JP6842879B2 - Polyolefin-based film with excellent uniform expandability and resilience - Google Patents

Description

The present invention is easy to expand uniformly in all directions such as vertical direction, horizontal direction, diagonal direction, etc., and when tension is removed after expansion, it can be restored to almost the original shape. Regarding excellent polyolefin-based films.

A semiconductor wafer made in a large area in advance is subjected to a back grind process in which it is polished and thickness-adjusted as necessary, and then attached and fixed to a dicing film set on a ring frame to form a chip. It is mounted on a predetermined base through a dicing step of being cut, an expanding step of separating each chip by expanding (expanding) the dicing film, a pick-up step of picking up each chip, and the like.

Since the semiconductor wafer of the dicing film is cut on the film, there is a risk that the dicing film will be scratched by a cutting tool or the like. Therefore, the film is required to have a property of being hard to tear even if it is scratched. Further, the dicing film is often used not only in the dicing step but also in the expanding step which is the next step. In the expanding step, in order to form an even gap between the chips, the dicing film has the property of uniformly expanding in all directions such as the vertical direction, the horizontal direction, and the diagonal direction (hereinafter referred to as uniform expandability). Is required.
Further, in recent years, the dicing step and the expanding step may be performed by using another film for a semiconductor manufacturing process. In this case, the film for the semiconductor manufacturing process (dicing film) used in the dicing process is not required to have uniform expandability, but the film for the semiconductor manufacturing process (expanded film) used in the expanding process is required to have uniform expandability. ..

The dicing film after expansion (expanded film when the dicing process and the expanding process are performed using different process films) is set in the ring frame, and the slack due to the expansion is removed by heating, and the storage rack. Stored in. At this time, if the slack is not sufficiently removed, the storage in the storage rack will not be successful and cause trouble. Therefore, these films are also required to have the property of being able to remove slack after expansion.

Patent Document 1 is an invention relating to a polyolefin-based film having excellent uniform expandability and the like. Conventionally, soft PVC films have been used for applications that require uniform expandability, but soft PVC films have problems with the safety of plasticizers and stabilizers, problems with their bleed-out, and gas generated during combustion. There are problems such as. Against the background of such problems, Patent Document 1 has an object of providing a polyolefin-based film having excellent uniform expandability and the like.

According to Patent Document 1, the uniform expandability of the film is closely related to the in-plane retardation, the in-plane retardation of the film before stretching is R ₀ , and the film is 50% in the vertical direction and the horizontal direction at the same time. It is disclosed that a film having R ₀ ≤ 300 nm and R ₅₀ / R ₀ of 2.00 or less is excellent in uniform expandability when the in-plane phase difference after stretching is R _{50 (Patent Document 1).} [0008]). Further, Patent Document 1 describes that R ₀ and R ₅₀ / R ₀ depend on the film manufacturing conditions (Patent Document 1 [0009]).
Note that Patent Document 1 does not describe anything about removing slack after expanding.

Patent Document 2 is an invention relating to a dicing film that does not easily loosen after expansion. Conventionally, the expanded dicing film is stored in a storage rack after its slack is removed by heating. However, the dicing film of Patent Document 2 is excellent in rack recoverability because it recovers 90% or more only by removing the tension in the expanding step without heating (Patent Document 2 [0010]).
The dicing film of Patent Document 2 is assumed to be used when the expanding rate in the expanding step is low (Patent Document 2 [0005]), and the stability evaluation in the examples is based on the original shape. The restoration rate after stretching by 20% is obtained (Patent Document 2 [0064]). Therefore, it seems that there is a problem in using it in a general expanding process (stretching of about 40%).

Japanese Unexamined Patent Publication No. 2001-232683 Japanese Unexamined Patent Publication No. 2009-105236

An object of the present invention is to provide a polyolefin-based film having excellent uniform expandability and resilience. Specifically, it is a polyolefin-based film preferably used as a base film for a process film (dicing film or expanded film) used in an expanding process in a semiconductor manufacturing process, and is used in all directions such as a vertical direction, a horizontal direction, and an oblique direction. It is an object of the present invention to provide a polyolefin-based film that easily expands uniformly in a direction and can be restored to its original shape by removing the tension after stretching even if it is stretched by 40% or more.

