JPH1024224A - Laminated porous film and its utilization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the service life of a filter by laminating a porous film showing a specific value of the bubble point due to isopropanol and porosity on the primary side of a porous film showing a specific value of bubble point due to isopropanol. SOLUTION: The porous film suitably used as the filter to remove foreign matters such as particulates in water, a liquid chemical or a solvent used in a cleaning line for liquid crystal and semiconductor fields is formed by laminating the porous film B having 0.4-1.0kg/cm<2> bubble point due to isopropanol and 60% porosity on the primary side of the porous film A having >=1.5kg/cm<2> bubble point due to isopropanol. And at this time, the laminated porous film is set to satisfy the relation of (C)/(A)<=1/2 when the average reduction speed of flow rate of the laminated porous film at the time of solvent filtration is expressed by (C) and the average reduction speed of flow rate of the porous film A is expressed by (A) and is formed to have >=85% stop-off ratio at the time of permeating a polystyrene latex having 0.15μm diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention provides a laminated porous membrane having excellent filtration characteristics and permeation performance and less clogging. Further, the porous membrane of the present invention can easily control the permeability and the pore size, and provides a porous membrane suitable for a filtration membrane, a battery separator, various packaging materials requiring a gas permeability, a medical material, a clothing material and the like. Can be. In particular, the present invention provides a porous film suitable for a method for producing a photoresist.

[0002]

2. Description of the Related Art Porous membranes are used in various industrial fields such as filtration membranes, battery separators, packaging, medical and clothing materials. In particular, in the liquid crystal and semiconductor fields, various types of porous membranes are used as filters for removing foreign substances such as fine particles in water, chemicals, and solvents used in cleaning lines. In particular, with the improvement in the degree of integration of semiconductors, these filters
The required performance is increasing year by year.

For example, a photoresist which is indispensable for forming a fine pattern of an LSI has a minimum pattern in the megabit era.
With the sub-micron size, 1/5 to 1 /
Even fine particles having a diameter of 10 are to be removed, and a filter is required to have high rejection. On the other hand, in order to efficiently purify a resist having a high viscosity, a higher processing capacity is required for a filter. Thus high rejection,
The conflicting performance of high throughput is also required at the same time. As a method for producing such a high-performance porous membrane, for example, a method described in JP-A-3-80923 is exemplified. In the same issue, the water permeation speed is 3000L
/ Hr · m ² · atm or more, and a polyethylene porous membrane having a rejection of 0.091 μm polystyrene latex of 95% or more is disclosed. Japanese Patent Application Laid-Open No. 5-307263 discloses that such a filtration membrane having a high blocking performance is used for producing a resist composition.

[0004]

However, a porous membrane having high blocking properties and high permeability has a short blocking time due to foreign matters due to its high blocking properties and high transmission speed, and maintains high permeability performance. This requires frequent replacement of the filter, which is costly. In order to solve such a problem, conventionally, at a site where a filter is used, in order to prevent the filter from being clogged, a plurality of filters having different pore sizes are combined and the solvent is filtered in the order of the pore size to sequentially remove large foreign substances. Was removed to prevent clogging of the final filter. However, these have probably been performed empirically and have not been based on quantitative data.

Further, increasing the number of filters in order to prevent clogging increases the length of the piping and increases the contamination of the system, thereby increasing the cost of cleaning the system. In particular, in recent years when the pore diameter of the final filter is reduced to 0.1 μm to 0.05 μm, prevention of contamination and more efficient cleaning of the system are required more than before. The present invention solves such problems and provides a porous membrane having a long service life in addition to high blocking properties and high permeability.

[0006]

Means for Solving the Problems The inventors of the present invention have made intensive studies in view of the above problems, and as a result, have formed a porous membrane having a bubble point of 0.4 to 1 kg / cm ² by isopropanol as a conventional filter. It has been found that by laminating the filter on the primary side of the porous film, the life of the filter can be significantly improved.

