JP5405175B2 - Method for producing porous film - Google Patents

Description

  The present invention relates to a method for producing a porous film having a plurality of holes.

  In the optical field, the electronic field, and the medical field, a large number of micron-scale pores are formed, and a porous film having a honeycomb structure, that is, a honeycomb structure, has been used. Such a porous film contributes to improving the degree of integration, increasing the amount of information, and increasing the definition of image information in the optical and electronic fields, and in the medical field, for example, a culture substrate as a place for cell culture. Used as Among the porous films, those made of a polymer are flexible and have a large degree of freedom in shape when in use, so that they have a wider range of applications.

  As a method for producing a porous film made of a polymer, for example, as in Patent Document 1, a polymer solution in which a polymer is dissolved in a solvent is cast into a liquid film, and moisture in the atmosphere is condensed on the liquid film. There is a method of forming water droplets and evaporating the solvent and water droplets. In such a so-called condensation method, water droplets generated by condensation sink into the liquid film, and the water droplets evaporate to form holes. The polymer film obtained by this method has a very fine honeycomb structure with a pore size of a few μm level.

  Conventionally, a method for producing a porous film has been proposed in the direction of forming pores smaller in order to further refine the structure, but recently, it has been found that there is an optimum size of each hole for each application. Therefore, a porous film in which a plurality of pores having a level of 10 μm to several tens of μm is formed has been desired.

JP 2001-157574 A

  However, the conventional method for producing a porous film including Patent Document 1 cannot form a plurality of holes having a large size of 10 μm to several tens of μm. For example, even if an attempt is made to grow a water droplet large by forming a liquid film relatively thick so as to form a large-sized hole, the growth stops while it is small. As a result, as shown in FIGS. 11 and 12, the obtained film 2 has both the diameter D1 of the hole 3 when projected in the normal direction of the film surface 2a and the opening diameter D2 of the hole 3 in the film surface 2a. It is small enough to be less than 10 μm and the depth of the hole is shallow, and the diameter D1 and the opening diameter D2 of the hole 3 are too small with respect to the center-to-center distance DC between the hole 3 and the hole 3, so that the honeycomb structure is not formed.

  The present inventors considered that the reason why the growth of the water droplets stopped while the water droplets were small was due to some property of the liquid film changing with time during the growth of the water droplets. Therefore, a method is conceivable in which a liquid film is formed with a polymer solution having a lower viscosity so that the inside of the polymer solution does not change until the growth of water droplets sufficiently proceeds. A polymer solution having a low viscosity can be prepared by lowering the polymer concentration. However, with this method, the amount of polymer in the liquid film is too small, for example, neighboring water droplets are connected to each other, and the size of the formed water droplets is too uneven or not a water droplet. A water film may be partially formed. Therefore, even if the solvent and water droplets are evaporated from the liquid film, the film does not become a porous film having a plurality of holes formed uniformly, but becomes a film 6 having uneven unevenness as shown in FIG. . Moreover, since the amount of the solvent that must be evaporated increases as the liquid film has a lower polymer concentration, there is a problem that the load on the environment also increases.

  Furthermore, the larger the water droplet, the thicker the liquid film must be formed. However, the thicker the liquid film, the more the pores that should have been formed by the submerged water droplets cannot be maintained during the evaporation of the water droplets and the solvent, and the porous film having the honeycomb structure cannot be obtained. As shown in FIG. 13, the film 6 has uneven unevenness.

  Accordingly, an object of the present invention is to provide a porous film having a honeycomb structure in which the pore size is uniform, although the diameter is 10 μm to several tens of μm larger than the conventional one.

  The present invention provides a method for producing a porous film in which a plurality of pores are formed on a film surface, a water droplet forming step in which water in the atmosphere is condensed in a solution in which a polymer is dissolved in a solvent to form water droplets; and A solvent evaporation step for evaporating the solvent from the solution so as not to evaporate, a water droplet evaporation step for evaporating water droplets, and a water droplet forming step before the solvent evaporation step so that the solvent does not evaporate from the solution. And a solvent gas supply step for supplying the solvent gas to the substrate.

In the solvent gas supply step, the following (1) or (2) is preferably performed, and in the water droplet formation step, humidified air is preferably supplied onto the solution.
(1) Distributing the solution into the chamber and supplying the solvent gas onto the solution by feeding the solvent gas into the chamber.
(2) Supplying the solvent gas onto the solution by disposing the solution and the liquid to be the solvent gas in the chamber and evaporating the liquid in the chamber.

  According to the method for producing a porous film of the present invention, a porous film having a honeycomb structure with a uniform pore size can be obtained although the diameter is 10 μm to several tens of μm larger than the conventional one.

It is a top view of the porous film by this invention. It is sectional drawing which follows the II-II line of FIG. It is explanatory drawing of the manufacturing process of a porous film. It is the schematic of the liquid film formation method. It is the schematic of the porous film manufacturing apparatus which is the 1st embodiment of this invention. It is sectional drawing which follows the VI-VI line of FIG. It is the schematic of the porous film manufacturing apparatus which is a 2nd embodiment. It is the schematic of the porous film manufacturing apparatus which is a 3rd embodiment. 4 is an optical micrograph of the porous film 10 obtained in Example 7. 2 is an optical micrograph of a porous film obtained in Comparative Example 1. It is a top view of the porous film at the time of using the manufacturing method of the conventional porous film. It is sectional drawing which follows the XII-XII line | wire of FIG. It is sectional drawing of the film at the time of manufacturing by a prior art.

