HK1149088B - Film - Google Patents

Description

Film(s)

Technical Field

The present invention relates to a film for removing dust in the production of semiconductor devices, printed circuit boards, liquid crystal displays, and the like.

Background

In the manufacture of semiconductors such as LSI and super LSI, or in the manufacture of liquid crystal displays and the like, light is irradiated on a semiconductor wafer or a liquid crystal negative to form a pattern, and if dust adheres to a photomask or a reticle (hereinafter, simply referred to as "photomask") used at this time, the dust absorbs light or bends light, and thus there is a problem that the size, quality, appearance and the like are damaged, such as the pattern that has been transferred is deformed or the edge becomes rough, and the substrate is stained and blackened.

Therefore, these operations are usually performed in a clean room, and it is nevertheless difficult to keep the photomask always clean. Then, a film is attached to the surface of the photomask for dust removal, and then exposure is performed. In this case, since the foreign matter is not directly attached to the surface of the photomask but to the pellicle, the foreign matter on the pellicle is not involved in the transfer as long as the focus is made to coincide with the pattern of the photomask at the time of photolithography.

The film is a member in which a transparent film is attached to the upper end surface of the film frame. As a material of the film for a thin film, nitrocellulose, cellulose acetate, fluororesin or the like which transmits light well is used, and as a material of the film frame, aluminum, stainless steel, polyethylene or the like is used. In general, an adhesive layer made of polybutene resin, polyvinyl acetate resin, acryl resin, or the like for attaching to a photomask and a release layer (spacer) for protecting the adhesive layer are provided at the lower end of the pellicle frame.

In addition, in a state where the pellicle is attached to the photomask, for the purpose of eliminating a difference in air pressure between the space enclosed inside the pellicle and the outside, a part of the pellicle frame is provided with a vent hole for air pressure adjustment, and a filter member is provided to prevent entry of foreign matter by air moving through the vent hole (see patent document 1).

In this filter member, a plurality of vent holes are provided and a filter member is provided when a required air flow amount cannot be obtained because the vent hole for air pressure adjustment is located at one position, in general, in consideration of the collection diameter and area, to obtain the required foreign matter collection performance and air flow performance. In particular, in a large-sized liquid crystal production film having a side exceeding 500mm, in order to secure the air permeability, vent holes are usually provided at 8 to several tens of positions, and filter members are provided separately. However, providing a plurality of vent holes to ensure the ventilation amount is not preferable because it causes a reduction in the rigidity of the pellicle frame. When the rigidity is lowered, in addition to the tendency to deform during production, there is a problem that the frame is greatly bent when the film is stretched, the effective exposure area inside the film is reduced, and the film adhesion accuracy is deteriorated.

In general, a sheet-like filter member in which a porous membrane obtained by stretching Polytetrafluoroethylene (PTFE) or the like is used as a filtration membrane is often used as the filter member used herein, and such a filter member is suitable for use in a membrane in terms of cost and shape. As shown in fig. 4, the filter membrane 41 has a three-layer structure in which an adhesive layer 43 for adhering to a membrane frame is annularly disposed on one surface of the filter membrane 41, and a coarse mesh-like protective net 42 made of polypropylene (PP) or the like for protecting the filter membrane 41 is adhered to the opposite surface, and the overall thickness is about 0.15 to 0.3 mm. In order to prevent dust generation, a process of coating or impregnating an adhesive substance on a filter membrane may be performed (see patent document 2).

In this case, since the filter membrane is covered with the adhesive substance, foreign matters adhering to the filter membrane during the production of the filter member are fixed to the filter membrane and do not move in the membrane during the aeration, so that the generation of dust from the filter member is greatly reduced. The amount of the adhesive substance to be applied is determined by taking the air permeability of the filter membrane into consideration, and the dust-proof effect and the air permeability are inversely related to each other. That is, the dust-proof effect is improved as the coating amount is increased, and the air permeability is deteriorated. Therefore, it is extremely difficult to ensure high air permeability while having a high dust-proof effect.

Therefore, in particular, in a large-sized membrane, in order to ensure air permeability, it is necessary to increase the number of vent holes for air pressure adjustment, and accordingly, the number of filter members to be attached is increased. However, if the number of filter elements to be attached increases, various problems such as a burden of attachment work occur.