The present inventors have diligently studied to solve the above problems, and are a random copolymer of propylene and ethylene and / or an α-olefin having 4 to 8 carbon atoms, and are ethylene and / or 4 to 8 carbon atoms. It was found that the propylene-based random copolymer having a high content of α-olefin and a low density has a lower crystallinity than a general random copolymer and is excellent in uniform expandability and restorability. However, at the same time, it has also been found that the resin has a problem in film formation stability and it is difficult to continuously form a film. Then, they have found that the above-mentioned problems can be solved by using the above-mentioned propylene-based random copolymer having low crystallinity as a base layer and providing a surface layer for improving film-forming property.

That is, according to the present invention, as a means for solving the above problems,
A polyolefin-based film having at least a surface layer (A) and a base layer (B), wherein the base layer (B) is a random copolymer of propylene and ethylene and / or an α-olefin having 4 to 8 carbon atoms. A propylene-based random copolymer (β) having a content of ethylene and / or an α-olefin having 4 to 8 carbon atoms of 6% by weight or more and a density of 885 kg / m ^{3 or less measured according to ASTM D1505.} Provided is a polyolefin-based film having excellent uniform expandability and resilience, which is characterized by containing
Further, the surface layer (A) contains less ethylene and / or α-olefin having 4 to 8 carbon atoms than the propylene-based random copolymer (β), and has a higher density than the propylene-based random copolymer (β). Provided is a polyolefin-based film having excellent uniform expandability and restorability, which is characterized by containing α) as a main component.

Further, the propylene-based random copolymer (α) and / or the propylene-based random copolymer (β) is a propylene-ethylene random copolymer, which is excellent in uniform expandability and restorability. Polyolefin-based films are provided
Further, there is provided a polyolefin-based film having excellent uniform expandability and restorability, wherein the surface layer (A) contains 3% by weight or more and less than 50% by weight of a crystalline olefin-based resin.
Further, when the thickness of the polyolefin-based film having excellent uniform expandability and resilience is t, the thickness of the surface layer (A) is tA, and the thickness of the base layer (B) is tB, 6 μm ≦ tA, 0. A polyolefin-based film having excellent uniform expandability and resilience, which is characterized in that 50 t ≦ tB.

Further, the polyolefin-based film is characterized by having both the restoration rate Rmd in the film flow direction and the restoration rate Rtd in the film width direction measured by the following restoration rate measurement method being 90% or more. And a polyolefin-based film having excellent resilience is provided.
[Recovery rate measurement method]
A film piece having a length of 150 mm and a width of 10 mm is cut out so that the direction to be measured is the vertical direction, and two lines are inserted in the central portion in the vertical direction so that the distance between the scores is 50 mm to prepare a test piece. This test piece is set in a tensile tester set to a chuck-to-chuck distance of 70 mm so that the center lines of the two lines are at the center between the chucks, and 40% (chuck-to-chuck distance) at a tensile speed of 200 mm / min. The film is stretched (until it reaches 98 mm), held in that state for 300 seconds, and then the chuck is opened and the test piece is taken out. When the shape of the test piece is stable, the distance L between the scores is measured, and the restoration rate is calculated by the formula (1).
Restoration rate (R) = (50 / L) x 100 ... Equation (1)

Further, in the polyolefin-based film, the distance Nmd between the five grades in the film flow direction and the distance Ntd between the five grades in the film width direction measured by the following necking measurement method are all within 14 mm ± 1 mm. Provided is a polyolefin-based film having excellent uniform expandability and resilience.
[Necking measurement method]
Cut out a film piece of 150 mm in length × 10 mm in width so that the direction you want to measure is the vertical direction, insert two lines in the center part in the vertical direction so that the distance is 50 mm, and between the two lines Make a test piece by marking four points so that the distance is 10 mm. This test piece is set in a tensile tester set to a chuck-to-chuck distance of 70 mm so that the center lines of the two lines are at the center between the chucks, and 40% (chuck-to-chuck distance) at a tensile speed of 200 mm / min. The film is stretched (until 98 mm), and with the film stretched, the distance N between the five scores formed by the two lines and the four points is measured.

