentially arranged along the travel path of the coating film 50. The upstream air intake / intake unit 63 is located immediately downstream of the air intake / intake unit 61 in the first area 46. This is because the water droplets formed in the first area 46 are uniformly grown. The more the first area 46 and the second area 47 are separated from each other, that is, the longer the time from the formation of the water droplet to the entry into the second area 47, the more uneven the size of the water droplet when it has grown. End up. The number of the ventilation intake units is not limited to the number of the present embodiment, that is, 2 and may be 1 or 3 or more. The air intake and intake units 63 and 64 are the same as the air intake and intake unit 61, but are not limited thereto.

In the second area 47, at least one of the surface temperature TS and the dew point TD is controlled so that ΔT satisfies the following formula (2). The surface temperature TS is mainly controlled by a temperature control plate (not shown). This temperature control plate has basically the same structure as the temperature control plate in the first area, and can change the temperature along the running direction of the casting belt 49. The dew point TD is controlled by controlling the condition of the humidified air from the blower port 63a. In the second area 47, the surface temperature TS of the coating film 50 can be measured by providing a temperature measuring means similar to the above in the vicinity of the coating film 50. By setting the conditions of the second area 47 in this way, it is possible to grow water droplets slowly and promote the arrangement of the water droplets by capillary force, so that uniform water droplets can be formed densely. When ΔT is 0 ° C. or less, the growth of water droplets is not sufficient and does not form a dense state, and the shape and size of the holes and the arrangement of the holes in the porous film may be uneven. On the other hand, when ΔT is larger than 10 ° C., water droplets are locally multilayered, that is, formed in a three-dimensional manner, and the shape and size of the holes and the arrangement of the holes in the porous film may be uneven.
0 ° C <ΔT ≦ 10 ° C (2)

  It is preferable to evaporate as much solvent from the coating film 50 as possible while growing water droplets. By setting the surface temperature TS and the dew point TD in the second area 47 within the above ranges, the solvent can be sufficiently evaporated and rapid evaporation can be suppressed. Further, it is preferable to selectively evaporate only the solvent without evaporating the water droplets. Therefore, a solvent having a higher evaporation rate than water droplets under the same temperature and pressure is preferable. This makes it easier for water droplets to enter the coating film 50 as the solvent evaporates.

  In the present invention, the air blowing speed of the humidified air from the air blowing / intake units 61, 63, 64 is 0.02 m / second or more and 10 m / second relative to the moving speed of the coating film 50, that is, the traveling speed of the casting belt 49. The range is preferably in the following range, more preferably in the range of 0.05 m / sec to 5 m / sec, and most preferably in the range of 0.1 m / sec to 2 m / sec. If the relative speed is less than 0.02 m / sec, the coating film 50 may be introduced into the third area 48 (see FIG. 4) before the water droplets are formed in a finely arranged manner. On the other hand, if the relative speed exceeds 10 m / sec, the exposed surface of the coating film 50 may be disturbed or condensation may not sufficiently proceed.

  In the third area 48, four air intake / intake units 71 to 74 are arranged in order along the travel path of the coating film 50. The number of the air intake and intake units is not limited to the number of the present embodiment, that is, 4 and may be 1 or more and 3 or less or 5 or more. The air intake / intake units 71 to 74 are the same as the air intake / intake unit 61, but are not limited thereto.

At least one of the surface temperature TS and the dew point TD is controlled so that the surface temperature TS and the dew point TD satisfy the following formula (3). The surface temperature TS is controlled mainly by the temperature control plate 76. Further, the dew point TD control is performed by controlling the condition of the dry air from the air blowing port 63a. In the third area 48, the surface temperature TS of the coating film 50 can be measured by providing a temperature measuring means similar to the above in the vicinity of the coating film 50. By setting the conditions of the third area 48 in this way, it is possible to stop the growth of water droplets and evaporate them, thereby manufacturing the porous film 10 having uniform pores. When TS ≦ TD, further condensation may occur on the water droplets and the formed porous structure may be destroyed.
TS> TD (3)

  In the third area 48, the main purpose is to evaporate water droplets, but the solvent that could not be evaporated before reaching the third area 48 is also evaporated.