Generally, as shown in fig. 5, the filter member is attached to the outer surface of the membrane frame in such a manner as to cover the vent hole. If the plurality of filter members protrude outward from the film frame, the risk of damage to the filter members due to contact with the attachment/detachment jig, the film sticking apparatus, or the exposure apparatus, or the risk of wrinkles occurring in the film for the film due to the film frame being pressed inward by an amount corresponding to the thickness of the filter members, is significantly increased.

Moreover, there are manufacturing problems. The filter member needs to be well aligned and attached with tweezers or the like to prevent blocking of the vent hole. However, the filter member is generally thin, about 0.15 to 0.3mm in thickness, and it is difficult to handle the filter member because it needs to be carefully attached to prevent the membrane surface from being contaminated or damaged. Therefore, if the number of the filter members to be attached is increased, the filter member attaching operation imposes a particularly large burden on the operator.

Patent document 1: japanese Kokoku publication Sho 63-39703

Patent document 2: japanese laid-open patent publication No. 9-68792

Disclosure of Invention

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a membrane which generates less dust and has excellent air permeability, and which does not require concern about contact and breakage of a filter member during membrane treatment and has excellent handling properties during production.

The present invention relates to a membrane in which a membrane frame is provided with a through hole for adjusting an air pressure inside the membrane to be equal to an air pressure outside the membrane, and a filter member having a filter for preventing foreign matter from entering the through hole is attached to the through hole, the membrane being characterized in that the through hole includes: (1) a concave outer step portion which is opened to the outside of the membrane and accommodates the filter member; (2) a concave inner step portion opened to a bottom surface of the outer step portion; and (3) a vent hole having one end opening to the bottom surface of the inner stepped portion and the other end opening to the inside of the film (claim 1). The filter member according to the present invention is a member provided with a filter for preventing foreign matter from entering through holes, and includes a bonding layer or an adhesive layer for adhering the member to the outer step portion. The presence of the inner step portion can increase the gap below the filter surface, thereby improving air permeability. Further, by accommodating the filter member at the outer step portion, the filter member does not protrude from the outer surface of the membrane frame or the protruding degree is reduced, and the risk of contact and damage of the filter member during membrane treatment is extremely reduced. Further, since the outer stepped portion is also a target of the attachment position when the filter member is attached, the outer stepped portion can be attached at an accurate position without any special technique.

Here, the depth of the outer step portion is preferably in the range of 50 to 150% of the thickness of the filter member (claim 2). The thickness of the filter member includes the thickness of a bonding layer or an adhesive layer for adhering the filter member to the bottom of the outer step portion. If the depth of the outer step portion is at least 50% of the thickness of the filter member, some effect of reducing the risk of breakage of the filter member and the alignment effect at the time of attachment can be obtained. However, if the depth is too deep relative to the thickness of the filter member, the adhesion workability is greatly reduced, so the upper limit thereof is preferably 150%.

Preferably, the area of the opening of the inner stepped portion on the outer stepped portion side is in the range of 80 to 150% of the ventilation area of the filter member, and the depth of the inner stepped portion is 0.2mm to 1mm (claim 3). This range is preferable as the space under the filter surface. Here, the ventilation area of the filter means an area involved in ventilation of the filter, and for example, in the case of a filter member in which an adhesive layer for bonding to a membrane frame is arranged in a ring shape on the filter, the area surrounded by the ring-shaped adhesive layer is a ventilation area.

In addition to the above, when an adhesive substance is applied or impregnated to the filter of the filter member (embodiment 4), the occurrence of dust from the filter member can be remarkably reduced while ensuring air permeability. Since the presence of the inner step portion can increase the space under the filter surface, when the adhesive substance is applied or impregnated from the outside of the filter, the adhesive substance oozed out to the inside of the filter is prevented from staying on the ventilation surface of the filter or from adhering to the inner surface of the through hole, and a desired ventilation performance can be obtained.

The effects of the present invention are as follows.