Further, a film for a semiconductor manufacturing process, characterized in that a polyolefin-based film having excellent uniform expandability and resilience is used as a base film, has been provided.
Further, there is provided the film for a semiconductor manufacturing process, wherein at least one surface layer (A) of the base film contains an antistatic agent.

The polyolefin-based film of the present invention is a propylene-based random copolymer (hereinafter, r) having a high content of ethylene and / or α-olefin having 4 to 8 carbon atoms (hereinafter, referred to as a comonomer if necessary) and a low density. Since it has a base layer containing (β) as a main component (abbreviated as −PP), it is excellent in uniform expandability and restorability. Further, since the surface layer (A) is provided on at least one surface, stable film formation can be performed. In particular, when the surface layer (A) contains r-PP (α) having a lower content of comonomer and a higher density than r-PP (β) as a main component, or when the surface layer (A) contains 3 crystalline polyolefin resins. When the content is ~ 48% by weight, a stable film can be formed while maintaining a high restoration rate.
A polyolefin-based film (hereinafter referred to as elastic film) having excellent uniform expandability and recoverability according to the present invention, which has a recovery rate of 90% or more after stretching by 40% in both the flow direction and the width direction of the film. Is suitable as a process film for semiconductor manufacturing such as a dicing film and an expanded film.

Hereinafter, the elastic film of the present invention will be described in detail, focusing on the case where the film is used as a base film for a dicing film. However, the elastic film of the present invention is not limited to the following.

[Base layer (B)]
The elastic film of the present invention comprises a surface layer (A) for ensuring film-forming property and a base layer (B) for ensuring uniform expandability and resilience. The base layer (B) is a polyolefin resin having low crystallinity, specifically r-PP (β) having a comonomer content of 6% by weight or more and a density measured according to ASTM D1505 of 885 kg / m ^{3 or less.} Main component. If the content of the comonomer is less than 6% by weight, or the density of the copolymer (β) ^{exceeds 885 kg / m 3} , the crystallinity of r-PP (β) becomes high, so that the uniform expandability of the elastic film and the uniform expandability Restorability is reduced. The comonomer component can be appropriately selected from ethylene and α-olefin having 4 to 8 carbon atoms, but ethylene is particularly suitable in consideration of stability.

The content of the comonomer is 6% by weight or more, particularly preferably 10% by weight or more, and further preferably 12% by weight or more. The higher the content of comonomer, the better the uniform expandability and resilience of r-PP (β). However, if the content of the comonomer becomes too high, the rigidity and heat resistance of the base layer (B) may be significantly reduced. From this point of view, it is desirable that the content of the comonomer is less than 40% by weight, particularly less than 30% by weight, further less than 25% by weight, and particularly less than 20% by weight.
The density of the r-PP (β) is preferably less than 875kg / m ^3, in particular less than 870 kg / m ³ is, among others less than 865kg / m ³ are preferred. In the above range of comonomer content, the lower the density, the lower the crystallinity of r-PP (β), and the better the uniform expandability and restorability of the obtained film.
Further, the melting point of r-PP (β) is preferably 75 ° C. or higher, particularly preferably 100 ° C. or higher, from the viewpoint of heat resistance.

As the r-PP (β) used in the present invention, a commercially available one can be appropriately selected and used. For example, in the product name "Vistamax (registered trademark)" manufactured by ExxonMobil, the product name "Versify (registered trademark)" manufactured by Dow Chemicals, and the product name "Toughmer (registered trademark) PN" manufactured by Mitsui Chemicals. Some grades correspond to r-PP (β).
Among them, ExxonMobil's "Vistamax" is a copolymer of propylene and ethylene rich in amorphous content, has an isotactic polypropylene crystalline region and an amorphous region, and has uniform expandability and restorability. Especially excellent in.