  As shown in FIGS. 1 and 2, the porous film 10 has a plurality of holes 11 formed on one film surface (hereinafter referred to as a first surface) 10 a. As shown in FIG. 2, the hole 11 may be formed as a recess in the first surface 10a without penetrating through the other film surface (hereinafter referred to as the second surface) 10b. In some cases, the first surface 10a penetrates the second surface 10b so as to penetrate in the direction.

  The plurality of holes 11 are formed so as to be distributed in a planar shape along the film surface. The plurality of holes 11 are formed so that the porous film 10 has a honeycomb-shaped so-called honeycomb structure, and may be individually independent as shown in FIG. 2, or may be provided in the direction along the film surface. The adjacent hole 11 and the hole 11 may be independent from each other so that a communication path is formed. When the hole diameter is D1 and the distance between the centers of the adjacent holes 11 and the holes 11 is DC, when the porous film 10 is formed so that D1 <DC, the holes 11 become independent from each other, and D1 ≧ DC When the porous film is made as described above, the plurality of holes 11 become non-independent and a communication path is formed inside.

  The holes 11 have a substantially constant shape and size, and are regularly arranged. Depending on the arrangement and the size of the holes 11, the shape of each opening 11a of the first surface 10a by the holes 11 may be a circle as shown in FIG. 2, or a polygon such as a hexagon. Can be.

  The hole diameter D1 is larger than the diameter of the opening 11a (hereinafter referred to as the opening diameter) D2. D1 and D2 are constant in spite of the large pore diameter D1 and opening diameter D2 compared to the conventional porous film, such as the pore diameter D1 in the range of 1 μm to 120 μm and the opening diameter D2 in the range of 1 μm to 100 μm. It is. The thickness T is in the range of 1 μm to 200 μm.

  According to the present invention, when the volume of the hole 11 is V1, and the volume of the porous film 10 including the volume V1 of the hole 11 is V2, the porosity (%) obtained by 100 × V1 / V2 is 30% or more and 80%. The holes 11 can be formed so as to be in the following range. The volume V2 is equal to the volume in the case where both the first surface 10a and the second surface 10b are flat so-called flat films on the assumption that the pores 11 are not formed in the porous film 10.

  The manufacturing process of the porous film 10 will be described with reference to FIG. The horizontal axis in FIG. 3 indicates time t. As shown in FIG. 3, the porous film 10 is formed with a water droplet forming step 21 in which moisture in the atmosphere is condensed on the liquid surface of the polymer solution in which the polymer is dissolved in a solvent to form water droplets of a desired size. The solvent evaporation step 22 for evaporating the solvent from the polymer solution, the water droplet evaporation step 23 for evaporating the water droplets submerged in the polymer solution, and the solvent contained in the polymer solution do not evaporate so that the generated water droplets are not evaporated as much as possible. And a solvent gas supply step 24 for supplying a solvent gas onto the liquid surface of the polymer solution.

  The water droplet formation step 21 includes a generation step 21a for condensing moisture in the atmosphere on the liquid surface of the polymer solution to generate extremely small water droplets, a growth step 21b for growing the generated water droplets to enlarge them, and a desired size. The arrangement step 21c arranges the plurality of grown water droplets so that they are regularly arranged on the liquid surface of the polymer solution. In FIG. 3, the start time of the generation process 21a (hereinafter referred to as the start of condensation) is P1, the start time of the growth process 21b (hereinafter referred to as the start of growth) is P2, and the start time of the arrangement process 21c (hereinafter referred to as the start of condensation). P3 is referred to as the time when the arrangement starts.

  In FIG. 3, the transition from the generation step 21a to the growth step 21b is shown as shifting at the start of growth P2, but the time boundary between the two steps is not clear, and the growth step 21b starts before the generation step 21a ends. Thus, both the steps 21a and 21b overlap in time. That is, there is a time during which the generation of a very small water droplet and the growth of a water droplet that has already occurred proceed simultaneously. Similarly, the temporal boundary between the growth step 21b and the arrangement step 21c is not clear, and water droplets may continue to grow even after the growth step 21 has shifted to the arrangement step 21c.

  Next, the solvent evaporation step 22 is started. At the start of solvent evaporation P4, the temperature of the polymer solution is raised in order to evaporate the solvent, and thus the water droplet forming step 21 is completed by this temperature rise. However, since it takes some time before the growth of water droplets stops, the timing at which the growth of water droplets actually stops is after P4 at the start of solvent evaporation. Thus, the boundary between the alignment step 21c and the solvent evaporation step 22 is not clear. In this solvent evaporation step 22, the solvent is evaporated to such an extent that the fluidity of the polymer solution is lost. When the fluidity of the polymer solution is lost, the temperature of the polymer solution is raised so that the water droplets evaporate together with the solvent, and the water droplet evaporation step 23 is started. Therefore, the solvent evaporation step 22 is continued after the water droplet evaporation start time P5. And when a water droplet and a solvent evaporate, the porous film 10 will be obtained.

  The solvent gas supplied onto the liquid surface of the polymer solution in the solvent gas supply step 24 performed during the water droplet forming step 21 is the same substance as the solvent contained in the polymer solution. By supplying this as a gas, evaporation of the solvent from the polymer solution is suppressed. However, this is a so-called apparent non-evaporation in which the solvent does not seem to evaporate from the polymer solution, and the solvent gas existing on the liquid surface of the polymer solution and the solvent in the polymer solution need only be in an equilibrium relationship. . That is, it is preferable to maintain the pressure of the solvent gas at the saturated vapor pressure in this way, and the concentration of the solvent gas on the liquid surface is maintained so that the saturated vapor pressure is maintained.