According to the present invention, since the ventilation area of the filter is secured to the maximum extent by providing the inner stepped portion, the number of the ventilation holes can be reduced, and the diameter of the ventilation holes can be reduced. As a result, the reduction in rigidity of the pellicle frame due to the provision of the through-holes can be minimized. Further, even when an adhesive substance for reducing the generation of dust is applied or impregnated on the filter, the presence of the inner step portion ensures air permeability and a film having both high air permeability can be obtained. Further, since the filter member is mounted in the outer step portion, the filter member does not protrude from the surface of the membrane frame or protrudes less, and contact and breakage between the filter member and the membrane frame during use when the membrane is attached are reduced, thereby providing a highly reliable membrane. Moreover, since the filter member can be easily aligned during production, the workability is greatly improved, and the filter member can be handled in a short time with high reliability even when a plurality of filter members are attached.

Drawings

FIG. 1 is a main part view of a first embodiment of the film of the present invention, (A) is a front view, and (B) is a sectional view taken along the line I-I.

FIG. 2 is a main part view of a second embodiment of the film of the present invention, wherein (A) is a front view and (B) is a sectional view taken along the line I-I.

FIG. 3 is a main part view of a third embodiment of the film of the present invention, wherein (A) is a front view and (B) is a sectional view taken along the line I-I.

Fig. 4 is a structural view of an example of the filter member, where (a) is a top view, (B) is a front view, and (C) is a bottom view.

FIG. 5 is a partial view of a conventional film, wherein (A) is a front view and (B) is a cross-sectional view taken along line I-I.

Fig. 6 is a view for explaining a case where an adhesive substance is applied or impregnated.

FIG. 7 shows a pellicle frame, where (A) is a top view and (B) is a cross-sectional view taken along line I-I.

FIG. 8 shows an apparatus for evaluating air permeability.

Fig. 9 is a generated dust evaluation device.

In the figure:

11-membrane frame, 12-vent hole, 13-membrane bonding layer, 14-membrane, 15-mask, 16-outside step, 17-inside step, 18-filter member, a, b, c-outside step size, c, d, f-inside step size, g-diameter of vent hole, h-corner radius of curvature of outside step, k-corner radius of curvature of inside step, 21-membrane frame, 22-vent hole, 23-membrane bonding layer, 24-membrane, 25-mask adhesive layer, 26-outside step, 27-inside step, 28-filter member, 31-membrane frame, 32-vent hole, 33-membrane bonding layer, 34-membrane, 35-mask adhesive layer, 36-outer step, 37-inner step, 38-filter member, 38 a-filter, 38 b-outer tube, 38 c-adhesive layer, 41-filter membrane, 42-protective net, 43-adhesive layer, 51-membrane frame, 52-vent, 53-membrane bonding layer, 54-membrane film, 55-mask adhesive layer, 56-filter member, 61-membrane frame, 62-vent, 63-filter membrane, 64-protective net, 65-adhesive layer, 66-coated adhesive substance, 67-outer step, 68-inner step, 71-membrane frame, 81-base plate, 82-vent and air introduction valve, 83-support frame, 84-ultrasonic distance sensor, 85-display gauge, 86-film, 91-quartz glass substrate, 92-film, 93-filter, 94-air gun.

Detailed Description

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited thereto. The present invention is particularly effective in a large-sized thin film (ペリクル) having a length of one side exceeding 500mm used in liquid crystal production applications where the number of through holes is large, but the present invention is not particularly limited in its application since a desired effect can be obtained even when applied to a small-sized thin film having a number of through holes of about 1 to 2 used in semiconductor applications.

The film frame is provided with a through hole. The through hole includes an outer step portion, an inner step portion one turn smaller than the outer step portion, and a vent hole, the outer step portion one turn larger than the filter member, and the filter member is attached to be accommodated in the outer step portion.

Since the filter member does not protrude or protrudes less toward the surface of the membrane frame, the risk of the filter member coming into contact with and peeling off or falling off when the membrane is handled is greatly reduced. Further, although the filter is usually attached using tweezers or the like, since the outer step portion is a target for attachment, alignment is extremely easy and operability is greatly improved. In the case where there is no outer step portion, it is necessary to adjust the position so that the center of the filter ventilation surface, which is not visible from the outside of the filter, is substantially directly above the ventilation hole, which is very difficult to handle.

