CN107632335B

CN107632335B - Method and system for manufacturing polarizing film

Info

Publication number: CN107632335B
Application number: CN201711064810.3A
Authority: CN
Inventors: 林鸿棋; 郭建生; 徐维廷
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2017-09-13
Filing date: 2017-11-02
Publication date: 2020-06-16
Anticipated expiration: 2037-11-02
Also published as: JP7199882B2; CN107632335A; KR102536035B1; KR20200068012A; TWI640556B; JP2019053294A; TW201915058A

Abstract

A method and system for manufacturing a polarizing film. The method comprises the following steps. A polarizing film precursor is passed through a first solution. An electrode group in contact with the first solution is used for carrying out precipitation treatment on the first solution to form a second solution. And carrying out filtration treatment on the second solution to form a third solution.

Description

Method and system for manufacturing polarizing film

Technical Field

The present invention relates to a method and system for manufacturing a polarizing film, and more particularly, to a method and system for manufacturing a polarizing film by electrocoagulation using an electrode set.

Background

A polarizing film is an optical element widely used in liquid crystal displays. Nowadays, liquid crystal displays are increasingly used, for example, mobile phones, wearable devices, etc., and the requirements for the quality of the polarizing film are also increasing.

The polarizing film comprises a polarizing film, which is generally formed by adsorbing aligned dichroic pigments on a polyvinyl alcohol film. The formation of the polarizing film generally has the following steps: swelling treatment, dyeing treatment, stretching treatment, crosslinking treatment, washing treatment and drying treatment. Wherein the stretching treatment imparts a polarizing effect to the polyvinyl alcohol.

Disclosure of Invention

The invention aims to provide a method and a system for manufacturing a polarizing film.

According to an aspect of the present invention, there is provided a method for manufacturing a polarizing film, including the following steps. A polarizing film precursor is passed through a first solution. An electrode group in contact with the first solution is used for carrying out precipitation treatment on the first solution to form a second solution. And carrying out filtration treatment on the second solution to form a third solution.

According to another aspect of the present invention, a system for manufacturing a polarizing film includes a processing bath, a guide roller, an electrode group, and a filtering device. The treatment tank includes a solution. The guide roller is used for conveying a polarizing film precursor through the solution. The electrode group contacts the solution after the polarizing film precursor passes through. The filtering device is used for filtering the solution after the electrode is connected.

The invention is described in detail below with reference to the drawings and specific examples, but the invention is not limited thereto.

Drawings

FIG. 1 shows a system for making a polarized film;

fig. 2 shows a system for manufacturing a polarizing film according to an embodiment concept;

fig. 3 shows a system for manufacturing a polarizing film according to an embodiment concept;

fig. 4 depicts a system for manufacturing a polarized film according to an embodiment concept.

Wherein the reference numerals

3: overflow device

31: drainage plate

32: box body part

37. 137: circulation system

101: treatment tank

102: unwinding roller

103: first channel

104: bentonite tank

105: precipitation tank

106: dyeing tank

107: the second channel

108: cross-linking groove

109: filter device

110: cleaning tank

111: third channel

112: drying furnace

114: winding roller

116A: first slot part

116B: second slot part

118: filter membrane

120: guide roller

130: first channel

133: the second channel

200: polarizing film precursor

200': polarizing film

318: filter element

E: electrode group

E1: first electrode element

E2: second electrode element

L1: first solution

L2: second solution

L3: the third solution

P1: first chip body

P2: second chip

Detailed Description

The invention will be described in detail with reference to the following drawings, which are provided for illustration purposes and the like:

in the polarizing film process, a polarizing film precursor is easy to crack after being stretched, and when the polarizing film precursor passes through a liquid medicine tank, scraps can be separated and distributed in liquid medicine and accumulated to a certain degree, the film surface of the polarizing film can be defective.

Embodiments of the present disclosure provide a method and system for manufacturing a polarizing film. The method can effectively reduce the possibility that scraps in the solution are attached to the precursor of the polarizing film to influence the product property.