  However, the solvent gas existing on the liquid surface and the solvent in the polymer solution may not have a strict equilibrium relationship. For example, when a new solvent gas cannot be sent from the outside to the atmosphere above the liquid level, the polymer solution is accommodated in a chamber that is partitioned from the external space, and a small amount of the solvent is allowed to evaporate from the polymer solution. By this evaporation, a solvent gas may be present in the atmosphere on the liquid surface. Since the solvent gas is supplied from the polymer solution itself into the atmosphere, a sufficient effect can be obtained even if the above-described equilibrium relationship is not required until the evaporation of the solvent proceeds to some extent. In addition, the solvent gas may be supplied so that the pressure of the solvent gas on the liquid surface (hereinafter referred to as the solvent vapor pressure) is larger than the saturated vapor pressure beyond the equilibrium relationship. If the pressure is higher than the saturated vapor pressure, the solvent gas may condense on the liquid surface of the polymer solution. Therefore, it is preferable that the pressure reaches the saturated vapor pressure.

  By performing the solvent gas supply step 24 until P4 at the start of solvent evaporation, the solvent content in the polymer solution is maintained, so that the viscosity of the polymer solution does not increase until P4 at the start of solvent evaporation. As a result, the growth of water droplets can be further facilitated without stopping, and as a result, the porous film 10 having a larger pore diameter D1 and larger opening diameter D2 than that of the related art can be produced. Furthermore, since the growth of the water droplets proceeds uniformly, a plurality of holes having a uniform shape and size can be formed.

  The solvent gas supply step 24 is most preferably continuously performed during the water droplet formation step 21 up to P4 at the start of solvent evaporation. However, the solvent gas supply step 24 is performed only during the growth step 21a. A porous film 10 having 11 can be produced. Furthermore, when the solvent gas supply step 24 is performed in the arrangement step 21a, the porous film 10 having a more uniform hole shape and a more regular arrangement can be obtained.

  As a method for producing the porous film 10, a method of performing a water droplet forming step 21, a solvent evaporation step 22, a water droplet evaporation step 23, and a solvent gas supply step 24 on a polymer solution put in a container, There is a method in which a water droplet forming step 21, a solvent evaporation step 22, a water droplet evaporation step 23, and a solvent gas supply step 24 are carried out on a liquid film on a support. In the former method, water droplets are generated by condensation on the liquid surface of the polymer solution contained in the container. Thus, the water droplet formation step 21, the solvent evaporation step 22, the water droplet evaporation step 23, and the solvent gas supply step 24 may be performed regardless of the depth and thickness of the polymer solution.

  As shown in FIG. 4, as a method for forming a liquid film 31 made of a polymer solution, the support 32 is moved in one direction indicated by an arrow A, and the polymer solution is formed into a thin film on the moving support 32. There is a casting method of flowing 33. As other methods, when the polymer solution has a relatively low viscosity, the polymer solution is allowed to flow on a stationary support and the wetting and spreading of the polymer solution itself is used. When the viscosity is so high as to be difficult, there is a casting method in which a polymer solution is placed on a support and the polymer solution is spread with a smooth member having a smooth surface, and any method may be used. In addition, while forming this liquid film 31, it is preferable to make the atmosphere around the support body 32 and the polymer solution 33 into the dry atmosphere which suppressed humidity low.

  In the first embodiment for making the liquid film 31 into the porous film 10, the porous film manufacturing apparatus shown in FIGS. 5 and 6 is used. 6 shows only a part of the members shown in FIG. The porous film manufacturing apparatus 41 includes a chamber 42 that houses a support 32 having a liquid film 31 formed on one surface thereof, an air supply unit 43 that feeds air into the chamber 42, and a solvent gas inside the chamber 42. And a solvent gas supply unit 44 for feeding into the gas tank.

  The air supply unit 43 includes a duct 47 that guides air to the chamber 42, a first blower 48 that sends air to the duct 47, and a first temperature that controls the temperature, humidity, and air volume of the air sent by the first blower 48. A controller 49 and a shift mechanism 50 that shifts the duct 47 in the vertical direction are included.

  The solvent gas supply unit 44 includes a duct 53 that guides the solvent gas to the chamber 42, a second blower 54 that sends the solvent gas to the duct 53, and the temperature, humidity, and air volume of the air that is sent out by the second blower 54. And a shift mechanism 56 that shifts the duct 53 in the vertical direction. A plurality of slits 53a extending in the direction along the liquid surface of the liquid film 31 are formed in the duct 53, and the solvent gas flows out from these slits 53a. Similarly, a plurality of slits 47a are formed in the duct 47, and air flows out from each slit 47a.

  The chamber 42 is further provided with a temperature adjusting unit 61 that adjusts the temperature of the support 32 from the lower surface. The temperature adjusting unit 61 is configured to turn on / off temperature rise and temperature lowering of the upper surface in contact with the support 32. A third controller 62 is provided for changing the set temperature.

  An exhaust port 42a for exhaust is formed in the upper portion of the chamber, and its opening / closing and opening degree are adjusted by a valve 24b provided in the exhaust port 24a.