The depth of the outer step portion to which the filter member is attached is preferably in the range of 50 to 150%, more preferably 100 to 120%, of the thickness of the filter member. If the amount is 100% or less, the filter member protrudes, and therefore, the risk of breakage of the filter member cannot be completely avoided, but the alignment is easy during manufacturing. The depth of the outer step portion is over 150% of the depth of the filter member, which is disadvantageous in that the cleaning property is deteriorated and the workability is deteriorated in the attachment operation of the filter member.

Since the space below the ventilation surface of the filter can be sufficiently secured by the inner stepped portion, the ventilation property of the filter member is improved. In particular, when an adhesive substance is applied to or impregnated into the filtration membrane, a great effect is exhibited.

Fig. 6 shows the state of the adhesive substance when the adhesive substance is applied or impregnated on the filter. The adhesive substance 66 that has oozed out to the inside of the filter membrane 63 is aggregated on the side walls of the adhesive layer 65 and the inside step portion 68 by surface tension. As a result, the adhesive substance can be prevented from staying on the air-permeable surface of the filtration membrane 63 or from adhering to the membrane frame 61, and therefore, the reduction in the air-permeable area of the filtration membrane 63 hardly occurs. Thus, the decrease in air permeability due to the adhesive substance can be minimized. Fig. 6 shows the case where a filtration membrane is used, but the same state is also obtained in the case of a filter having a shape other than the membrane.

Since the air vent has a smaller influence on the air permeability than the filter, the shape of the air vent is determined mainly by considering the influence on the rigidity of the film frame and the workability. In the present invention, the shape of the vent hole is not particularly limited, but the circular hole is preferable in view of workability. The larger the diameter, the easier the processing, but the larger the diameter, the lower the rigidity of the pellicle frame, so that the smaller the diameter, the more preferable the diameter is, in order to ensure the air permeability. In view of air permeability, a diameter of about 0.5mm is sufficient, but in the case of a particularly large pellicle such as one having a pellicle frame width of more than 10mm, a blade having a small diameter is bent and the processing speed is extremely slow, and therefore, a diameter of about 1.5mm is most preferable in view of high production efficiency of drilling.

Even if the vent hole is formed to have an extremely large diameter or a cross-sectional shape similar to that of the vent surface of the filter instead of the inner stepped portion, the same effect as that of the present invention can be obtained. However, in these methods, as described above, the film frame rigidity is significantly reduced due to the reduction in the cross-sectional area of the film frame, and thus the film frame is not durable. In the method of the present invention, the reduction of the cross-sectional area of the pellicle frame can be minimized, and there is little adverse effect on the rigidity of the pellicle frame.

The area of the opening of the inner step portion on the outer step portion side is preferably in the range of 80 to 150% of the ventilation area of the filter member, and the depth of the inner step portion is preferably 0.2mm to 1 mm. If the content is 80% or less, the ventilation surface of the filter cannot be sufficiently secured, and if the content is 150% or more, the number of bonding portions of the adhesive layer decreases, and the reliability of mounting decreases. Further, if the depth is 0.2mm or less, contact with the filter surface cannot be completely eliminated, and if the depth is 1mm or more, the cleaning performance is deteriorated, and inspection of foreign matter in the step portion is difficult, which is not preferable.

The shape of the inner stepped portion is preferably designed appropriately in consideration of workability, detergency, and the like in addition to the above range. In addition to the shapes shown in fig. 1 to 3 described later, a shape in which one or more steps are provided on the wall surface of the inner stepped portion may be adopted.

Fig. 1 shows a first embodiment of the film of the present invention. Fig. 1 is a partial view showing the periphery of a filter member mounting portion, and the filter member has a structure as shown in fig. 4, in which an adhesive layer 43 is bonded to one surface of a filter membrane 41 made of porous PTFE or the like, and a net such as PP having a large mesh is bonded to the opposite surface thereof as a protective net 42. The central region of the adhesive layer 43 is hollowed out, and this region is exposed to the filtration membrane 41, so that ventilation is performed using this region. The inner step 17 is cut at a corner at the bottom thereof at a right angle. The shape of the opening on the outer stepped portion side of the inner stepped portion in the planar direction matches the exposed shape of the filter member.