The base layer (B) may contain other subcomponents as long as it contains the above-mentioned r-PP (β) as a main component (in other words, if it contains 50% by weight or more of r-PP). .. The sub-component is not particularly limited, but a resin having excellent compatibility with r-PP (β), which is the main component, and which does not negate the properties of the resin is desirable. However, the lower the content of r-PP (β) in the base layer (B), the lower the uniform expandability and resilience of the elastic film may be. Therefore, the content of r-PP (β) in the base layer (B) is preferably 70% by weight or more, particularly preferably 85% by weight or more, and further preferably 95% by weight or more.
In addition, for the base layer (B), two or more kinds of r-PP (β) having slightly different content and density of comonomer can be blended and used. In this case, the total sum of each r-PP (β) is set to 50% by weight or more.

Further, as long as it does not interfere with the object of the present invention, the base layer (B) is appropriately provided with various additives such as an antistatic agent, an antifogging agent, and an antioxidant for the purpose of providing each effective action. Can be used. However, it is desirable not to add lubricants or blocking inhibitors. Since the film-forming property of the film is ensured by the surface layer (A) described later, it is not necessary to add a lubricant or an anti-blocking agent. When the elastic film of the present invention is used as a base film for a film for a semiconductor manufacturing process, addition of a lubricant or an anti-blocking agent may contaminate the semiconductor.

[Surface layer (A)]
The above-mentioned base layer (B) is excellent in uniform expandability and excellent resilience, but it is difficult to form a stable film because it easily expands and contracts. The film formed by the inflation extrusion method or the T-die extrusion method comes into contact with a large number of rolls before being wound up, but the above-mentioned r-PP (β) has poor peelability from each roll. Further, normally, the tension of the film between the rolls is controlled to be constant and the film is conveyed, but the film made of r-PP (β) stretches greatly even with a weak tension, so that it is difficult to control by the tension. .. Therefore, the elastic film of the present invention includes a surface layer (A) that supplements the film-forming property of the base layer (B).

The resin composition of the surface layer (A) is not particularly limited as long as the adhesion to the roll is lower than that of the base layer (B) and the film-forming property of the base layer (B) can be supplemented. A resin composition containing r-PP (α) as a main component, which has a lower comonomer content and a higher density than PP (β), can be exemplified as a suitable one. r-PP (α) is less likely to generate gel than a thermoplastic resin containing ethylene as a main component, and can improve film formation without lowering the uniform expandability and resilience of the base layer (B). it can.
The comonomer content in r-PP (α) is preferably 4% by weight or more, and particularly preferably 6% by weight or more. Since r-PP having a low comonomer content has too high crystallinity, the obtained film tends to cause necking, it is difficult to spread it uniformly, and the restoration rate tends to be low. The comonomer component in r-PP (α) is preferably 15% by weight or less, particularly preferably 12% by weight or less, and further preferably 8% by weight or less from the viewpoint of film forming property.

Such r-PP (α) is the above-mentioned product name "Vistamax (registered trademark)" manufactured by ExxonMobil, product name "Versify (registered trademark)" manufactured by Dow Chemicals, and product manufactured by Mitsui Chemicals. From the name "Toughmer (registered trademark) PN", a grade having a low ethylene content and a high density can be selected and used.
The difference in comonomer content between r-PP (α) and the above-mentioned r-PP (β) is not particularly limited, but is preferably 3% or more, and particularly preferably 6% or more.

Further, by adding 3% by weight or more and less than 50% by weight, preferably 3 to 48% by weight, and more preferably 15 to 35% by weight of the crystalline olefin resin to the surface layer (A), the film of the base layer (B) is formed. It can also improve sex. If the blending amount of the crystalline polyolefin resin is less than 3% by weight, the effect of improving the film-forming property is poor, and if it is 50% by weight or more, the uniform expandability and restorability of the base layer (B) may be lowered.
The crystalline olefin resin is not particularly limited, but for example, linear low-density polyethylene ( ^{preferably exceeding 910 kg / m 3} ), high-density polyethylene, high-pressure low-density polyethylene (density 910 kg / m). ⁽ Preferably more than 3), propylene-based homopolymers, propylene-based block copolymers, and the like can be exemplified. In particular, high-pressure low-density polyethylene having a density of more than 910 kg / m ³ is excellent in the effect of improving film-forming property with a small amount of addition.