  Using this porous film manufacturing apparatus 41, the porous film 10 is manufactured by the following method. First, the generating step 21 a is started by supplying the humidified air from the duct 43 and supplying the air onto the liquid film 31. At this time, when the temperature of the humidified air is adjusted by the first controller 24 so that the dew point of the atmosphere on the liquid film 31 is higher than the liquid surface temperature of the liquid film 31, water droplets are formed earlier and the generated water droplets. Can be more. Since the liquid film 31 through the support 32 has better temperature responsiveness than the internal atmosphere of the chamber 42, in addition to adjusting the humidity of the air from the duct 43, the temperature adjustment unit 61 allows the support 32 to be adjusted. The temperature of the liquid film 31 may be lowered via

  The water droplets 25 at the time of occurrence are extremely small and each one cannot be recognized with the naked eye, and the size is about several nm to several tens of nm. Next, the growth step 21b is performed to enlarge such extremely small water droplets. In the growth step 21b, the supply of humidified air from the duct 47 is continued.

  In the growth process 21 b, the solvent gas supply process 24 is performed by flowing the solvent gas out of the duct 53 and supplying it onto the liquid film 31. The solvent gas may be guided to the chamber 42 while being mixed with air. In the conventional manufacturing method, the growth of water droplets is suppressed, and eventually the growth stops and the size does not change. However, according to the present invention for supplying the solvent gas, the viscosity on the exposed surface of the liquid film 31 increases. Not to do. Thereby, water droplets can be grown to a desired size. This is because an increase in viscosity on the exposed surface of the liquid film 31 is suppressed by supplying the solvent gas. Thus, in the present invention, the solvent gas is supplied so as to suppress the increase in the viscosity of the exposed surface of the liquid film 31 in particular, so that water droplets can be grown to a desired size. By making water droplets grow larger, the porous film 10 having a larger pore diameter D1 and opening diameter D2 can be obtained.

  The duct 47 and the duct 53 are provided near the inner wall surfaces of the chamber 42 facing each other so that the humidified air and the solvent gas are mixed above the liquid film 31 disposed at the center of the bottom of the chamber 42. The heights of the slit 47a and the slit 53a can be changed independently by the shift mechanisms 50 and 56. Thus, the speed of water droplet growth can be changed by changing the relative positions of the slit 47a and the slit 53a in the vertical direction without adjusting the temperature conditions of the humidified air and the solvent gas, the wind speed, and the like. Can do. By changing the growth speed of the water droplets, the final size of the water droplets can be easily adjusted, and the control of the hole diameter D1 and the opening diameter D2 is facilitated. In addition, by changing the relative positions of the slit 47a and the slit 53a in the vertical direction, the mixing ratio of the humidified air and the solvent gas at the exposed surface of the liquid film 31 and in the vicinity thereof is determined by the air volume of the humidified air and the solvent gas. Can be changed without changing.

  Next, the arranging step 21c is performed. In this arrangement process, water droplets are attracted by capillary force. Thereby, a plurality of water droplets are more densely arranged on the liquid surface of the liquid film 31. In this arrangement step 21c, it is possible to further promote the attraction of water droplets by applying air vibration.

  It is preferable to supply the solvent gas from the duct 53 also during the arranging step 21c. As a result, even when the water droplets are densely arranged, the individual water droplets are not deformed or combined with each other, and are regularly arranged on the liquid surface while maintaining a uniform size.

  In the solvent gas supply step 24 described above, the surface temperature TS of the liquid film 31 is preferably in the range of −5 ° C. to 30 ° C., and the dew point TD of the atmosphere is preferably in the range of 5 ° C. to 30 ° C. It is preferable that the dew point TD of the atmosphere is higher than the surface temperature TS. Both the temperature TA of the humidified air sent to the chamber 42 and the temperature TG of the solvent gas are preferably in the range of 5 ° C. to 30 ° C., and the pressure of the solvent gas in the atmosphere of the chamber 42 is 0.01 MPa or more and 0 It is preferably in the range of 1 MPa or less.

  When the water droplets are regularly arranged, the supply of the solvent gas from the duct 53 is stopped, and the dry air whose humidity is lower than the air in the water droplet forming step 21 is guided from the duct 47 to the chamber 42. Then, the exhaust port 42a is opened to reduce the humidity of the internal atmosphere of the chamber 42. Thus, the solvent is evaporated from the liquid film 31 by supplying dry air and reducing the humidity. The temperature of the supplied dry air is preferably kept as low as possible in order to suppress evaporation of water droplets. Moreover, although the temperature of the liquid film 31 is made higher than that of the water droplet forming step 21 by the third controller 62, the temperature is made low enough to prevent evaporation of the water droplets.

  As the solvent evaporates, the viscosity of the polymer solution constituting the liquid film 31 increases. Then, when the fluidity of the liquid film 31 is lost, the water droplets start to evaporate. The disappearance of the fluidity of the liquid film 31 can be confirmed by visually observing the liquid film 31 and confirming that the degree of cloudiness on the surface of the liquid film 31 does not change.

  In order to positively evaporate water droplets in addition to the solvent, the temperature of the dry air from the duct 47 is set higher than that in the solvent evaporation step 22, and the temperature of the liquid film 31 is also set by the third controller 62 in the solvent evaporation step. Higher than in 22. During the water droplet evaporation process 23, as in the solvent evaporation process 22, the supply of the solvent from the duct 53 is stopped and the exhaust from the exhaust port 42a is performed.