  In the evaporation process of water droplets in the third area 48, a reduced pressure drying device or a so-called 2D nozzle may be used instead of the blower intake units 71 to 74. By performing drying under reduced pressure, it becomes easier to adjust the evaporation rates of the solvent and water droplets, respectively. As a result, the evaporation of the organic solvent and the evaporation of the water droplets can be made better, and the water droplets can be formed better inside the coating film 50. Therefore, the size and shape are controlled at the position where the water droplets are present. Perforations can be formed. The 2D nozzle has an air supply nozzle member that emits air and an exhaust nozzle member that sucks air in the vicinity of the coating film 50. The 2D nozzle is preferably one that can uniformly supply and exhaust air over the entire width of the coating surface. Note that the temperature of the casting belt 49 is preferably gradually increased from the first area 46 to the third area 48. Thereby, the solvent can be efficiently evaporated without controlling the evaporation rate and destroying the porous structure. This temperature increase is preferably performed in the range of 0.005 ° C./second or more and 3 ° C./second or less.

  The film manufacturing equipment 41 further includes a peeling roller 57 that supports the porous film 10 peeled off from the casting belt 49 when the coating film 50 is peeled off from the casting belt 49, and the porous film 10 is sent to the next process. It is done. The next step is, for example, a function providing step for applying various functions to the porous film 10 or a winding step for winding the porous film 10 into a roll.

  FIG. 6 is a schematic view of the production facility 81 for the porous film 20. The manufacturing process of the porous film 30 is omitted because it is the same as the manufacturing process of the porous film 20. Instead of the casting belt 49 (see FIG. 5) used in the production facility 41 for the porous film 10, a supporting film 82 that becomes the supporting layer 23 (see FIG. 3) is used as the casting support. The same members as those of the production facility 81 for the porous film 20 are denoted by the same reference numerals as those for the production facility 41 for the porous film 20.

  The conveyance path of the support film 82 is provided with a plurality of rollers 84 that support the support film 82 on the peripheral surface. Among these rollers 84 are drive rollers, and the support film 82 is rotated by the rotation of these drive rollers. Conveyed continuously. The temperature of the peripheral surface of each roller 84 is independently adjusted by a temperature controller (not shown), and the temperature of the support film 82 is controlled for each area by contacting each roller 84.

  When the coating liquid 42 is applied, the coating surface of the support film 82 and the vicinity thereof are slightly swollen by the coating liquid 42, thereby making it easier to eliminate the boundary between the porous layer and the support film 82. When the first polymer compound that is the raw material of the porous layer and the second polymer compound that is the raw material of the support film 82 are the same polymer, such a boundary is eliminated, and the porous layer and the support film 82 The binding force of is higher than when the first polymer compound and the second polymer compound are different from each other. The process of forming holes in the coating solution is the same as that of the manufacturing equipment 41 for the porous film 10 shown in FIG.

  The film production facility 81 further includes a feeding means (not shown) for sending a long support film 82 wound in a roll shape to the first area 51 and a winding means (not shown) for winding the porous film 20. With. Moreover, it may replace with a winding-up means, and the function provision means for providing another function to the porous film 20 or the processing means which processes the porous film 20 in a predetermined shape may be used.

  By the above manufacturing method, a plurality of uniform hole sizes are formed without increasing the number of steps, and a multilayer film in which the total volume of the holes is controlled with respect to the total volume of the film is manufactured. The

[Experiment 1]
Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

  The porous film 10 was manufactured using the film forming equipment 41 shown in FIG.