It should be noted that various additives such as lubricants, antiblocking agents, antistatic agents, antifogging agents, and antioxidants are effective on the surface layer (A) as long as they do not interfere with the object of the present invention. It can be appropriately used for the purpose of providing an action. However, as described above, it may be desirable not to use a lubricant or an antiblocking agent depending on the application.

[Elastic film]
The elastic film of the present invention has a structure consisting of only the surface layer (A) and the base layer (B) as long as it includes at least the surface layer (A) and the base layer (B) (surface layer (A) / base layer (B)). It may be a configuration including another resin layer (C) (for example, surface layer (A) / resin layer (C) / base layer (B), surface layer (A) / base layer (B) / resin layer (C)). Etc.).
However, a configuration (surface layer (A) / base layer (B) / surface layer (A)) having a base material layer (B) between the two surface layers (A) is particularly preferable. When the surface layer (A) is provided on both sides of the base layer (B), the roll peelability is ensured regardless of which surface of the film the roll comes into contact with. Moreover, even if the film is stretched, there is no risk of curling. Even if the elastic film having a layer structure of the surface layer (A) / base layer (B) / other layer (C) is not curled after film formation, it is stretched once and then curled when the tension is removed. There is. When the layer structure is the surface layer (A) / base layer (B) / surface layer (A), the two surface layers (A) may have the same resin composition, but if the main components of the resin are the same. , Sub-ingredients, types of various additives, blending amounts, etc. may be different.

The thickness ratio of each layer of the elastic film is not particularly limited, but the thickness of the polyolefin-based film having excellent uniform expandability and resilience is t, the thickness of the surface layer (A) is tA, and the base layer (the base layer). When the thickness of B) is tB, it is desirable that 6 μm ≦ tA and 0.50 t ≦ tB. If the thickness tB of the base layer (B) is less than 1/2 of the total thickness t, the uniform expandability and resilience of the entire elastic film are reduced, and the film is stretched by 40% (1.4 of the original length). It becomes difficult to make the restoration rate after (stretching to double) 90% or more. Further, if the thickness of the surface layer (A) is less than 6 μm, it becomes difficult to form a stable film.

The thickness of the elastic film is not particularly limited and may be appropriately determined according to the intended use. When the film is used as a base film for a film for a semiconductor manufacturing process, it is usually 50 to 300 μm, particularly preferably 60 to 250 μm, and particularly preferably 70 to 200 μm. If the film is too thin, it will break easily, and if it exceeds 300 μm, it will only over-engineer.

When the elastic film is used as a base film for a film for a semiconductor manufacturing process, at least one surface layer (A) of the elastic film contains a conductive material such as a surfactant and a permanent antistatic polymer. Is preferable. When at least one surface layer (A) contains a conductive material, it is possible to accurately suppress or prevent the generation of static electricity on the semiconductor wafer. Examples of the surfactant include anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. Examples of the permanent antistatic polymer include polyester amide series, polyester amide, polyether ester amide, polyurethane series and the like. Further, as a typical permanent antistatic polymer, the trade name "Perestat (registered trademark)" manufactured by Sanyo Chemical Industries, Ltd. is exemplified.