  As described above, the water droplets and the solvent are evaporated to obtain the porous film 10, but the porous film 10 can be manufactured by other methods. For example, you may use the porous film manufacturing apparatus as shown in FIG. Similar to the porous film manufacturing apparatus 41, the porous film manufacturing apparatus 71 as the second embodiment includes an air supply unit 43 and a temperature adjustment unit 61 in the chamber 72. Further, the porous film manufacturing apparatus 71 is provided with a temperature adjusting unit 76 for adjusting the temperature of the container 73 from below in order to heat and evaporate the solvent 74 in the container 73 to form a solvent gas. The unit 76 includes a fourth controller 77 that turns on and off the temperature rise and temperature drop on the upper surface in contact with the container 73 and changes the set temperature.

  When the porous film is manufactured by the porous film manufacturing apparatus 71, the solvent gas is supplied by heating and evaporating the solvent 74. Due to this evaporation, the solvent gas spreads inside the chamber 72, and the solvent gas is supplied onto the liquid film 31. Instead of the container 73 containing the solvent 74, a large number of voids may be formed so as to increase the surface area, and for example, an elastic polymer foam in which a solvent is contained in the voids may be used.

  It is preferable that a plurality of the temperature adjusting units 76 are disposed so as to surround the temperature adjusting unit 61, thereby shortening the time until the solvent gas on the liquid film 31 reaches the saturated vapor pressure and increasing the growth rate of the water droplets. In addition, water droplets can be regularly arranged on the liquid surface while maintaining a uniform size.

  Further, a shift mechanism (not shown) is provided in the upper plate 72c that partitions the interior of the chamber 72 from the upper space. By shifting the upper plate 72c downward by this shift mechanism, the solvent gas is allowed to enter the chamber 72. Can be charged quickly. Further, when the internal volume of the chamber 72 is reduced by displacing the upper plate 72c so as to approach the vicinity of the liquid film 31, the container 73 containing the solvent 74 is not disposed inside the chamber 72. By allowing the solvent in the liquid film 31 to evaporate to some extent, the concentration of the solvent gas in the vicinity of the liquid film 31 is increased, and the pressure of the solvent gas in the atmosphere inside the chamber 72 is maintained near the saturated vapor pressure. Will be able to. That is, in this case, a certain amount of solvent is allowed to evaporate from the liquid film 31, and thereby, the solvent gas is supplied onto the liquid film 31. The supply of the solvent gas is performed until the concentration of the solvent gas on the liquid film 31 becomes a concentration at which the solvent does not evaporate from the liquid film 31. When the concentration of the solvent gas increases to that extent, the concentration of the solvent gas is maintained so that the solvent does not evaporate from the liquid film 31 thereafter. Thus, the supply of the solvent gas in the present invention is not necessarily limited to the supply from the outside, and includes the supply of the solvent gas from the liquid film 31 itself. By shifting the upper plate 72c upward during the solvent evaporation process, the solvent can be evaporated more quickly.

  The porous film manufacturing apparatus 81 of FIG. 8 which is the third embodiment includes a temperature adjusting unit 61 in the chamber 82 as in the case of the porous film manufacturing apparatuses 24 and 71, and an exhaust gas is disposed above the chamber 82. The opening and closing and the opening degree of the exhaust port 82a are adjusted by a valve 82b provided in the exhaust port 82a in which the port 82a is formed.

  The porous film manufacturing apparatus 81 further includes a mixed gas supply unit 83 that supplies a mixed gas of solvent gas and water vapor to the chamber. The mixed gas supply unit 83 includes a duct 87 that guides a mixed gas of solvent gas and water vapor to the chamber 82, and a mixed gas generation unit 88 that produces a mixed gas of solvent gas and water vapor and comes to the duct 87. The duct 87 is formed with a slit 87a through which the mixed gas flows out. The mixed gas generation unit 88 includes a humidifier 91 for generating humidified air, a third blower 92 for sending air to the humidifier 91, a solvent gas generator 93 for generating solvent gas, and the solvent gas. A fourth blower 94 for sending air to the generator 93, and a mixer for mixing the humidified air guided from the humidifier 91 and the solvent gas from the solvent gas generator 93 to produce a mixed gas of water vapor and solvent gas 95.

  The humidifier 91 includes a water tank 97 in which water 96 is stored, and the solvent gas generator 93 includes a liquid tank 102 in which a liquid solvent 74 that becomes a solvent gas is stored. The mixed gas generation unit 88 includes a first pipe 104 that guides air from the third blower 92 to either the water 96 or the mixer 95, and a fourth blower 94 in the solvent 74. The second pipe 106 that guides the air from the pipe, the third pipe 107 that connects the solvent gas generator 93 and the mixer 95, and the mixer 95 and the duct 87 are connected to guide the mixed gas to the duct 87. And a fourth tube 108.

  The first pipe 104 includes a first branch pipe 104a that guides air from the third blower 92 to the water tank 97, and the first valve V1 is provided at a branch position where the first branch pipe 104a branches from the first pipe 104. Is provided. The downstream end of the first branch pipe 104 is disposed in the water 96. The flow path is switched by the first valve V <b> 1 so that air is sent to either the mixer 95 or the water tank 97. Further, on the downstream side of the first branch pipe 104a of the first pipe 104, there is provided a second branch pipe 104b whose downstream end is disposed in the liquid surface of the water 96 in the water tank 97, that is, in a space above the water surface. It is. A second valve V2 is provided at a branch position where the second branch pipe 104b branches from the first pipe 104. By this second valve, switching between guiding the air of the third blower 92 to the mixer 95 without sending it into the water tank 97 and guiding the humid air in the upper space of the water tank 97 to the mixer 95 is performed. .

