JP7624307B2 - Multilayer films, adhesive films, and adhesive films for semiconductor manufacturing processes - Google Patents

Description

The present invention relates to adhesive films (tapes) used in the semiconductor manufacturing process, adhesive films (tapes) such as stickers, labels and marking films attached to signs, automobiles, etc. to add design features, multilayer films suitable for use as substrates for decorative sheets, etc., and adhesive films in which an adhesive layer is provided on the multilayer films.

Conventionally, polyvinyl chloride resin films (hereinafter also referred to as "PVC-based films"), which have excellent colorability, processability, scratch resistance, weather resistance, etc., have been widely used as the substrate for adhesive films (tapes), decorative sheets, etc., such as stickers, labels, and marking films that are affixed to signs, automobiles, etc. to add a design element.

The PVC film itself has rigidity, but a plasticizer is added to impart flexibility so that the film can function as an adhesive film. However, depending on the plasticizer used, the film may have poor compatibility with the adhesive, resulting in poor stability when used as an adhesive film, and the plasticizer may bleed out significantly. In addition, there is a tendency for restrictions on the use of plasticizers to be strengthened.
Therefore, polyolefin resin films have come to be widely used as an alternative material to PVC films.

Furthermore, in the process of manufacturing semiconductors, adhesive films for semiconductor wafer processing are used when cutting semiconductor wafers, packages, etc., and due to the above-mentioned problems, the use of polyolefin-based resin films is increasingly being used.
As such films for use in semiconductor manufacturing processes, films using PVC-based or polyolefin-based resins have been developed (for example, Patent Document 1). Also, Patent Document 2 discloses a substrate film for use in semiconductor manufacturing processes that is provided with antistatic properties and has excellent flexibility and heat resistance.

Furthermore, in recent years, semiconductor elements have become smaller and thinner, and there is a tendency for the expandability of the film to be more important in the expanding process for increasing the distance between chips on a semiconductor wafer. As chips become smaller, chips and devices are more likely to be damaged due to contact with each other, which has a greater impact on economics, such as a decrease in yield due to this.

To solve these problems, Patent Documents 3 and 4 disclose a dicing substrate film that contains a large amount of styrene-based elastomer and has excellent expandability.

Japanese Patent Application Publication No. 9-8111 JP 2020-84143 A Patent No. 4259050 JP 2018-125521 A

However, the inventions described in Patent Documents 1 and 2 are mainly composed of polyolefin resins or olefin elastomers, which have insufficient expandability, and therefore lack expandability.
In addition, although the invention described in Patent Document 3 makes extensive use of styrene-based elastomers, the document does not select materials taking into consideration the processability and handling properties of the film, and does not provide any detailed description of the styrene-based elastomers.
The invention described in Patent Document 4 describes an intermediate layer made of a styrene-based elastomer, and also describes that the expandability is excellent. However, when considering the film formability when molding the resin into a film, there is room for improvement in the selection of the styrene-based elastomer.

In view of these problems, the present invention aims to provide a film that has excellent film-forming properties when molding a resin into a film, and also has excellent expandability of the resulting film. Another aim of the present invention is to provide an adhesive film for use in the semiconductor manufacturing process that has excellent expandability and can ensure sufficient spacing between chips.

The inventors of the present invention have completed the present invention as a result of extensive research into a film that has excellent film-forming properties when molding a resin into a film and also has excellent expandability when the film is obtained.

That is, the gist of the present invention is as follows.
[1]
A multi-layer film having at least two or more layers,
At least one layer is an elastomer layer containing a polyolefin-based resin and a styrene-based elastomer,
The styrene-based elastomer has a styrene component content of 20% by mass or more and 60% by mass or less,
When the total amount of the resin constituting the elastomer layer is taken as 100% by mass, the content of the styrene-based elastomer is 60% by mass or more, and the thickness ratio of the elastomer layer to the total thickness of the multilayer film is 70% or more.
Multi-layer film.
[2]
The multilayer film according to [1], having a total thickness of 150 μm or less.
[3]
The multilayer film according to [1] or [2], wherein the polyolefin resin is a polypropylene resin and/or a polyethylene resin.
[4]
The multilayer film according to any one of [1] to [3], wherein the elastomer layer is used as a layer located in the middle of the film.
[5]
An adhesive film comprising an adhesive layer provided on at least one surface of the multilayer film according to any one of [1] to [4].
[6]
The adhesive film for semiconductor manufacturing process according to [5], which is used in a semiconductor manufacturing process.