A coating solution 42 having the following composition was used.
[composition]
Poly-ε-caprolactone (hereinafter referred to as “PCL”) 0.9 part by weight Amphiphilic polyacrylamide 0.1 part by weight Dichloromethane 99.0 parts by weight

In the first area 46, the coating liquid 42 flows out from the casting die 56 onto the casting belt 49 to form the coating film 50. The thickness of the coating film 50 immediately after the formation was 400 μm. The solid content K (g / m ² ) per unit area contained in the coating film was 4.4. The glass transition point Tg of PCL was −60 ° C.

  The air that was controlled by the air intake unit 61 so that the dew point from the air outlet 61a was 18 ° C. was supplied. The surface temperature of the coating film 50 was controlled to be 10 ° C.

  In the second area 47, the difference ΔT (≈TD−TS) between the surface temperature TS of the coating film and the dew point TD of the blown wind is set to 3 ° C., thereby sufficiently evaporating the solvent and rapidly evaporating. Was suppressed.

  Regarding the blowing speed of the humidified air from the blower intake units 61, 63, 64, the moving speed of the coating film 50, that is, the relative speed with the running speed of the casting belt 49 was set to 0.3 m / sec.

  In the water droplet evaporation process in the third area 48, in order to efficiently evaporate the solvent without controlling the evaporation rate and destroying the porous structure, the temperature increase of the coating film 50 is set to 0.01 ° C./second, The temperature was increased until the temperature of the coating film 50 reached 30 ° C.

  The porous film 10 was obtained by the above process.

[Comparison evaluation]
In order to evaluate the flexibility, in the process of manufacturing the porous film 10 as described above, the composition of the coating liquid applied to the casting belt 49 is changed, and the solid content K, the dew point temperature of each step, and the wind speed are adjusted. Then, as shown in FIG. 7, Experiments 2 to 10 and Comparative Experiments 1 to 6 were performed so as to obtain a porous film 10 having different porosity, thickness TA, porous part thickness T1 and support part thickness (TA-T1). went. And about the porous film 10 obtained by each experiment, the softness | hardness and the difficulty to tear were evaluated. The softness was evaluated by measuring the elongation stress. The resistance to breakage was evaluated by measuring the elongation at break.

[Stretching stress]
The porous film 10 was stretched 50% in an arbitrary direction, and the stress MPa when stretched was measured. And it evaluated on the following references | standards. A indicates that it is soft enough. ○ indicates that it can be bent and used. X indicates that the result cannot be used by bending. The results of each experiment are as described in FIG. -Indicates that, in the evaluation of elongation at break described later, the porous film cannot be stretched by 50%, and the stress during stretching cannot be measured.
◎; Less than 10 MPa ○; 10 MPa or more and less than 20 MPa ×; 20 MPa or more −;

[Elongation at break]
The breaking elongation (unit:%) defined in JIS K6251 was measured. And it evaluated on the following references | standards. A indicates that it cannot be broken in normal use. ○ indicates that it is not easily broken to the extent that it can be used in the field of regenerative medicine. X indicates that the result is not easily broken to the extent that it can be used in the field of regenerative medicine. In addition, the fact that it cannot be stretched by 50% means that it breaks during stretching. The results of each experiment are as described in FIG.
◎; 100% or more ○; 50% or more and less than 100% ×; less than 50%

[Comprehensive evaluation]
Comprehensive evaluation is based on the following criteria. This result is described in the “overall evaluation” column of FIG. The results of each experiment are as described in FIG.
A: Both results of elongation stress and elongation at break are ◎
B: The result of either one of the stress at elongation and the elongation at break is ○
C: The result of either one of the stress at elongation and the elongation at break is x, or
Either the stress at elongation or the elongation at break is not measurable.

  In Experiment 9 in FIG. 7, polycarbonate was used instead of PCL in the coating solution 42. “PC” indicates polycarbonate. In Experiment 10, the porous film 20 (refer FIG. 3) from which the composition of the porous layer 22 and the support layer 23 differs was manufactured using the film forming apparatus 81 shown in FIG. PLLA was used as the support film 82.