  One of dry air and humidified air is selectively sent from the third blower 92 to the mixer 95. When sending dry air to the mixer 95, the first valve V1 and the second valve V2 guide the air from the third blower 92 directly to the mixer 95 without going through the water tank 91. When the humidified air is sent to the mixer 95, the flow path is switched by the first and second valves V1 and V2, and the air from the third blower 92 is placed in the water 96 to perform so-called bubbling. . In this way, air with an increased water vapor concentration accumulates in the space above the water surface and guides the humidified air to the mixer 95. Note that the dew point of water vapor in the space above the water surface can be changed by changing the temperature of the water 96. Thereby, the water vapor | steam density | concentration in the humidified air which comes to the mixer 95 can be changed. As described above, the feeding of the dry air and the humidified air whose dew point is controlled to the mixer 95 is switched at a predetermined timing.

  The second pipe 106 has an upstream end connected to the fourth blower 94 and a downstream end arranged lower than the liquid level of the solvent 74. Thereby, the air from the 4th air blower 94 is put in the solvent 74, and bubbling is implemented. In this way, a solvent gas is generated and included in the air. The air containing the solvent gas accumulates in the space above the liquid surface of the solvent 74. At this time, the dew point of the solvent gas in the space above the liquid level can be changed by changing the temperature of the solvent 74. Thereby, the density | concentration of the solvent gas which comes to the mixer 95 can be changed.

  The third pipe 107 has an upstream end disposed on the liquid surface in the liquid tank 102 and a downstream end connected to the mixer 95. Thereby, the air containing the solvent gas of the solvent gas generator 93 is guided to the mixer 95. The solvent gas may be guided to the mixer 95 in a state of being included in the air, or depending on the type of the solvent 74, this may absorb air components and only the solvent gas may be guided to the mixer 95. In some cases, a mixture of a solvent gas and a partial component of air is guided to the mixer 95.

  The third blower 92 has a fifth controller 108 that controls the amount of air sent to the humidifier 91 or the mixer 95, and the fourth blower 94 has a sixth controller that controls the amount of air sent to the solvent gas generator 93. Each controller 110 is provided. When the air from the third blower 92 is guided to the water tank 97 and the humidified air is sent to the mixer 95, the water vapor in the mixed gas in the mixer 95 is controlled by the respective air volume controls of the fifth controller 108 and the sixth controller 110. The ratio with the solvent gas can be controlled. Note that when air is blown from one of the third blower 92 and the fourth blower 94, only one of humidified air, dry air, and solvent gas can be sent to the chamber 82.

  The ratio between the water vapor and the solvent gas in the mixed gas of the mixer 95 can be adjusted by controlling the temperature of the water 96 and the solvent 74 or by controlling the internal temperature of the mixer 95. By controlling the temperature of the water 96 and the temperature of the solvent 74, the dew point of the space of each tank 97, 102 can be controlled, and by controlling the internal temperature of the mixer 95, either the solvent gas or water vapor can be controlled. It is because one side can be condensed.

  The fourth pipe 108 has an upstream end connected to the mixer 95 and a downstream end connected to the duct 87. As a result, the mixed gas from the mixer 95 is discharged from the slit 87 a of the duct 87 into the chamber 82. In this manner, the atmosphere of the chamber 82 includes both humidified air, that is, air containing water vapor and solvent gas.

  The duct 87 has a shift mechanism 109 that shifts the duct 87 in the vertical direction, like the ducts 47 and 53.

  According to this porous film manufacturing apparatus 81, solvent gas and humidified air can be sent as reliably and easily as the porous film manufacturing apparatuses 24 and 71, so that water droplets can be easily and effectively grown. Can do.

  The water tank 97 includes a first temperature controller (not shown) that adjusts the temperature of the water 96 and a second temperature controller (not shown) that adjusts the temperature of the upper space above the water surface. And a fourth temperature controller (not shown) for adjusting the temperature of the upper space above the liquid level. The first pipe 104 and the third pipe 107 are also provided with fifth and sixth temperature controllers (both not shown) for controlling the temperature inside the pipe, respectively, and the mixer 95 is also provided with a seventh temperature controller. . The dew point of water vapor and solvent gas can be controlled as described above by the first and third temperature controllers, and the temperature of water vapor and solvent gas can be adjusted by the second, fourth, fifth and sixth controllers. Thus, the temperature of the mixed gas is adjusted. When the dry air is fed to the mixer 95, the fifth controller controls the temperature of the dry air. In addition to adjusting the temperature of the mixed gas by the seventh controller, the ratio of the water vapor to the solvent gas in the mixed gas can also be changed as described above.

  In the third embodiment, when humidified air is sent to the mixer 95, the humidifier 91 and the solvent gas generator 93 are connected to the mixer 95, respectively. Instead, the humidifier 91 and the solvent gas are connected. It may be arranged in series with the generator 93 and connected to the solvent gas generator 93 and the chamber 82. For example, a solvent gas generator 93 is disposed downstream of the humidifier 91, and the solvent gas generator 93 is connected to the mixer 95. In this case, air from the third blower 92 is humidified by the humidifier 91 to produce humidified air, and a solvent gas is added to the humidified air by the solvent gas generator 93 to produce a mixed gas. The mixed gas is sent to the chamber 82. Note that the same effect can be obtained even when the upstream and downstream relationships between the humidifier 91 and the solvent gas mixer 93 are reversed and the solvent gas mixer 93 is disposed upstream of the humidifier 91.