That is, the gist of the present invention is that the bubble point of isopropanol is 0.4 to 1.0 kg on the primary side of the porous membrane A having a bubble point of 1.5 kg / cm ² or more. / Cm ² and a porosity of at least 60%.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, when a porous membrane B is laminated on the primary side of a porous membrane A, the bubble point value of the porous membrane B due to isopropanol is 0.4 to 1 kg / cm ² . As a result, the inventors have found that the decrease in the filtration flow rate of the solvent is greatly reduced. According to the present invention, it is possible to suppress a decrease in the flow velocity of the filter to 以下 or less as compared with a case where the filter is not used.

Further, since the use of a plurality of filters is not required, the contamination from the piping as described above can be minimized. In addition, since the life of the filter is extended, the number of filters used can be reduced and the cost merit can be increased. In addition, since the number of filters discarded after use can be reduced, an advantage in environmental protection can be obtained.
Further, the cost merit due to the reduction of the filter installation space can be enjoyed.

In the laminated porous membrane of the present invention, the bubble point of isopropanol is 0.4 to 1.0 kg on the primary side of the porous membrane A having a bubble point of 1.5 kg / cm ² or more by isopropanol. / cm first ² a is and porosity has a structure obtained by laminating a porous membrane B is at least 60%, will be described porous membrane B of the present invention.

As a resin constituting the porous membrane B of the present invention, polyolefins having a molecular weight of tens of thousands to several millions, fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride, polyamides and the like can be used.
Among them, polyolefins having a viscosity-average molecular weight of 400,000 or more are preferable from the viewpoints of chemical resistance, low elution property and the like, more preferably polyolefins having a viscosity-average molecular weight of 1,000,000 or more, and particularly preferably polyethylene having a viscosity-average molecular weight of 1,000,000 or more. In addition, depending on the solvent to be filtered, the problem of adsorption of the contained composition may occur. In such a case, the resin constituting the porous membrane B can be appropriately selected.
It is not necessary to be limited to the single material mentioned above, and it is also possible to use a mixture of two or more polymers.

When the above resin is formed into a film, it is necessary to add a plasticizer to improve the moldability. The plasticizer is appropriately selected depending on the polymer. For example, in the case of polyolefin, paraffin wax, caprylic alcohol, lauryl alcohol, palmityl alcohol,
Aliphatic compounds such as higher aliphatic alcohols such as stearyl alcohol are used.

The mixing ratio of the polymer and the plasticizer is as follows.
The appropriate amount of the plasticizer is from 99 to 70 parts by weight to the amount of from 30 to 30 parts by weight. When the proportion of the polymer is 1 part by weight or less, the obtained film cannot have practical mechanical strength, and when it is 30 parts by weight or more, the amount of pores formed by extracting the plasticizer is small, and the present invention is aimed at. Such effects cannot be obtained. When the resin is polyolefin, the mixing ratio of the polymer and the plasticizer is polymer 1
The plasticizer is preferably 99 to 70 parts by weight to 30 to 30 parts by weight. More preferably, 5 to 20 parts by weight of the polymer is 95 to 80 parts by weight of the plasticizer, and particularly preferably, 10 to 20 parts by weight of the polymer is 90 to 80 parts by weight of the plasticizer.

As a method for forming the resin into a film, a known technique of batch or continuous is used. For example, a single-screw or twin-screw extruder equipped with a T die or an annular die at the tip is used. For the removal of the plasticizer, depending on the type of plasticizer, heptane, hexane, toluene, xylene, chloroform, methanol, ethanol, propanol, aliphatic such as alicyclic or aromatic hydrocarbons or halides thereof, Alternatively, a lower alcohol or the like is used. Almost all of the plasticizer is extracted, and the remaining amount of the plasticizer in the film is extracted to 1% or less, preferably to 0.1% or less.

In the present invention, stretching is performed after removing the plasticizer as necessary. Uniaxial or biaxial stretching is performed. As a stretching method, a roll stretching machine, a tenter stretching machine, or the like is used. The bubble point of the obtained porous membrane B by isopropanol is 0.4 to 1.0 kg / c.
m ² , preferably 0.5 to 0.8 kg / cm ² .
If it is less than 0.4 kg / cm ² , foreign matter or the like causing clogging will pass through the porous membrane B and cause clogging in the porous membrane A. If it exceeds 1.0 kg / cm ² , the expected effect cannot be obtained because the porous membrane B is clogged. The porosity of the porous membrane B is at least 60%, preferably at least 75%. If the porosity is less than 60%, the porous film B becomes a resistance, and the water permeability of the laminated film is remarkably reduced. As the thickness of the porous membrane B,
5 μm to 100 μm is preferred.