  In Experiments 1 to 10, the porous film could be produced without penetrating from the front surface to the back surface of the porous film. In addition, a porous part having a plurality of holes can be formed on one surface of the film, and the thickness TA and the porous part thickness T1 of the porous film are 0.3 ≦ TA−T1 ≦ 40.0 and 0. A porous film satisfying the condition of 5 ≦ T1 / TA ≦ 0.95 could be produced. Evaluation of the stress at elongation and elongation at break for the porous film having such a porosity and thickness gave good results, and it was found that this porous film expresses high softness and resistance to tearing.

  In Experiments 7 and 8, a porous film having a porosity outside the range of 0.5 to 0.95 was produced. Compared to the films obtained in Experiments 5 and 6 that produce a porous film having a porosity in the range of 0.5 to 0.95, the porous films in Experiments 7 and 8 are soft and difficult to break. It turns out that it is a little inferior by evaluation of.

  In Experiment 9, the polymer in the coating solution 42 was polycarbonate. The polycarbonate has a glass transition point of 145 ° C. This temperature is outside the range of −100 ° C. to 60 ° C. The conditions of Experiment 9 except for the type of polymer in the coating solution 42 are the same as those of Experiment 1. Comparing Experiment 9 and Experiment 1, a porous film made of a polymer whose glass transition point is outside the range of −100 ° C. or more and 60 ° C. or less is softer and harder to break than a porous film made of a desired polymer. It turns out that it is a little inferior by evaluation.

  In Experiment 10, a multilayer porous film 20 having different compositions of the porous layer 22 and the support layer 23 was produced. In Experiment 1, a single-layer porous film made of PLLA is produced, and Experiment 10 is the same as that in Experiment 1 except for the composition of the porous film. Comparing Experiment 10 and Experiment 1, it can be seen that the multilayer porous film is slightly inferior in evaluation of softness and resistance to tearing compared to the single-layer porous film.

  In Comparative Experiment 1, a porous film having a supporting portion thickness (TA-T1) smaller than 0.3 and T1 / TA larger than 0.95 was produced. In Comparative Experiment 2, a porous film having a low porosity was produced although the dimensions of (TA-T1) and T1 / TA in Comparative Experiment 1 were the same. In both Comparative Experiments 1 and 2, the porous film could not be stretched by 50%, and neither the softness nor the resistance to tearing could be evaluated. In Comparative Experiment 3, a porous film having a supporting portion thickness (TA-T1) larger than 40.0 and T1 / TA smaller than 0.5 was produced. It can be seen that the evaluation of resistance to tearing is good. However, it turns out that evaluation of softness is not preferable. In Comparative Experiment 4, a porous film having a support thickness (TA-T1) of 40.0 but a T1 / TA smaller than 0.5 was produced. It can be seen that the evaluation of resistance to tearing is good. However, it turns out that evaluation of softness is not preferable.

  In Comparative Experiment 5, the above-described softness and resistance to breakage were evaluated for a porous film having a plurality of holes formed in the thickness direction. Since a plurality of holes are formed in the thickness direction, T1 in the present invention is not determined, and therefore no value is described in the table of FIG. In comparative experiment 6, a through-hole film was produced in the thickness direction. Such a film also has no value in the table of FIG. 7 because T1 in the present invention is not determined. In both Comparative Experiments 5 and 6, the porous film could not be stretched by 50%, and neither the softness nor the difficulty of tearing could be evaluated.

  From the experimental results of Example 1 above, when the thickness TA of the porous film and the thickness T1 of the porous portion are set, the thickness of the support portion (TA-T1) is 0.3 μm or more and 40.0 μm or less, and T1 / It was found that a porous film having a TA of 0.5 or more and 0.95 or less has high flexibility, that is, softness and resistance to tearing.