  Moreover, you may replace the 1st air blower 48 and the 1st controller 49 of FIG.5 and FIG.7 with the humidifier 91, the 3rd air blower 92, and the 5th controller 108 of FIG. Then, the second blower 54 and the second controller 55 in FIG. 5 may be replaced with the solvent gas generator 93, the fourth blower 94, and the sixth controller 110 shown in FIG.

[material]
A hydrophobic polymer is used as the polymer. An amphiphilic compound may be added to this hydrophobic polymer. Amphiphilic compounds have hydrophilicity and lipophilicity. Specifically, they are compounds having a hydrophilic group and a hydrophobic group. By using this, water droplets are more easily formed on the liquid surface of the polymer solution. .

  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%.

  The solvent used as the solvent for the polymer solution and the supplied solvent gas are not particularly limited as long as they dissolve the hydrophobic polymer. Examples include chloroform, dichloromethane, carbon tetrachloride, cyclohexane, methyl acetate and the like. Further, the solvent serving as the solvent of the polymer solution and the supplied solvent gas may be different compounds. Furthermore, the solvent used as the solvent of the polymer solution and the supplied solvent gas may be a mixture of two or more compounds or may have different compositions.

  By using two or more compounds different from each other as the solvent and appropriately changing the ratio, the growth rate of water droplets, the time required for growth, and the like can be controlled. As the solvent gas in this case, among the solvent components in the polymer solution, those that are most easily evaporated in the water droplet forming step may be used.

  The polymer solution is preferably prepared so that the hydrophobic polymer is 0.02 parts by weight or more and 20 parts by weight or less with respect to 100 parts by weight of the organic solvent. And it is preferable to adjust the easiness of flow of the solution, that is, the fluidity within this weight concentration range.

  For polymer solutions, the higher the viscosity is, the more difficult the water droplets generated by condensation move and the more difficult the polymer solution itself flows. The lower the viscosity, the water droplets are more likely to combine and coalesce and the pore size is uneven. And the casting solution itself tends to flow. Therefore, it is preferable that the viscosity is in the range of 0.1 mPa · s to 50 mPa · s, and the easiness of flow of the solution is adjusted in this range. By adjusting the ease of flow of the polymer solution, the thickness T, the pore diameter D, and the pore diameter difference can be adjusted.

Polymer solution 33 was prepared with the following formulation.
Polybutadiene 1 part by weight Dichloromethane 100 parts by weight Block copolymer of polyethylene glycol and polypropylene glycol
0.1 parts by weight

  After the polymer solution 33 was placed on the support 32, it was left to stand in a dry atmosphere until the polymer solution 33 spreads out. With the liquid film 31 thus formed placed on the support 32, the water droplet forming step 21, the solvent evaporation step 22, the water droplet evaporation step 23, and the solvent gas supply step 24 are performed using the porous film manufacturing apparatus 81. It carried out on condition of this.

  In the generation step 21 a of the water droplet formation step 21, the temperature of the water 96 in the water tank 97 was 25 ° C., and the dew point in the space on the water surface inside the water tank 97 was 20 ° C. Thereby, the temperature of the humidified air exiting from the water tank 97 was set to 25 ° C., and the dew point was set to 20 ° C. The supply time of the humidified air into the chamber 82 was 3 minutes.

  In the growth step 21 b of the water droplet formation step 21, the temperature of the water 96 was 25 ° C., and the dew point in the space on the water surface inside the water tank 97 was 17 ° C. As a result, the temperature of the humidified air coming out of the water tank 97 was 25 ° C., and the dew point was 17 ° C. The supply time of the humidified air into the chamber 82 was 10 minutes.

  In the arranging step 21c of the water droplet forming step 21, the temperature of the water 96 was 25 ° C., and the dew point in the space on the water surface inside the water tank 97 was 15 ° C. As a result, the temperature of the humidified air exiting from the water tank 97 was 25 ° C., and the dew point was 15 ° C. The supply time of the humidified air into the chamber 82 was 3 minutes.

  In addition, in the water droplet formation process 21 of the generation | occurrence | production process 21a-the arrangement | sequence process 21c, the liquid level temperature of the liquid film 31 was hold | maintained at 5 degreeC by the temperature adjustment part 61. FIG.

  In the solvent evaporation step 22, the temperature of the water 96 was 25 ° C., and the dew point in the space above the water surface inside the water tank 97 was 15 ° C. As a result, the temperature of the humidified air exiting from the water tank 97 was 25 ° C., and the dew point was 15 ° C. The supply time of the humidified air to the inside of the chamber 82 was set to 10 minutes, during which time the solvent was evaporated.

  In the water droplet evaporation step 23, the temperature of the water 96 was 25 ° C., and the dew point in the space above the water surface inside the water tank 97 was 15 ° C. As a result, the temperature of the humidified air exiting from the water tank 97 was 25 ° C., and the dew point was 15 ° C. The supply time of the humidified air to the inside of the chamber 82 was 3 minutes, during which water droplets and the remaining solvent were evaporated. In the water droplet evaporation step 23, the liquid surface temperature of the liquid film 31 was maintained at 10 ° C. by the temperature adjusting unit 61.