Fig. 2 shows a second embodiment of the film of the present invention. In the dotted line in fig. 2(a), the outer dotted line indicates the inner peripheral surface of the filter membrane adhesive layer, and the inner dotted line indicates the shape of the opening of the inner step portion 27. In this embodiment, the corner portion of the bottom of the inner stepped portion 27 is formed into an R-shape, and the shape of the opening portion on the outer stepped portion side of the inner stepped portion in the planar direction is formed into a rounded shape which is easy to machine.

Fig. 3 shows a third embodiment of the film of the present invention. Although the case of using the filter member having the single-layer filter membrane shown in fig. 4 has been described above, a cylindrical filter member 38 shown in fig. 3 may be used. The cylindrical filter member 38 is attached by caulking or joining a filter 38a made of a sintered metal porous body, porous ceramic, stainless steel wire, porous resin or the like in an outer cylinder 38b made of stainless steel, polypropylene or the like, and is provided with an adhesive layer 38c for fixing to the membrane frame 31, and the filter member 38 is ventilated between both end faces of the cylinder. Fig. 3 shows a structure without a protective net, but a protective net may be provided. A bonding agent layer may be provided instead of the adhesive layer 38 c. In this case, if the inner stepped portion 37 of the recess of the other stage is provided further inside the recess of the outer stepped portion 36 accommodating the filter member, the same effect as that in the case of the filter member of the single-layer film described above can be obtained. It is preferable that the gap between the outer tube 38b and the outer stepped portion 36 is filled with a bonding material such as epoxy or silicone resin.

Examples

The following describes embodiments of the present invention, but the present invention is not limited to these descriptions.

Example 1

A rolled plate of A5052 aluminum alloy was machined to form a pellicle frame having an outer dimension of 1526X 1748mm, an inner dimension of 1493X 1711mm, and a height of 6.2mm as shown in FIG. 7. The pellicle frame was provided with through-holes at 16 positions, and each through-hole had a cross-sectional shape as shown in fig. 1 (B). Here, in terms of the dimensions in the drawing, the outer step (a, b, e) is 10 · 4.0 × 0.3mm, the inner step (c, d, f) is 7.5 × 1.6 × 0.5mm, the vent hole diameter g is 1.5mm, the radius of curvature h of the outer edge corner of the outer step is 1.0mm, and the radius of curvature k of the outer edge corner of the inner step is 0.5 mm. After the machining, the surface of the pellicle frame was subjected to a sand blast treatment and then to a black alumite treatment.

The pellicle frame was carried into a class 100 clean room, washed with a surfactant and pure water, and completely dried.

Then, a silicone adhesive (trade name KR3700, manufactured by shin-Etsu chemical Co., Ltd.) was diluted with toluene as a film adhesive 13 for a film and applied to the upper end surface of the film frame so that the dry film thickness was about 100. mu.m. A silicone adhesive (trade name KR3700, manufactured by shin-Etsu chemical Co., Ltd.) was diluted with toluene and applied to the lower end face to have a width of 6mm as a mask adhesive constituting the mask adhesive layer 15. At this time, finishing was performed so that the height of the adhesive after drying was about 2 mm.

Then, a filter member having a trapping diameter of 0.1 μm, which was prepared by punching and which was composed of a protective mesh 42, a filter membrane 41, and an adhesive layer 43 as shown in FIG. 4, was stuck to each vent hole using tweezers, and then a silicone adhesive (trade name KR3700, manufactured by shin-Etsu chemical Co., Ltd.) was diluted with toluene to an appropriate viscosity and applied to 4 μ l from the surface of the filter member with a hand dispenser to impregnate the adhesive into the filter membrane. The time required for the operation of sticking the filter using tweezers was measured, and as a result, it took about 15sec for each sheet.

Then, the pellicle frame is heated to 130 ℃ to dry the solvent in the adhesive or bonding agent and to completely crosslink the silicone adhesive, and then a separator separately prepared as a protection of the adhesive is bonded to the mask adhesive layer 15. The separator was produced by cutting a polyethylene terephthalate (PET) film (having a thickness of 125 μm and being translucent) coated with a release agent on one surface into a film frame shape.