The method for producing the elastic film of the present invention is not particularly limited, but for example, the resin composition for forming the surface layer (A) and the resin composition for molding the base layer (B) are separately extruded. Inflection co-extrusion method or T-die co-extrusion method that supplies to the machine and extrudes from one die, a method that extrudes and laminates the base layer (B) on the surface layer (A) that has been formed in advance, and two pre-filmed A method of extruding and laminating the base layer (B) between the surface layers (A) can be used. However, the T-die coextrusion method is suitable in consideration of the uniform expandability of the film and the production efficiency. In the inflation coextrusion method, the resin is easily oriented, so that the uniform expandability may decrease. Further, in the extrusion laminating method, one layer needs to be formed into a film in advance, so that the production efficiency is poor.
In order to improve the uniform expandability and resilience of the film, r- has a relatively high comonomer content (6% by weight or more, preferably about 6 to 11% by weight) as the resin forming the surface layer (A). In addition to adopting PP (α), it is desirable to adopt a T-die coextrusion-nip roll molding method using a nip roll having fine irregularities on the surface as a method for producing an elastic film. When the resin is extruded from a linear die (T die) and sandwiched between a cooling roll and a nip roll having fine irregularities (nip roll molding), even if a resin having a relatively high comonomer content is used for the surface layer (A). , The film-forming property (peeling property from the roll) can be supplemented by the unevenness formed on the film surface.

In order to obtain a dicing film, which is a kind of film for a semiconductor manufacturing process, from the elastic film of the present invention, it is necessary to apply an adhesive to one surface of the film. Therefore, prior to the application of the pressure-sensitive adhesive, it is preferable to apply a surface treatment such as a corona treatment to the surface layer to which the pressure-sensitive adhesive is applied. The surface-treated surface has improved adhesion to the adhesive. The pressure-sensitive adhesive may be applied by applying a pressure-sensitive adhesive diluted with a solvent such as methyl ethyl ketone, acetone, toluene, or dimethyl formaldehyde by a method such as die coating, curtain die coating, gravure coating, comma coating, bar coating, or lip coating. .. A separator is attached to the adhesive surface of the dicing film, if necessary.

The effects of the present invention will be described based on examples. The effect of the present invention was evaluated by the following method.

[Film formation]
The resin compositions shown in Tables 2 and 3 are formed into a film by a T-die (co) extrusion method. Those that were able to form a film without any particular problem are marked with ◯, those that had a problem with release from the roll and needed to adjust the transport tension are marked with Δ, and those that could not be formed with a film are marked with ×.

[Yield point elongation]
From the films of each example and comparative example, a No. 4 test piece (measurement portion width 10 mm) was prepared so that the flow direction of the film was the measurement direction, and the tensile speed was determined in accordance with JIS K7127 (1989). Perform a 100% tensile test at 50 mm / min (from 40 mm to 80 mm between chucks). When the distance between the chucks is changed from 40 mm to 80 mm, the case where the yield point is not found is marked with ◯, and the case where the yield point is seen is marked with x. If the yield point is seen, necking occurs when the film is stretched by 40% or more at the same time (so that each of the length and width is 1.4 times or more of the original length), and it can be expanded uniformly. It seems that even if the tension is removed after expansion, the film is already distorted and cannot be restored to its original shape.

[necking]
Cut out a film piece of 150 mm in length × 10 mm in width so that the direction you want to measure is the vertical direction, insert two lines in the center part in the vertical direction so that the distance is 50 mm, and between the two lines Make a test piece by marking four points so that the distance is 10 mm. This test piece is set in a tensile tester set to a chuck-to-chuck distance of 70 mm. At this time, set so that the center lines of the two lines inserted in the film and the center between the chucks coincide with each other. Next, it is stretched by 40% (until the distance between chucks becomes 98 mm) at a tensile speed of 200 mm / min, and the distance N between scores is measured in the stretched state. The distance N between the five grades, which is divided by two lines and four points, was 14 mm ± 1 mm in both the flow direction and width direction of the film. Let x be the thing.