It should be noted that the present invention is not intended to show all possible embodiments, and other embodiments not suggested by the present invention may also be applicable. Moreover, the dimensional ratios in the drawings are not drawn to scale according to actual products. Accordingly, the description and drawings are only for the purpose of illustrating embodiments and are not to be construed as limiting the scope of the invention. Moreover, the descriptions of embodiments, such as specific structures, process steps, and material applications, are provided for illustrative purposes only and are not intended to limit the scope of the present disclosure. The details of the steps and structures of the embodiments may be varied and modified as required by the actual implementation without departing from the spirit and scope of the invention. The following description will be given with the same/similar reference numerals as used for the same/similar elements.

Fig. 1 shows a system for manufacturing a polarizing film. The system shown in FIG. 1 includes an unwinding roll 102, a swelling tank 104, a dyeing tank 106, a crosslinking tank 108, a washing tank 110, a drying oven 112, and a winding roll 114. The processing tanks and processing equipment may be selectively increased, decreased, reconfigured, or otherwise adjusted. After a polarizing film precursor 200 is unwound from the unwinding roll 102, it is guided and conveyed by the guide roll 120, sequentially passing through the respective processing tanks and processing equipment as indicated by arrows. The formed polarizing film 200' is rewound on the winding roller 114 for transportation.

The material of the polarizing film precursor 200 includes Polyvinyl alcohol (PVA) or other suitable material. For example, the polarizing film precursor 200 may be a film of polyvinyl alcohol. Polyvinyl alcohol can be formed by saponifying polyvinyl acetate. According to some embodiments, the polyvinyl acetate may be a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and other monomers, which may be unsaturated carboxylic acids, olefins, unsaturated sulfonic acids, or vinyl ethers, among others. In some embodiments, the polyvinyl alcohol is modified, such as polyvinyl formal (pvformal), polyvinyl acetate, or polyvinyl butyral (pvybutyral) that are aldehyde modified, among others. In some embodiments, the polarizing film precursor 200 has a thickness of about 20 μm to about 100 μm.

The polarizing film precursor 200 may be guided to the swelling tank 104 by the guiding roller 120 to perform a swelling process on the polarizing film precursor 200. The swelling treatment can remove foreign materials on the surface of the polarizing film precursor 200 and plasticizer in the polarizing film precursor 200, and facilitate the subsequent dyeing treatment and crosslinking treatment.

According to some embodiments, an extension process may be performed on the polarized film precursor 200 in the system for manufacturing a polarized film. The extension treatment may be performed while passing through the swelling tank 104, and/or the subsequent dyeing tank 106, and the crosslinking tank 108. For example, the uniaxial stretching treatment can be performed by making the difference in the circumferential velocity between the guide roller 120 provided at the inlet of the swelling tank 104 and the guide roller 120 provided at the outlet of the swelling tank 104. According to some embodiments, the cumulative draw ratio of the polarizing film precursor 200 is about 4.5 times to 8 times from the swelling treatment to the crosslinking treatment.

The polarizing film precursor 200 is then guided to the dyeing tank 106 by the guide roller 120 to perform a dyeing process on the polarizing film precursor 200. The bath solution in the staining bath 106 contains a staining agent. The coloring agent may use a dichroic pigment, or other suitable water-soluble dichromatic dye. In some embodiments, the stain comprises iodine and potassium iodide. For example, the coloring agent may be an aqueous solution including 0.003 to 0.2 parts by weight of iodine and 3 to 30 parts by weight of potassium iodide. In some embodiments, the temperature of the dyeing process is 10 ℃ to 50 ℃ and the time of the dyeing process is 10 seconds to 600 seconds. Other additives, such as boric acid, may be included in the bath solution to enhance the dyeing process.

The polarizing film precursor 200 is then guided to the cross-linking tank 108 by the guiding roller 120 to perform a cross-linking process on the polarizing film precursor 200. The bath solution in the crosslinking bath 108 contains a crosslinking agent. Boric acid may be used as the crosslinking agent. The bath solution in the crosslinking bath 108 may further contain an optical modifier. The color of the polarizing film can be adjusted by changing the concentration of the optical adjusting agent. The optical modifier may use potassium iodide, zinc iodide, or a combination thereof. In some embodiments, the temperature of the cross-linking treatment may be 10 ℃ to 70 ℃ and the time of the cross-linking treatment may be 1 second to 600 seconds. In some embodiments, the bath solution of the crosslinking bath 108 may contain a precipitate of the polarizing film precursor 200, such as a polyvinyl alcohol-based precipitate. The precipitate is insoluble debris produced by the action of the dissolved polyvinyl alcohol and boric acid.