Next, the production of the film for a thin film will be described. After cleaning and drying a quartz substrate having a smooth polished surface of 1620X 1780mm in a clean room of class 100, a solution of a fluororesin (manufactured by Asahi glass company, Ltd.; trade name サイトツプ) was coated on one surface thereof as a film material by a metal-type coating method so that the film thickness after drying became 6 μm. The film forming method uses a metal coating method, but various methods such as a spin coating method, a slit method, and a spin method may be used in addition to this method. Then, each film formation substrate was heated to 200 ℃ in an oven to dry the solvent. After cooling, the frame-shaped film peeling jig was gradually peeled off from the substrate to obtain a film for a thin film.

Finally, the film for the thin film in a state of being bonded to the film peeling jig is bonded to the film bonding layer of the film frame, and the remaining film on the outer side is cut off by a cutter to complete the thin film.

When the appearance of the filter unit of the completed membrane is observed, all the filters are accommodated in the step difference, and the structure is optimized without bending or deflection.

Then, the film was evaluated for air permeability. Fig. 8 shows an apparatus used for evaluation. The film to be measured 86 is bonded to an aluminum base plate 81, and a valve 82 for introducing air into the film is provided. An ultrasonic distance sensor 84 is attached to the base plate 81 at a predetermined distance from the base plate and below the support frame 83, and the distance to the film for film can be measured and displayed on the display 85.

In this apparatus, 5000cc of air was introduced into the film, and when the time taken for the film to return to the original height was measured, the time was 17 hours and 30 minutes.

Then, the amount of dust generated from the filter member was evaluated for the film. First, a quartz glass substrate having a polished surface of 1620 × 1780 × 10mm in thickness was prepared, cleaned and dried in a clean room, and then inspected for foreign matter on the substrate using a spotlight in a dark room. The foreign matter adhering thereto is removed by air blowing, and the position thereof is accurately recorded in the map for the foreign matter that cannot be removed.

Then, as shown in fig. 9, the produced thin film 92 was bonded to the quartz glass substrate 91, and a closed space surrounded by the thin film 92 and the glass substrate 91 was produced. Then, the filter part 93 of the film 92 is randomly selectedAt point 5, air was blown from the outside with an air gun 94. The blowing conditions were set to 2mm in nozzle diameter, 20mm in distance and 4kgf/cm in pressure²Blowing time 10 sec.

After the air blowing was performed on the filter member, the foreign matter on the quartz glass substrate 91 was visually inspected by a spotlight in a dark room, and compared with the inspection map before the air blowing. As a result, no foreign matter was increased on the substrate, and it was confirmed that no dust was generated from the filter member.

Example 2

A thin film was produced by the same method and procedure as in example 1. However, the filter member used was not coated with a silicone adhesive. The film was subjected to appearance inspection and evaluation of air permeability in the same manner as in example 1.

When the appearance of the filter element of the completed membrane was observed, all the filter elements were accommodated in the step difference, and an optimum structure without bending and deflection was obtained.

For the air permeability evaluation, 5000cc of air was introduced into the film by using the apparatus of FIG. 8, and the time taken for the film to return to the original height was measured, and the time was 14h40 min.

Comparative example 1

A rolled plate of A5052 aluminum alloy was machined to form a pellicle frame having an outer dimension of 1526X 1748mm, an inner dimension of 1493X 1711mm, and a height of 6.2mm as shown in FIG. 7. The pellicle frame was provided with 16 vent holes 52 having a diameter of 1.5mm and a cross-sectional shape having the same diameter as that shown in fig. 5, and after the machining was completed, the surface of the pellicle frame was subjected to sand blasting and then black alumite treatment.

Then, the pellicle frame was cleaned and dried in a class 100 clean room in the same manner as in example 1, and then coated with a film bonding agent 53 and a mask adhesive 55 in the same manner as in example 1. Then, after the filter member having the structure shown in FIG. 4 prepared by punching was stuck to each vent hole using tweezers, a silicone adhesive (product name KR3700, manufactured by shin-Etsu chemical Co., Ltd.) was diluted with toluene to the same viscosity as in example 1 and applied by a hand dispenser so as to be 4. mu.l from the surface of the filter member 56, and the adhesive was impregnated into the filter membrane. At this time, the time required for the operation of sticking the filter using tweezers was measured, and as a result, about 36sec was required on average for each sheet.