[Restoration rate]
A film piece having a length of 150 mm and a width of 10 mm is cut out so that the direction to be measured is the vertical direction, and two lines are inserted in the central portion in the vertical direction so that the distance between the scores is 50 mm to prepare a test piece. Next, the test piece is set in a tensile tester in which the distance between chucks is set to 70 mm. At this time, set so that the center lines of the two lines inserted in the film and the center between the chucks coincide with each other. Next, at a tensile speed of 200 mm / min, the test piece is stretched by 50% (until the distance between chucks reaches 105 mm) or 100% (until the distance between chucks reaches 140 mm), held in that state for 300 seconds, and then held. Open the chuck and take out the test piece. When the shape of the test piece is stable, the distance L between the scores is measured, and the restoration rate is calculated by the formula (1).
Restoration rate (R) = (50 / L) x 100 ... Equation (1)

The following resins were used in each of the examples and comparative examples.

PE1: High pressure method low density polyethylene (density ^{919kg / m 3} MFR7g / 10min)
PE2: Ethylene-α-olefin copolymer (density 885 kg / m ³ MFR 3.6 g / 10 min)
PE3: Ethylene-α-olefin copolymer (density 915 kg / m3 MFR3.5 g / 10min)
(Density and MFR conform to JIS K 6922-1 MFR is 190 ℃ / 2.16kg)
SE1: Styrene-based elastomer (density ^{890kg / m 3} MFR3.5g / 10min)
SE2: Styrene-based elastomer (density ^{919kg / m 3} MFR7g / 10min)
(Density and MFR conform to JIS K 6922-1 MFR is 230 ℃ / 2.16kg)

[Example 1]
A resin composition (r-PP2: PE1 = 70% by weight: 30% by weight) composed of r-PP2 and PE1 was used as the resin for the surface layer (A), and r-PP1 (ethylene content) was used as the resin for the base layer (B). Using a 16% density 862 kg / m ³ , melting point 103.4 ° C.), a three-layer elastic film of surface layer (A) / base layer (B) / surface layer (A) was formed by a T-die coextrusion method. .. The film thickness was 80 μm, and the thickness ratio of each layer was 1: 4: 1.
The film formation could be performed stably. The resulting film was stretched 100% (up to twice its original length), but no yield point was observed. In addition, the restoration rate after stretching by 50% (up to 1.5 times the original length) and the restoration rate after stretching by 100% (up to twice the original length) were measured. The results are shown in Table 2. Since the restoration rate of the film of Example 1 after stretching by 50% exceeds 90%, the restoration rate after stretching by 40% also exceeds 90%.

[Examples 2 and 3, Reference Examples 1 and 2 ]
Examples 2 and 3 are the same as in Example 1 except that the resin composition of the surface layer (A) and the thickness ratio of the surface layer (A) / base layer (B) / surface layer (A) are changed as shown in Table 2. , The elastic films of Reference Examples 1 and 2 were obtained.
The film of Example 2 was able to be stably formed, had no yield point, no necking, and had a good restoration rate.
Since the surface of the film of Example 3 was composed of r-PP3 having a low ethylene content, the film-forming property was good, but a yield point was observed until the film was stretched 100%, and the film was further stretched by 40%. Occasionally necking was seen, and the recovery rate after 100% stretching was less than 90%.
In the films of Reference Examples 1 and 2 , the surface layer (A) was made of an ethylene-based copolymer having a low density, and the restoration rate was good, but some problems were observed in the release property from the roll.

[Comparative Examples 1 to 5]
Except for changing the resin composition of the surface layer (A), the base layer (B), the other layer (C), and the thickness ratio of the surface layer (A) / base layer (B) / other layer (C) as shown in Table 3. , The elastic films of Comparative Examples 1 to 5 were obtained in the same manner as in Example 1.
However, the film of Comparative Example 1 having no surface layer (A) did not peel off from the roll and could not be formed. Further, in the films of Comparative Examples 2 to 5, a yield point was observed until the film was stretched 100%, and necking was observed when the film was stretched 40%. Therefore, the films expanded 1.4 times (or more) than the original length. It seems that it cannot be used for such purposes. Moreover, the restoration rate at 100% elongation was much lower than that of the elastic film of the present invention.