The porous membrane A must have a bubble point of 1.5 kg / cm ² or more due to isopropanol, preferably a polystyrene latex having a diameter of 0.15 μm having a rejection of 85% or more, particularly preferably a rejection of 85% or more. Rate 9
5% or more. If the bubble point or latex rejection is less than this value, it is not suitable for use in a production line for a resist or the like that requires submicron cleanliness.

As the resin constituting the porous film A, polyolefin, polyamide, fluorine resin and the like can be used. The thickness is preferably 5 μm to 100 μm, and particularly preferably 10 μm to 50 μm. When the film thickness is 5 μm or less, the film lacks practical strength, and defects such as pinholes are likely to occur when processed into a filter. Further, if the thickness is 100 μm or more, the area folded into the filter becomes small, and it is difficult to secure a practical processing amount.

The laminated porous membrane of the present invention is obtained by laminating a porous membrane B on the primary side of a porous membrane A. As a laminating method, techniques such as pleat processing or laminating two sheets are used.
When the average decrease rate of the flow rate at the time of solvent filtration of the laminated porous membrane is [C] and the average decrease rate of the flow rate of the porous membrane A is [A],

[0019]

[C] / [A] ≦ 1/2

## EQU1 ## That is, by laminating the porous membrane B on A, it is possible to obtain a life twice or more as long as using A alone. In addition, a differential pressure of 1 kg / c is applied to the laminated porous membrane of the present invention.
The initial flow rate of the photoresist when adding m ² and filtering the photoresist is 1700 L · cp / m ² / hr or more. The higher the flow rate, the shorter the time required for the purification of the resist, which is advantageous in terms of cost.

[0021] The laminated porous membrane according to the present invention may further comprise isopropano-
Bubble point by Le is not less 1.5 kg / cm ² or more, the rejection rate when is transmitted through the polystyrene latex having a diameter of 0.15 [mu] m, typically 85% or more, preferably 95% or more. If the bubble point or latex rejection is less than this value, it is not suitable for use in a production line for a resist or the like that requires submicron cleanliness.

Next, a method for producing a photoresist composition, which is an application of the laminated porous film of the present invention, will be described, but the application of the laminated porous film of the present invention is not limited thereto. The photoresist composition is ultraviolet, far ultraviolet, X-ray,
A composition that is sensitive to electron beams, molecular beams, gamma rays, synchrotron radiation, etc., and usually comprises an alkali-soluble resin, a radiation-sensitive compound, and a solvent.

According to the present invention, as the alkali-soluble resin, a novolak resin, a carboxyl group-containing methacrylic resin,
Known alkali-soluble resins such as polyvinyl hydroxybenzoate, styrene-maleic anhydride copolymer, and polyhydroxystyrene derivative can be used.

As the radiation-sensitive compound, 1,2-benzoquinonediazide-4-sulfonic acid ester, 1,2-naphthoquinonediazide-4-sulfonic acid ester, 1,2
Known radiation-sensitive compounds such as -naphthoquinonediazide-5-sulfonic acid ester can be used. As the solvent,
Esters such as butyl acetate, amyl acetate, ethyl lactate, methyl 1-methoxypropionate, 2-heptanone,
Examples thereof include ketones such as cyclohexanone.

Such a photoresist composition may not completely dissolve at the time of preparation, or may remain undissolved particles due to precipitation during storage. Among such undissolved particles, those having a large particle diameter hinder the use as a resist, and thus need to be removed. Therefore, if such a photoresist composition is filtered through the laminated porous membrane of the present invention, undissolved particles can be removed without reducing productivity. Naturally, foreign particles are also removed during filtration. The filtration of the resist composition is usually performed at room temperature (20
２５25 ° C.). After storage, filtration may be performed immediately before use. However, if there is a large amount of undissolved particles during storage, the particles become nuclei and precipitation is likely to be promoted. Further, the filtration may be performed only with the laminated porous membrane of the present invention, or the filtration may be performed with a coarser filter than the laminated porous membrane of the present invention and then with the laminated porous membrane of the present invention.