Fig. 2 shows a system for manufacturing a polarizing film according to an embodiment concept. The bath solution in the treatment bath 101 was the first solution L1. The guide roller 120 conveys the polarizing film precursor 200 through the first solution L1 in the processing tank 101.

In one embodiment, the processing tank 101 is a dyeing tank 106 as shown in fig. 1, and the first solution L1 disposed therein is a chemical solution for dyeing the polarizing film precursor 200, such as an aqueous solution containing dissociated iodide ions. In another embodiment, the processing bath 101 is a crosslinking bath 108 as shown in fig. 1, and the first solution L1 disposed therein is boric acid, potassium iodide, zinc iodide, or a combination thereof.

In an embodiment, the first solution L1 may contain first chips P1. For example, the first chip P1 may include undesired chips caused by the polarizing film precursor 200 passing through the first solution L1, such as chips that are dropped, dissolved or precipitated from the polarizing film precursor 200, or other organic foreign substances in the processing bath 101. In the examples, the first flakes P1 distributed in the first solution L1 had a particle size ranging from 10nm to 1000 nm.

In one embodiment, the processing tank 101 may be in communication with the circulation system 37. The circulation system 37 may include a first channel 103, an extraction tank 105, a second channel 107, a filtration device 109, and a third channel 111.

In one embodiment, the first chips P1 can be processed by the separating tank 105 of the recycling system 37 to become larger in size to form second chips P2, and then filtered by the filtering device 109.

The first channel 103 communicates between the processing bath 101 and the precipitation bath 105, and provides a path for the first solution L1 in the processing bath 101 to flow into the precipitation bath 105 and enter the precipitation bath 105. The first solution L1 may be driven using a pump (not shown).

The electrode group E is provided in the precipitation tank 105. The electrode group E includes a first electrode element E1 and a second electrode element E2 with opposite polarities, for example, a positive electrode and a negative electrode. The material of the first electrode element E1 and the second electrode element E2 includes, but is not limited to, metal, such as iron, aluminum, nickel, copper, and other suitable conductive materials. The first electrode element E1 and the second electrode element E2 may be immersed in the solution and brought into contact with the solution, and the solution is precipitated by applying a voltage or a current, thereby forming a second solution L2 containing the precipitated second debris P2. In one embodiment, second chips P2 are first chips P1 in the first solution L1, and are processed to form second chips P2 with increased sizes, such as particle sizes. In other words, the size of the second chip bodies P2 in the second solution L2 is larger than the size of the first chip bodies P1 in the first solution L.

In the examples, the above treatment was carried out by Electrocoagulation (Electrocoagulation). That is, the first chips P1 in the first solution L1 were charged with electric current, and the charge distribution on the surface of the first chips P1 was changed, and the first chips P1 were aggregated to form the second chips P2.

In one embodiment, the current value of the electrode set E is, for example, between 0.2 and 5.0 amperes, preferably between 0.2 and 1 ampere. In the examples, the particle size of the second chips P2 ranged from 2 μm to 10 μm.

The second passage 107 communicates between the precipitation tank 105 and the filtration device 109, and provides a path for the second solution L2 in the precipitation tank 105 to flow to the filtration device 109, and then enters the filtration device 109 for filtration. A pump (not shown) may be used to drive the second solution L2.

For example, the filter assembly 109 may include a first trough portion 116A, a second trough portion 116B, and a filter membrane 118. The second passage 107 communicates between the precipitation tank 105 and the first tank section 116A of the filtration apparatus 109, and can provide a path for the second solution L2 in the precipitation tank 105 to flow to the first tank section 116A to enter the first tank section 116A. Filter membrane 118 is disposed between first trough section 116A and second trough section 116B and is adapted to filter second solution L2 from first trough section 116A into third solution L3 which enters second trough section 116B.