  The dew point of the wind that is blown to the coating film by the blowing / intake unit 61 while changing the solid content per unit area of the coating film by changing the formulation of the coating liquid in Experiment 1, and the blowing / intake units 61, 63, 64, the relative speed of the running speed of the casting belt 49, the temperature of the support, and the diameter of the holes with respect to the blowing speed of the humidified air from 64 are changed as shown in FIG. Experiments 11 to 15 and Comparative Experiments 7 to 8 were performed by changing the porosity, the thickness TA of the porous film, and the thickness T1 of the porous part. Except these, it experimented on the conditions similar to the experiment 1 of Example 1, and the porous film 10 was produced.

[Comparison evaluation]
According to the experiments 11 to 15 of Example 2, if a porous film is produced using a coating solution in which the solid content K (g / m ² ) per 1 m ² of the coating film is 0.5 or more and 50.0 or less, It was found that a porous film can be produced without penetrating from the front surface to the back surface of the film. In addition, by adjusting the thickness TA and the porous portion T1 of the porous film, a porous portion having a plurality of holes can be formed on one surface of the film, and the thickness TA and the porous portion T1 of the porous film It was also found that a porous film satisfying the conditions of 0.3 ≦ (TA−T1) ≦ 40.0 and 0.5 ≦ (T1 / TA) ≦ 0.95 can be produced.

When a porous film is produced with a coating solution in which the solid content K (g / m ² ) is not 0.5 or more and 50.0 or less, for example, a coating solution in which K (g / m ² ) is 80 is used. If a porous film is produced by using, the thickness TA of the porous film and the porous portion T1 are such that 0.3 ≦ (TA−T1) ≦ 5.0 and 0.5 ≦ (T1 / TA) ≦ 0.95. It turns out that the porous film which satisfy | fills was not able to be manufactured. Further, for example, it was found that if a porous film was produced using a coating solution having K of 0.4 (g / m ² ), a film having holes penetrating in the thickness direction was produced.

DESCRIPTION OF SYMBOLS 10,20,30 Porous film 11,21,31 Hole 12 Porous part 13 Support part 22,32 Porous layer 23,33 Support layer 41 Film manufacturing equipment 61,63,64,71-74 Air intake unit

Claims (7)

One film surface is smooth,
Comprising a porous portion from the other film surface on which a plurality of depressions are formed to a surface passing through each bottom of the depression,
The thickness TA (unit: μm) and the thickness T1 (unit: μm) of the porous portion satisfy 0.3 ≦ TA−T1 ≦ 40.0 and 0.5 ≦ T1 / TA ≦ 0.95,
A porous film comprising a thermoplastic polymer compound.   2. The porous film according to claim 1, wherein a porosity in a porous portion from a surface passing through each bottom portion of the plurality of depressions to the one film surface is in a range of 0.5 to 0.95.   3. The porous film according to claim 2, wherein the porous portion and the support portion that includes the other film surface and supports the porous portion are made of the same polymer compound.   The porous film according to any one of claims 1 to 3, wherein the polymer compound has a glass transition point of -100 ° C or higher and 60 ° C or lower. A coating step in which a coating solution in which a thermoplastic polymer compound is dissolved in a solvent is coated on a support to form a coating film;
A water droplet forming step of forming water droplets by dehydrating moisture in the atmosphere on the coating film;
Drying the solvent and the water droplets from the coating film to form the coating film on the support as a porous film having a plurality of holes,
In the coating step, the coating liquid is applied such that the solid content K (g / m ² ) per 1 m ² area of the coating film is 0.5 or more and 50.0 or less. Production method.   In the water droplet formation step, humidified air is supplied to the atmosphere, and the water droplets are grown to a predetermined size by adjusting at least one of a wind speed, a dew point, and a temperature of the support body of the humidified air. The method for producing a porous film according to claim 5.   The method for producing a porous film according to claim 6, wherein when the specific gravity of the polymer compound is n, the water droplets are grown so that the diameter of the pores is at least K / n.

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