[0026]

EXAMPLES The present invention will be described in more detail with reference to the following Examples and Comparative Examples, which should not be construed as limiting the scope of the invention.
In addition, the measuring method in an Example is as follows. (1) Porosity The thickness t and the weight w of the film were measured and determined by the following equation. Here, the density of the resin is ρ, and the area of the measurement piece is S.

[0027]

Porosity (%) = (1−w / ρSt) × 100

(2) Bubble point This is based on JIS K3832. The measurement was performed in a constant temperature room at 23 ° C. The test solution was isopropanol (IPA). (3) Permeation rate of photoresist The pressure permeation test method according to JIS K3831 was used. The measurement was performed in a constant temperature room at 23 ° C., and the differential pressure was 1 kg / cm ² . The sample area of the porous membrane used for the test was 17.34.
cm ² .

REFERENCE EXAMPLE 1 Ultra high molecular weight polyethylene (trade name: HIZEX Million 630M, manufactured by Mitsui Petrochemical, viscosity average molecular weight: 600)
10,000), stearyl alcohol, distearylthiodipropionate, tetrakis [methylene-3- (dodecylthio) propionate] methane at 13/87 / 0.25 /
The powder blend was performed at a weight ratio of 0.25. Next, the blend was supplied to a 50 mmφ extruder whose supply part was cooled by a water-cooled jacket.
An extruder is attached and the above blend is melt-mixed at 220 ° C. to form a uniform melt. The melt was extruded from a T-die having a width of 550 mm and a die clearance of 0.4 mm, and was taken out at a draft rate of 1.5 to obtain a sheet having a thickness of 0.22 mm. From this sheet, 6
Extraction and removal with isopropanol at 0 ° C. gave a porous sheet. The residual chlorine in the sheet was less than 1000 ppm. The thickness of the porous sheet was 90 μm, the porosity was 55%, and the bubble point was 0.84 kg / cm ² .

REFERENCE EXAMPLE 2 The porous sheet obtained in Reference Example 1 was first stretched 2.0 times in the longitudinal direction of the sheet at a temperature of 100 ° C. using a roll stretching machine. -The film was stretched 3.0 times in the transverse direction at a temperature of 115 ° C. with a stretching machine. The thickness of the obtained film is 65
The porosity is 86% and the bubble point is 0.7kg /
cm ² .

Reference Example 3 Ultra-high molecular weight polyethylene (manufactured by Mitsui Petrochemical, trade name: Hizex Million 240M, viscosity average molecular weight: 2.3 million)
Powder blending was carried out in the same manner as in Reference Example 1 except that the composition ratio of styrene and stearyl alcohol was 18/82.
The mixture is supplied to an mφ extruder, and a 40 mmφ extruder is further attached to the tip of the extruder to melt and mix the blend at 210 ° C. to form a uniform melt. The melt was extruded from a T-die having a width of 550 mm and a die clearance of 0.3 mm, and was further drawn at a draft rate of 1.8 to obtain a sheet having a thickness of 0.15 mm. A porous sheet was obtained from the sheet by extracting and removing Calcol 8098 with isopropanol at 60 ° C.
The residual chlorine in the sheet was less than 1000 ppm. First, the porous sheet is put into a roll drawing machine for 100 hours.
The sheet was stretched 3.0 times in the machine direction at a temperature of 150 ° C., and then 5.5 times in the transverse direction at a temperature of 130 ° C. using a tenter stretching machine.

The thickness of the obtained film was 12 μm, the porosity was 73%, and the bubble point was 2.0 kg / cm ² . In addition, a change in the flow rate was examined by transmitting the photoresist before the final purification. The photoresist used was a novolak resin, a naphthoquinonediazide-based photosensitizer, methyl methoxypropionate as a solvent, and a viscosity of 21 c.
p, which was filtered through a 0.2 μm filter and used. The results are shown in Table 1. In addition, polystyrene latex dispersions having various particle diameters were filtered on the obtained porous membrane, and the inhibition was measured. Table 2 shows the results.