The present invention makes it possible to provide a film that has excellent film-forming properties when molding a resin into a film, and also has excellent expandability of the resulting film. The present invention also makes it possible to provide an adhesive film for the semiconductor manufacturing process that has excellent expandability and can ensure sufficient spacing between chips.

The present invention is described in detail below, but is not limited to the following embodiments and can be modified and implemented in various ways within the scope of the gist. In this specification, when the expression "~" is used, it is used as an expression including the numerical values or physical property values before and after it.

One embodiment of the present invention is a multilayer film that contains a polyolefin resin and a styrene elastomer with a styrene component content in the range of 20 to 60% by mass, has at least one elastomer layer with a styrene elastomer content of 60% by mass or more when the total amount of the resins constituting the film is taken as 100% by mass, and the thickness of the layer accounts for 70% or more of the total thickness of the multilayer film.

<Polyolefin resin>
The elastomer layer of the multilayer film used in the present invention contains a polyolefin resin as an essential component.
Polyolefin resins are preferably used from the viewpoints of availability, the comparative ease with which heat resistance and flexibility can be adjusted, and compatibility with the styrene elastomer described below.
As the polyolefin-based resin, one or more resins selected from polypropylene-based resins, polyethylene-based resins, and olefin-based elastomers are preferably used from the viewpoints of availability, flexibility, ease of handling, economic efficiency, etc. Among them, polypropylene-based resins and polyethylene-based resins are preferred from the viewpoints of availability and economic efficiency, and because it is relatively easy to adjust the heat resistance and flexibility.

Examples of polypropylene-based resins include homopolymers of propylene (homopolypropylene), copolymers containing propylene as the main component and other monomers copolymerizable with propylene, and mixtures of these.
Examples of the copolymers containing propylene as a main component and other monomers copolymerizable with propylene include random copolymers (random polypropylenes) and block copolymers (block polypropylenes) of propylene and ethylene or other α-olefins, and block or graft copolymers containing a rubber component.
The α-olefin used as the other monomer copolymerizable with propylene is preferably one having 4 to 12 carbon atoms, and examples thereof include 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene, and 1-decene. One or a mixture of two or more of these is used.

Examples of polyethylene-based resins include ethylene homopolymers, copolymers of ethylene mainly composed of ethylene and other monomers copolymerizable therewith (low-density polyethylene (LDPE), high-pressure low-density polyethylene, linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), ethylene-based copolymers obtained by polymerization using a metallocene catalyst (metallocene-based polyethylene), ethylene-vinyl acetate copolymers, ethylene-methyl (meth)acrylate copolymers, ethylene-ethyl (meth)acrylate copolymers, ethylene-butyl (meth)acrylate copolymers, ethylene-(meth)acrylic acid copolymers, and metal ion crosslinked resins (ionomers) of ethylene-(meth)acrylic acid copolymers.
Among these, from the viewpoints of ease of availability, ease of handling of the resin, and ease of adjusting the flexibility of the resulting film, it is preferable to use high density polyethylene (HDPE), low density polyethylene (LDPE), and linear low density polyethylene (LLDPE).

The olefin-based elastomer is a soft resin containing a polyolefin-based resin and a rubber component, and may be one in which the rubber component is dispersed in the polyolefin-based resin, or one in which the two are copolymerized with each other.
Specific examples of the olefin-based elastomer include amorphous elastic copolymers mainly composed of olefins, such as ethylene-propylene copolymer elastomers, ethylene-1-butene copolymer elastomers, ethylene-propylene-1-butene copolymer elastomers, ethylene-1-hexene copolymer elastomers, ethylene-1-octene copolymer elastomers, ethylene-styrene copolymer elastomers, ethylene-norbornene copolymer elastomers, propylene-1-butene copolymer elastomers, ethylene-propylene-non-conjugated diene copolymer elastomers, ethylene-1-butene-non-conjugated diene copolymer elastomers, and ethylene-propylene-1-butene-non-conjugated diene copolymer elastomers, as well as derivatives and acid-modified derivatives thereof.

The melt flow rates of the polypropylene resins, polyethylene resins, olefin elastomers, etc. mentioned above are appropriately selected depending on the molding method and application, but it is preferable that the value measured under a temperature condition of 190°C or 230°C and a load of 2.16 kg is 0.1 to 50 g/10 min. If it is 0.1 g/10 min or more, the moldability of the film is good, and if it is 50 g/10 min or less, it is possible to maintain good thickness precision of the film. It is more preferable that it is 0.5 to 40 g/10 min., and even more preferable that it is 1.0 to 30 g/10 min.