In the embodiment, the filtration membrane 118 has filtration pores with a pore size selected to block the second chip bodies P2 in the second solution L2, which have a larger pore size than the filtration pores, so that the third solution L3 flowing out through the filtration membrane 118 does not contain the second chip bodies P2 formed of the first chip bodies P1. Alternatively, the second scraps P2 are filtered by the filtering device 109. In the embodiment, for example, the pore size of the filtration pores of the filtration membrane 118 is 1 μm to 10 μm, or 2 μm to 10 μm, or 1 μm to 2 μm, which is much larger than the pore size of the filtration pores used in the general ultrafiltration technology, from 2nm to 100 nm.

In another embodiment, because the second chip P2 is larger in size than the first chip P1, the filter membrane 118 may be selected to have smaller pores than the second chip P2 but larger pores than the first chip P1, wherein the larger pore size filter membrane 118 is less costly and has a longer useful operating life and may be periodically serviced after a longer period of operation. However, the invention is not limited thereto, and in other embodiments, for example, the filter membrane 118 may be selected to have a smaller size than the first chip P1, and both the first chip P1 and the second chip P2 may be removed.

The third channel 111 communicates between the filtering device 109 and the treating tank 101 and may provide a path for the third solution L3 formed by filtering in the filtering device 109 to flow toward the treating tank 101 to enter the treating tank 101. Specifically, the third passage 111 communicates between the second tank section 116B of the filter unit 109 and the processing tank 101. A pump (not shown) may be used to drive the third solution L3. Since the third solution L3 does not contain the second chips P2, the content ratio of the first chips P1 can be reduced after the first solution L1 in the treatment tank 101 is mixed and diluted with the third solution L3, so that the effect of cleaning the first solution L1 is achieved.

The system of an embodiment may be a continuous process system. That is, while the processing bath 101, the deposition bath 105, and the filtering device 109 are in communication to continuously clean the solution, the polarizing film precursor 200 is maintained to be transferred through the processing bath 101 by the guide roller 120 for the processing process, and the processing process of the polarizing film precursor 200 does not need to be stopped intentionally, thereby not affecting productivity. Furthermore, through the treatment of the precipitation tank 105 and the filtering device 109, the content ratio of the first chips P1 in the first solution L1 can be controlled within the acceptable lower limit specification of the process control, and the problem of structural defects caused by the adhesion of the first chips P1 to the treatment tank 101 is avoided, thereby improving the product yield. Specifically, in the case where the polarizing film precursor 200 is continuously passed through the first solution L1 and the first chip P1 may be continuously generated, using the system for continuously removing the first chip P1 according to the concept of the present invention, the first chip P1 can be prevented from being continuously accumulated in the first solution L1, and thus the first chip P1 in the first solution L1 can be controlled within the acceptable specification in the process control. In addition, the first solution L1 can be filtered and continuously recycled without stopping the processing tank 101 to replace extra clean solution, thereby reducing the cost and improving the productivity.

In other embodiments, a control valve (not shown) may be disposed in the first channel 103, the second channel 107 and/or the third channel 111 to control the flow of the first channel 103, the second channel 107 and/or the third channel 111, thereby improving the operation flexibility of the system. For example, when the precipitation tank 105 and/or the filtering device 109 needs to be shut down for inspection or periodic maintenance, the control valves (not shown) of the first channel 103, the second channel 107 and/or the third channel 111 can be closed to prevent the first solution L1 from flowing out of the processing tank 101, so that even if the precipitation tank 105 and/or the filtering device 109 is not used, the polarized film precursor 200 can be continuously processed through the processing tank 101 without being affected by the precipitation tank 105 and/or the filtering device 109.

By the continuous circulating system, the content of the first chip P1 in the first solution L1 can be controlled within the acceptable lower limit specification in the process control, the first solution L1 is kept at the expected cleanliness, the quality problem of structural defects caused by the fact that the excessive first chip P1 is attached to the surface of the polarizing film precursor 200 due to the fact that the undesirable PVA chip is attached to the surface of the polarizing film precursor is avoided, and the product yield is improved.

In one embodiment, even though the first solution L1 does not contain boric acid, the precipitation tank 105 can still perform precipitation reaction on the first solution L1, and the electrocoagulation gel forms the second filings P2 on the first filings P1, so that the system and method of the present invention can be applied to a wide variety of solutions. In one embodiment, for example, the first solution L1 uses a dyeing solution, such as an aqueous solution containing dissociated iodide ions, which does not contain boric acid.

The method for detecting the content of PVA in the solution includes the calculation of the total organic carbon content (TOC).