Reference Example 4 Powder blending of ultra-high molecular weight polyethylene and stearyl alcohol was carried out in the same manner as in Reference Example 3, and the blend was supplied to a 50 mmφ extruder whose supply section was cooled by a water-cooled jacket. The mixture is further melt-mixed at 210 ° C. to form a uniform melt. The melt is 550 mm wide and has a die clearance of 0.
The sheet was extruded from a 4 mm T-die and then taken out at a draft rate of 1.8 to obtain a sheet having a thickness of 0.20 mm. A porous sheet was obtained from the sheet by extracting and removing Calcol 8098 with isopropanol at 60 ° C. The residual chlorine in the sheet was less than 1000 ppm.

The porous sheet is first stretched 2.0 times in the longitudinal direction of the sheet at a temperature of 100 ° C. by using a roll stretching machine, and then horizontally stretched at a temperature of 115 ° C. by a tenter stretching machine. 4.0 in direction
Double stretching was performed. The thickness of the obtained film is 45 μm, the porosity is 81%, and the bubble point is 2.2 kg / cm ^2.
Met.

Then, the same photoresist as in Reference Example 3 was transmitted, and the change in the flow rate was examined. The results are shown in Table 1. In addition, polystyrene latex dispersions having various particle diameters were filtered on the obtained porous membrane, and the inhibition was measured. Table 2 shows the results.

REFERENCE EXAMPLE 5 The porous sheet obtained in Reference Example 1 was stretched 2.0 times in the longitudinal direction of the sheet at a temperature of 100 ° C. using a roll stretching machine. -The film was stretched 3.5 times in the transverse direction at a temperature of 115 ° C. with a stretching machine. The thickness of the obtained film is 60
The porosity is 84% and the bubble point is 1.1 kg /
cm ² .

REFERENCE EXAMPLE 6 Powder blending was carried out in the same manner as in Reference Example 3 except that the composition ratio of ultra-high molecular weight polyethylene and stearyl alcohol was 20/80. The extruder was fed to a 50 mmφ extruder, and a 40 mmφ extruder was further attached to the tip of the extruder.
Melt and mix at 10 ° C to make a uniform melt. Melt width 5
A sheet having a thickness of 0.15 mm was obtained by extruding from a T die having a die clearance of 50 mm and a die clearance of 0.4 mm, and further taking it at a draft rate of 2.3. From this sheet Calco
Extraction and removal of 8098 with isopropanol at 60 ° C. gave a porous sheet. The remaining chalcol in the sheet is 10
It was less than 00 ppm.

The porous sheet is first stretched 3.8 times in the longitudinal direction of the sheet at a temperature of 100 ° C. by using a roll stretching machine, and then horizontally stretched at a temperature of 125 ° C. by a tenter stretching machine. 8.6 in the direction
Double stretching was performed. The thickness of the obtained film is 10 μm, the porosity is 71%, and the bubble point is 3.7 kg / cm ^2.
Met.

The change in the flow rate was examined by transmitting the photoresist before final purification. The photoresist used was novolak resin, naphthoquinonediazide-based photosensitizer,
Ethyl lactate / propylene glycol methyl ether acetate is used as a solvent and has a viscosity of 20 cp. The results are shown in Table 1. In addition, polystyrene latex dispersions having various particle diameters were filtered on the obtained porous membrane, and the inhibition was measured. Table 2 shows the results.

Example 1 The porous membrane obtained in Reference Example 2 was laminated on the primary side of the porous membrane obtained in Reference Example 3. Then, the same photoresist as in Reference Example 3 was transmitted, and the change in the flow rate was examined. The results are shown in Table 1. The rate of decrease in the flow rate of the laminated porous membrane was 1/3 or less as compared with the case of Reference Example 3 in which the laminated porous membrane was not laminated. The initial flow rate of the resist was 5.20 ml / min, and the flow rate maintained 78% of the initial flow rate even after 3 hours. Table 3 shows the measurement results of the bubble point of the laminated film. The bubble point value was almost the same as when the porous membrane obtained in Reference Example 2 was not laminated.