Regarding the strength of polypropylene-based resins, polyethylene-based resins, olefin-based elastomers, etc., the tensile modulus of a film obtained from these resins alone is preferably within the range of 50 to 2000 MPa. If the tensile modulus is within the range of 50 to 2000 MPa, it is possible to impart appropriate flexibility to the film of the present invention. It is more preferably within the range of 80 to 1900 MPa, and even more preferably within the range of 100 to 1800 MPa.
The polyolefin resin may be used alone or in combination of two or more kinds. The resin may be appropriately selected as needed, taking into consideration the flexibility, heat resistance, and film formability of the resulting multilayer film.

<Styrene-based elastomer>
The elastomer layer of the multilayer film used in the present invention contains a styrene-based elastomer as an essential component in addition to the above-mentioned polyolefin-based resin.
Furthermore, when the total amount of resin constituting the elastomer layer is taken as 100% by mass, the content of the styrene-based elastomer is 60% by mass or more, which makes it possible to impart to the multilayer film of the present invention expandability that is difficult to achieve in films whose main component is polyolefin-based resin, and therefore a styrene-based elastomer is necessary.

The styrene-based elastomer is preferably a block copolymer represented by the following formula (I) or (II).
X-(Y-X)n...(I)
(X-Y)n...(II)
In general formulas (I) and (II), X is an aromatic vinyl polymer block (hereinafter referred to as a styrene component) typified by styrene, and in formula (I), the degree of polymerization at both ends of the molecular chain may be the same or different. Y is at least one selected from a butadiene polymer block, an isoprene polymer block, a butadiene/isoprene copolymer block, a hydrogenated butadiene polymer block, a hydrogenated isoprene polymer block, a hydrogenated butadiene/isoprene copolymer block, a partially hydrogenated butadiene polymer block, a partially hydrogenated isoprene polymer block, and a partially hydrogenated butadiene/isoprene copolymer block. n is an integer of 1 or more.

Specific examples include styrene-ethylene-butylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, styrene-ethylene-ethylene-propylene-styrene copolymer, styrene-butadiene-butene-styrene copolymer, styrene-butadiene-styrene copolymer, styrene-isoprene-styrene copolymer, styrene-hydrogenated butadiene diblock copolymer, styrene-hydrogenated isoprene diblock copolymer, styrene-butadiene diblock copolymer, styrene-isoprene diblock copolymer, etc., among which styrene-ethylene-butylene-styrene copolymer, styrene-ethylene-propylene-styrene copolymer, styrene-ethylene-ethylene-propylene-styrene copolymer, and styrene-butadiene-butene-styrene copolymer are preferred. Also usable are block copolymers that are styrene-ethylene-butylene-crystalline olefin copolymers.

In the present invention, the content of the styrene component in the styrene-based elastomer must be within the range of 20% by mass or more and 60% by mass or less. If the content of the styrene component is 20% by mass or more, the resulting film will not be too flexible and will be excellent in handleability, and if the content is 60% by mass or less, compatibility with the polyolefin-based resin will not be significantly impaired, making it possible to suppress a significant decrease in physical properties due to a decrease in compatibility. It is preferably within the range of 22 to 55% by mass, more preferably 25 to 50% by mass.
The content of the styrene component and the contents of other components can be measured by ¹ H-NMR or ¹³ C-NMR. Here, the "content of the styrene component" refers to the content (mass%) of an aromatic vinyl polymer block represented by styrene based on the mass of the styrene-based elastomer.

The melt flow rate of the styrene elastomer (measured at a temperature of 230°C under a load of 2.16 kg) is preferably 0.1 to 10 g/10 min, more preferably 0.15 to 9 g/10 min, and particularly preferably 0.2 to 8 g/10 min. If the melt flow rate of the styrene elastomer is less than 0.1 g/10 min or exceeds 10 g/10 min, compatibility with the polyolefin resin decreases and film formability deteriorates, so sufficient flexibility and expandability may not be achieved.