[Uniform expandability test]
A square (1 cm square) is put in the elastic film of Example 1 and stretched 100% (twice the original length) at the same time in the vertical and horizontal directions at a speed of 10 mm / s with a table biaxial stretching machine. .. The squares that were 1 cm square before stretching became 2 cm square without distortion in the stretched state. It was confirmed that the elastic film of the present invention has excellent uniform expandability.

The elastic film of the present invention can be used as a film for a semiconductor manufacturing process such as a dicing film and an expanded film. In addition, since it exhibits excellent uniform expandability and resilience, it can be used for stretch films, poultice base materials, side tapes for disposable diapers, medical supporters, sports supporters, and the like.

Claims (5)

Table layer a polyolefin film sequentially provided three layers of (A) and the base layer (B) and the surface layer (A),
When the thickness of the surface layer (A) is tA, the thickness of the base layer (B) is tB, and the thickness of the polyolefin-based film is t, 6 μm ≦ tA and 0.50 t ≦ tB. ,
The base layer (B) is a random copolymer of propylene and ethylene, and the content of ethylene as a comonomer in the copolymer is 10% by weight or more and less than 30% by weight, in accordance with ASTM D1505. Contains 85% by weight or more of a propylene-based random copolymer (β) having a measured density of less than 875 kg / m ^3.
The surface layer (A) is composed of a propylene-based random copolymer (α) of 50% by weight or more and 100% by weight or less and a crystalline olefin-based resin of 0% by weight or more and less than 50% by weight .
The propylene-based random copolymer (α) has a lower content of ethylene as a comonomer in the copolymer than the propylene-based random copolymer (β), has a higher density, and is the copolymer (α). The content of ethylene as a copolymer in the above is 4 to 15% by weight.
The crystalline olefin resin is a polyolefin-based film having excellent uniform expandability and resilience, which is any one of linear low-density polyethylene, high-density polyethylene, and high-pressure low-density polyethylene. A polyolefin film according to claim 1 Symbol mounting, characterized the recovery ratio Rmd the film flow direction is determined by the following recovery ratio measuring method, the film width direction of the recovery ratio Rtd is both 90% A polyolefin film with excellent uniform expandability and resilience.
[Recovery rate measurement method]
A film piece having a length of 150 mm and a width of 10 mm is cut out so that the direction to be measured is the vertical direction, and two lines are inserted in the central portion in the vertical direction so that the distance between the scores is 50 mm to prepare a test piece. This test piece is set in a tensile tester set to a chuck-to-chuck distance of 70 mm so that the center lines of the two lines are at the center between the chucks, and 40% (chuck-to-chuck distance) at a tensile speed of 200 mm / min. The film is stretched (until it reaches 98 mm), held in that state for 300 seconds, and then the chuck is opened and the test piece is taken out. When the shape of the test piece is stable, the distance L between the scores is measured, and the restoration rate is calculated by the formula (1).
Restoration rate (R) = (50 / L) x 100 ... Equation (1) The polyolefin-based film according to claim 1 or 2, wherein the five scoring distances Nmd in the film flow direction and the five scoring distances Ntd in the film width direction measured by the following necking measurement method are all 14 mm ± 1 mm. A polyolefin-based film having excellent uniform expandability and resilience, which is characterized by being within.
[Necking measurement method]
Cut out a film piece of 150 mm in length × 10 mm in width so that the direction you want to measure is the vertical direction, insert two lines in the center part in the vertical direction so that the distance is 50 mm, and between the two lines Make a test piece by marking four points so that the distance is 10 mm. This test piece is set in a tensile tester set to a chuck-to-chuck distance of 70 mm so that the center lines of the two lines are at the center between the chucks, and 40% (chuck-to-chuck distance) at a tensile speed of 200 mm / min. The film is stretched (until 98 mm), and with the film stretched, the distance N between the five scores formed by the two lines and the four points is measured. A film for a semiconductor manufacturing process, wherein the polyolefin-based film having excellent uniform expandability and resilience according to any one of claims 1 to 3 is used as a base film. The film for a semiconductor manufacturing process according to claim 4 , wherein at least one surface layer (A) of the base film contains an antistatic agent.