Thereafter, the pellicle frame was heated to 130 ℃ to dry the solvent, and the silicone adhesive was completely crosslinked, and a spacer separately prepared as a protective adhesive was bonded to the mask adhesive layer.

Finally, the film for a thin film prepared in the same manner as in example 1 was attached to the film bonding layer of the film frame, and the remaining film outside the film frame was cut off by a cutter to complete the thin film.

The resultant film was evaluated for air permeability using the apparatus shown in fig. 8 in the same manner as in example 1. 5000cc of air was injected from the air introducing valve 82 into the closed space of the film, and then the time until the film returned to the horizontal was measured, and as a result, the time was about 41 hours.

For the completed film, the appearance of the filter element was observed. The deflection and curvature is seen on the individual filter elements, in particular the deflection of the spacing of the individual filter elements is significant. The spacing between the individual filter elements was measured and as a result, the filter elements were mounted at a minimum of 78mm and a maximum of 83mm for a design 80mm spacing. If the filter member is attached while being displaced from its original position, the silicone adhesive applied to the filter member may flow directly into the vent hole, which may narrow or block the vent hole due to the adhesive layer, and this may occur in the film. Further, the appearance is also not beautiful. In addition, since 16 filter members protrude from the membrane frame, the risk of breakage or peeling when the membrane frame is contacted for some reason is very high.

Further, as an evaluation of the amount of dust generated from the filter member, the filter member at 5 was subjected to air blowing under exactly the same conditions as in example 1, but the foreign matter on the substrate was not increased at all, and generation of dust from the filter member was not confirmed.

When the above results were summarized in comparative example 1, the effect of the adhesive applied to the filtration membrane was very good in that no dust was generated from the filter member, but the appearance of the filter member in the stuck state was poor and the air permeability was very poor. The performance was very poor compared with example 1.

Comparative example 2

A thin film was produced by the same method and procedure as in comparative example 1. However, the filter member used was not coated with a silicone adhesive. This film was evaluated in exactly the same manner as in example 1.

The appearance of the filter part of the completed membrane was largely curved and deviated as in comparative example 1, and the surface was not beautiful.

For the air permeability evaluation, 5000cc of air was introduced into the film by using the apparatus of FIG. 8, and the time taken for the film to return to the original height was measured, and the time was 15h30 min.

Further, as an evaluation of the amount of dust generated from the filter member, air blowing was performed on the filter member at 5 under exactly the same conditions as in example 1 described above. As a result, it was found that several foreign matters having a diameter of 5 to 30 μm were attached to the glass substrate in the vicinity of the vent hole at 4 out of 5.

In summary, the film of comparative example 2 was inferior to the film of example 2 in air permeability. Moreover, the dust generated from the filter is large, and the reliability is very low.

Claims (5)

1. A membrane in which a membrane frame is provided with a through hole for adjusting the pressure inside the membrane to be equal to the pressure outside the membrane, and a filter member having a filter for preventing foreign matter from entering the through hole is attached to the through hole,

the through-hole includes:

(1) a concave outer step portion which is opened to the outside of the membrane and accommodates the filter member;

(2) a concave inner step portion opened to a surface of the outer step portion adjacent to the inside of the film; and

(3) a vent hole having one end opening to the surface of the inner stepped portion near the film interior and the other end opening to the film interior,

the inner step is smaller than the outer step.

2. The film of claim 1,

the depth of the outer step is in the range of 50-150% of the thickness of the filter member.

3. The film according to claim 1 or 2,

the area of the opening of the inner step portion on the outer step portion side is in the range of 80-150% of the ventilation area of the filter member, and the depth of the inner step portion is 0.2mm to 1 mm.

4. A film according to claim 3,

the filter of the filter member is coated or impregnated with an adhesive substance.

5. The film according to claim 1 or 2,

the filter of the filter member is coated or impregnated with an adhesive substance.