Example 2 The same photoresist as in Reference Example 3 was applied to a laminated porous film obtained by laminating the porous film obtained in Reference Example 2 on the primary side of the porous film obtained in Reference Example 4. The permeation was performed and the change in the flow rate was examined.
The results are shown in Table 1. The rate of decrease in the flow rate of the laminated porous membrane is
The value was about 1/3 as compared with the case where no lamination was obtained in Reference Example 4.

The initial flow rate of the resist is 2.75 ml.
/ Min, and the flow rate maintained 88% of the initial flow rate even after 3 hours. Table 3 shows the results of measuring the bubble point of the laminated film. Bubble point value is Reference Example 2
This was almost the same as when the porous membrane obtained in was not laminated.

Example 3 The same photoresist as in Reference Example 6 was applied to a laminated porous film obtained by laminating the porous film obtained in Reference Example 2 on the primary side of the porous film obtained in Reference Example 6. The permeation was performed and the change in the flow rate was examined.
The results are shown in Table 1. The rate of decrease in the flow rate of the laminated porous membrane is
The value was about 1/3 as compared with the case where no lamination was obtained in Reference Example 6.

The initial flow rate of the resist is 2.51 ml.
/ Min, and the flow rate maintained 88% of the initial flow rate even after 2 hours and 20 minutes had passed. Table 3 shows the results of measuring the bubble point of the laminated film. The bubble point value was almost the same as when the porous film obtained in Reference Example 6 was not laminated.

[0045]

[Table 1]

[0046]

[Table 2]

[0047]

[Table 3]

Comparative Example 1 The porous film obtained in Reference Example 1 was laminated on the primary side of the porous film obtained in Reference Example 4, and the same photoresist as in Reference Example 3 was transmitted to check the change in the flow rate. Was. The results are shown in Table-4.

Comparative Example 2 The porous film obtained in Reference Example 3 was laminated on the primary side of the porous film obtained in Reference Example 4, and the same photoresist as in Reference Example 3 was transmitted to check the change in the flow rate. Was. The results are shown in Table-4.

Comparative Example 3 The porous film obtained in Reference Example 5 was laminated on the primary side of the porous film obtained in Reference Example 4, and the same photoresist as in Reference Example 3 was permeated to check the change in the flow rate. Was. The results are shown in Table-5.

Comparative Example 4 A commercially available porous PTFE membrane (bubble point: 0.3 kg /
cm ² , a porosity of 80%, and a film thickness of 80 μm) were laminated on the primary side of the porous film obtained in Reference Example 6 in the same manner as in Example 3, and the change in flow rate was examined by transmitting the photoresist. .
The results are shown in Table-5.

[0052]

[Table 4]

[0053]

[Table 5]

[0054]

According to the present invention, it is possible to prepare a porous membrane for a microfiltration filter which is excellent in maintaining the flow rate and has a large flow rate and excellent particle removal performance.

Claims (6)

[Claims] 1. Bubble point by isopropanol
Is 1.5kg / cm ^TwoOn the primary side of the porous membrane A described above,
The bubble point by isopropanol is 0.4-1.
0kg / cm^TwoWith a porosity of at least 60%
A laminated porous film obtained by laminating a certain porous film B. 2. When the average rate of decrease in the flow rate of the laminated porous membrane during solvent filtration is [C] and the average rate of decrease in the flow rate of the porous membrane A is [A], the following equation is obtained: [C] / [A] The laminated porous membrane according to claim 1, wherein ≤ 1/2. 3. The laminated porous membrane according to claim 1, wherein the rejection of a polystyrene latex having a diameter of 0.15 μm is 85% or more. 4. The laminated porous membrane according to claim 1, wherein the porous membrane B is made of polyethylene having a viscosity average molecular weight of 400,000 or more. 5. The initial filtration flow rate of the photoresist when filtering the photoresist at a differential pressure of 1 kg / cm ² is 170.
The laminated porous membrane according to any one of claims 1 to 4, wherein the multilayer porous membrane has a volume of 0 L · cp / m ² / hr or more and a bubble point due to isopropanol of 1.5 kg / cm ² or more. 6. A method for producing a resist composition, comprising filtering a photoresist composition liquid with the laminated porous membrane according to any one of claims 1 to 5.