The mechanism of the precipitation tank for aggregating the first chip bodies P1 into the second chip bodies P2 is presumed in the examples to be that, during the period of applying current to the electrode group E for precipitation treatment, water molecules in the first solution L1 chemically react with the electrode group E to form a metal hydroxide as an aggregate on the surfaces of the first electrode element E1 and the second electrode element E2 (including a metal material), and the first chip bodies P1 are adsorbed on the metal hydroxide to form a gel, so that the volume thereof increases and becomes the second chip bodies P2.

Fig. 3 shows a system for manufacturing a polarizing film according to another embodiment concept. The processing tank 101 stores a first solution L1, and may include an electrode set E and at least one overflow device 3. The electrode group E may be immersed in the solution and contacted with the solution, and the solution may be precipitated by applying a voltage or a current, so as to form a second solution L2 containing precipitated second filings P2 (not shown in fig. 3). The overflow device 3 may comprise a flow-guiding plate 31 and a first channel 130 (e.g. a drain). The position of the drainage plate 31 of the overflow device 3 can be adjusted below the liquid level of the solution to guide the solution into and discharge the solution to the circulation system 137 outside the treatment tank 101 through the first passage 130. Herein, the circulating system 137 may be provided with a filtering device 109 for filtering out the second scraps P2 in the second solution L2. The filtered and purified third solution L3 can then be recycled back to the treatment tank 101 for use via the second channel 133.

Fig. 4 depicts a schematic diagram of a processing tank 101 according to one embodiment concept. The overflow device 3 may comprise a box portion 32. The drainage plate 31 is movably disposed on at least one side of the case portion 32 such that the position of the drainage plate 31 can be adjusted according to the level of the solution. In another embodiment, the overflow device 3 may further include a filter member 318. The filter member 318 is detachably disposed in the case portion 32. The filter 318 may be, for example, a filter screen and/or a filter membrane. The filter element 318 may initially filter debris to further increase the effectiveness of filtering debris. The aperture of the filtration pore of the filtration membrane is 1 μm to 10 μm, or 2 μm to 10 μm, or 1 μm to 2 μm, which is much larger than the aperture size of the filtration pore used by the general ultrafiltration technology, 2nm to 100 nm.

In order to make the above-mentioned aspects of the present invention more comprehensible, the following specific examples are described in detail:

2L of pure water, 40 g of potassium iodide, 5 g of iodine and 0.5 g of PVA solid (with the particle size of 0.1-0.5 mm) are uniformly mixed and stirred until no precipitate is formed, thus obtaining a first solution.

Examples 1 to 4 at room temperature, 80ml/min was set by a peristaltic pump, the first solution was introduced into a precipitation tank, and after electrocoagulation was performed by adjusting different current values to an electrode group (the portion of the first electrode element and the second electrode element immersed in the solution had a size of 2 cm in width and 6 cm in height) to form a second solution, the second solution was filtered to obtain a third solution. Wherein the filtration uses a filtration membrane having a filtration pore size of 1 μm to 2 μm (micrometer).

It can be seen from examples 1-4 that the applied current boost facilitates the removal of more PVA solids, resulting in a better reduction in the PVA solids content. With example 3 having the highest benefit. In example 4, although the current is further increased, the extent of decrease in the PVA solid content is not as great as in example 3, and it is presumed that the saturation of the ions dissociated in the second solution in the precipitation step is limited, and an excessively high current value does not further increase the concentration of the dissociated ions in the saturated second solution, and an excessively high current value causes consumption of extra energy, which increases unnecessary manufacturing costs, and is not economical. Table 1 shows the current values of the electrode groups in the deposition steps of examples 1 to 4, the total organic carbon contents before and after the solution treatment (the total organic carbon content before the treatment is the total organic carbon content C1 of the first solution, and the total organic carbon content after the treatment is the total organic carbon content C2 of the third solution), and the PVA solid removal rates calculated from the difference between the total organic carbon contents before and after (i.e., (C1-C2)/C1). The total organic carbon content was measured using a total organic carbon content (TOC) analyzer.