  The solvent gas supply step 24 was performed in all the steps of the water droplet formation step 21, that is, the generation step 21a to the arrangement step 21c. Solvent 74 is dichloromethane. The temperature of the solvent 74 in the liquid tank 102 was 15 ° C. The temperature of the solvent gas exiting from the liquid tank 102 was 25 ° C. The supply time of the humidified air to the inside of the chamber 82 was 3 minutes, during which water droplets and the remaining solvent were evaporated.

About the obtained porous film 10, it evaluated about the hole diameter D1 and the uniformity including the arrangement | sequence of the hole 11. FIG. For uniformity, the pore diameter D1 of the porous film 10 was measured to calculate the pore diameter variation coefficient X, and this calculated value was evaluated in accordance with the following criteria. The hole diameter variation coefficient X is determined by {(standard deviation of hole diameter) / (average value of hole diameter)} × 100.
◎: When the pore diameter variation coefficient X is 5% or less ○: When the pore diameter variation coefficient X is greater than 5% and 10% or less ×: When the pore diameter variation coefficient X is greater than 10%

Based on the hole diameter D1 and uniformity, comprehensive evaluation was performed according to the following criteria. Each evaluation result is shown in Table 1.
A: The hole diameter D1 is 20 μm or more, and the uniformity is ◎
B: The hole diameter D1 is 10 μm or more and less than 20 μm, and the uniformity is good.
C: The hole diameter D1 is 10 μm or more and less than 20 μm, and the uniformity is ×
D: The hole diameter D1 is less than 10 μm, and the uniformity is ×

  The solvent gas supply step 24 was performed only in the generation step 21a and the growth step 21b in the water droplet formation step 21, and not in the arrangement step 21c. Other conditions are the same as those in the first embodiment. Then, the obtained porous film 10 was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

  The solvent gas supply step 24 was performed only in the growth step 21b and the arrangement step 21c in the water droplet formation step 21, and not in the generation step 21a. Other conditions are the same as those in the first embodiment. Then, the obtained porous film 10 was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

  The solvent gas supply step 24 was performed only in the generation step 21a in the water droplet formation step 21, and was not performed in the growth step 21b and the arrangement step 21c. Other conditions are the same as those in the first embodiment. Then, the obtained porous film 10 was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

  The solvent gas supply step 24 was performed only in the growth step 21b in the water droplet formation step 21, and was not performed in the generation step 21a and the arrangement step 21c. Other conditions are the same as those in the first embodiment. Then, the obtained porous film 10 was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

  The solvent gas supply process 24 was performed only in the arrangement process 21c in the water droplet formation process 21, and was not performed in the generation process 21a and the growth process 21b. Other conditions are the same as those in the first embodiment. Then, the obtained porous film 10 was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

  The solvent gas supply step 24 was performed in all the steps of the water droplet formation step 21, that is, the generation step 21a to the arrangement step 21c. The conditions are the same as in Example 1 except that the supply time of the humidified air to the inside of the chamber 82 in the growth step 21b is 7 minutes. Then, the obtained porous film 10 was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

[Comparative Example 1]
The solvent gas supply step 24 was not performed. Other conditions are the same as those in the first embodiment. Then, the obtained porous film 10 was evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1.

  The porous films 10 obtained in Examples 1 to 3 and 5 to 7 each have a pore diameter of 10 μm or more, which is larger than the conventional porous film, and is excellent in uniformity as the porous film 10. In Example 4, although the portion where the uniformity was inferior to that of Examples 1 and 3 was slightly observed, the hole 11 having a hole diameter of 10 μm or more could be formed. For example, the porous film 10 of Example 7 shown in FIG. 9 has larger pores than the film of Comparative Example 1 shown in FIG. 10, and the uniformity as a film is very excellent. Thus, it can be seen from the examples and comparative examples that according to the present invention, a porous film having a honeycomb structure in which a plurality of holes having a diameter of 10 μm to several tens of μm are formed can be obtained.

DESCRIPTION OF SYMBOLS 10 Porous film 11 Hole 31 Liquid film 33 Polymer solution 41,71,81 Porous film manufacturing apparatus 43 Air supply part 44 Solvent gas supply part 74 Solvent 76 Temperature adjustment part 83 Mixed gas supply part 91 Humidifier 93 Solvent gas generator 95 Mixing Machine D1 Hole diameter D2 Opening diameter

Claims (4)

In the method for producing a porous film in which a plurality of holes are formed on the film surface,
A water droplet forming step in which water in the atmosphere is condensed in a solution in which the polymer is dissolved in a solvent to form water droplets;
A solvent evaporation step of evaporating the solvent from the solution so that the water droplets do not evaporate;
A water droplet evaporation step for evaporating the water droplets;
And a solvent gas supply step of supplying a solvent gas onto the solution so as not to evaporate the solvent from the solution before the solvent evaporation step. Method.   2. The solvent gas supply step according to claim 1, wherein the solvent gas is supplied onto the solution by disposing the solution in a chamber and feeding the solvent gas into the chamber. A method for producing a porous film.   In the solvent gas supply step, the solvent and the liquid that becomes the solvent gas are arranged in a chamber, and the liquid is evaporated in the chamber, whereby the solvent gas is supplied onto the solution. The method for producing a porous film according to claim 1. The method for producing a porous film according to any one of claims 1 to 3 , wherein in the water droplet forming step, humidified air is supplied onto the solution.

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