Comparative example 1 the first solution was filtered through a filter membrane using an ultrafiltration method with a peristaltic pump setting of 80 ml/min. Although having a high removal rate, the ultrafiltration method requires the use of a filtration membrane having a very small filtration size (pore size of 2nm to 100nm), which is expensive, and which is quickly clogged with debris and is not efficiently filtered, has a short effective working life, and requires high frequency replacement, thus being economically inefficient. The total organic carbon content before and after the treatment of the solution in comparative example 1 shown in Table 1 (the total organic carbon content before the treatment was C1 which was the total organic carbon content of the first solution, and the total organic carbon content after the treatment was C1 ') and the PVA solid removal rate calculated from the difference between the total organic carbon content before and after the treatment (i.e., (C1-C1')/C1).

Comparative example 2 the first solution was filtered using a low temperature filtration method. Wherein the first solution is firstly cooled to a low temperature (5 ℃) lower than the room temperature, and then the peristaltic pump is used for setting 80ml/min to push the first solution to pass through a filter membrane with the filter pore size of 1-2 mu m for filtering in a low-temperature environment. The total organic carbon content before and after the treatment of the solution in comparative example 1 shown in Table 1 (the total organic carbon content before the treatment was C1 which was the total organic carbon content of the first solution, and the total organic carbon content after the treatment was C1 ') and the PVA solid removal rate calculated from the difference between the total organic carbon content before and after the treatment (i.e., (C1-C1')/C1). The removal rate of the PVA solid in comparative example 2 is far lower than that in examples 1 to 3 and comparative example 1, and it is presumed that the PVA solid in the first solution cannot be removed from the first solution by the filtration membrane having a large filtration pore size because the first solution does not contain a boric acid component which can achieve the accumulation effect at a low temperature.

TABLE 1

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it should be understood that various changes and modifications can be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A method for manufacturing a polarizing film, characterized by comprising:

passing a polarizing film precursor through a first solution;

carrying out precipitation treatment on the first solution by utilizing an electrode group contacted with the first solution to form a second solution; and

and filtering the second solution to form a third solution.

2. The method for manufacturing a polarizing film according to claim 1, further comprising:

and enabling the polarizing film precursor to pass through the first solution mixed with the third solution or pass through the second solution mixed with the third solution.

3. The method for producing a polarizing film according to claim 1, wherein the first solution includes a first chip body, and the second solution includes a second chip body which is increased in size by a deposition treatment from the first chip body.

4. The method according to claim 3, wherein the first scrap comprises scraps produced when the polarizing film precursor passes through, the second solution comprises a second scrap which becomes larger in size from the first scrap through a precipitation treatment, and the filtration treatment comprises using a filtration device having filtration holes larger in size than the first scrap.

5. The method for manufacturing a polarizing film according to claim 4, wherein the particle diameter of the first chips is in a range of 10nm to 1000 nm; the particle size range of the second scraps is 2-10 mu m; and the pore diameter of the filter pores is 1 to 10 μm.

6. The method for manufacturing a polarizing film according to claim 1, wherein the first solution is a polarizing film dyeing solution containing iodide ions, or the first solution is boric acid, potassium iodide, zinc iodide, or a combination thereof.

7. A process for producing a polarized film according to claim 1 wherein the current value of the set of electrodes is between 0.2 and 5.0 amperes or the set of electrodes is used to perform an electrocoagulation process.

8. A system for manufacturing a polarizing film, comprising:

a treatment tank comprising a solution;

a guide roller for transmitting a polarizing film precursor through the solution;

an electrode group contacting the solution after the polarizing film precursor passes through; and

a filtering device for filtering the solution after the electrode is connected.

9. The system of claim 8, further comprising a recycling system disposed outside and in communication with the processing tank, wherein the recycling system comprises the electrode assembly and the filtering device.

10. The system for manufacturing a polarized film according to claim 8, wherein the electrode group is disposed in the processing bath.

11. The system of claim 8, wherein the electrode set is used to perform an electrocoagulation of the solution after the polarizer precursor passes through, or the current value of the electrode set is between 0.2 amperes and 5.0 amperes.

12. The system of claim 8, wherein the filtering device is an overflow device, and the overflow device further comprises a filter and a drainage plate.

13. The system according to claim 12, wherein the filter comprises a filter net and/or a filter membrane, and the aperture of the filter hole of the filter membrane is 1 μm to 10 μm.