Commercially available styrene-based elastomers include, for example, Tufprene A, Tufprene 125, Asaprene T-438, Asaprene T-439, Tuftec H1221, Tuftec H1041, Tuftec H1052, Tuftec H1053, Tuftec H1517 (all manufactured by Asahi Kasei Corporation), Septon 4099, Septon HG252, Septon 8004, Septon 8006, Examples include Septon 8007L, Septon HG252, Septon V9461, Septon V9475, Hybler 7311, Hybler 7125F, Hybler 5127, Hybler 5125 (all manufactured by Kuraray Co., Ltd.), Dynaron 1320P, Dynaron 4600P, Dynaron 8300P, Dynaron 8903P, Dynaron 9901P (all manufactured by JSR Co., Ltd.), etc.

Commercially available styrene-based elastomers with a styrene content in the range of 20% by mass to 60% by mass include, for example, Tuftec H1041, Tuftec H1052, Tuftec H1053, and Tuftec H1517 (all manufactured by Asahi Kasei Corporation), Septon 8007L, Septon HG252, and Hybra 5125 (all manufactured by Kuraray Co., Ltd.), Dynaron 4600P, Dynaron 8903P, and Dynaron 9901P (all manufactured by JSR Corporation).

The above styrene-based elastomers may be used alone or in combination of two or more types. They can be appropriately selected as needed, taking into consideration the film-forming properties when obtaining a multilayer film, and the flexibility, handling properties, and expandability of the obtained multilayer film. From the viewpoint of the film-forming properties of the multilayer film and the performance of the obtained film, it is more preferable to use two or more types in combination.

<Other resins>
The elastomer layer of the laminated film of the present invention may contain resins other than the polypropylene resin, polyethylene resin, olefin elastomer, and styrene elastomer described above, such as cyclic olefin resins and polymethylpentene resins.

Examples of cyclic olefin resins include norbornene polymers, vinyl alicyclic hydrocarbon polymers, and cyclic conjugated diene polymers. Of these, norbornene polymers are preferred. Norbornene polymers include ring-opening polymers of norbornene monomers and norbornene copolymers obtained by copolymerizing norbornene monomers with α-olefins such as ethylene. Hydrogenated products of these can also be used.

<Other ingredients>
In order to impart the required performance to the resulting film, various additives may be blended in the multilayer film of the present invention (i.e., the elastomer layer and layers other than the elastomer layer) as components other than the polyolefin-based resin and styrene-based elastomer to impart heat resistance, weather resistance, antistatic performance, etc.
Specific examples of the additives that may be used include antistatic agents, antioxidants, neutralizing agents, lubricants, antiblocking agents, plasticizers, heat stabilizers, light stabilizers, dyes and pigments, crystal nucleating agents, ultraviolet absorbers, fillers, inorganic fillers that impart rigidity, and elastomers other than those mentioned above that impart flexibility, within the scope of not impairing the effects of the present invention.
When it is necessary to impart different properties to each layer of a multi-layer film, various additives can be added to each layer.

Any known antistatic agent can be used, but it is preferable to use a polymeric antistatic agent from the viewpoints of compatibility with the resulting multilayer film, imparting long-term antistatic performance, and suppressing bleeding out of the antistatic agent over time.

The polymeric antistatic agent may be a known one, for example a block copolymer of a hydrophobic block and a hydrophilic block. In the polymeric antistatic agent, the hydrophobic block and the hydrophilic block form a block copolymer through ester bonds, ether bonds, amide bonds, imide bonds, urethane bonds, urea bonds, etc.

Examples of hydrophobic blocks include polyolefin blocks, and examples of polyolefin blocks include blocks made of polyethylene, polypropylene, and ethylene-propylene copolymers.

A hydrophobic block such as a polyolefin block has polar groups such as carbonyl groups, hydroxyl groups, and amino groups at both ends. A block copolymer of a hydrophobic block and a hydrophilic block can be obtained by polymerizing the polar groups at both ends of the hydrophobic block with the carbonyl groups, hydroxyl groups, and amino groups present at both ends of the hydrophilic block, or by crosslinking the polar groups with diisocyanate, diglycidyl ether, or the like.

Hydrophilic blocks can include, for example, polyether blocks, polyether-containing hydrophilic polymer blocks, cationic polymer blocks, and anionic polymer blocks.
In addition, the polymer-type antistatic agent may contain an alkali metal or alkaline earth metal salt, a quaternary ammonium salt, a surfactant, an ionic liquid, etc., in order to further improve the antistatic properties, within the range that does not impair the effects of the present invention.

Commercially available polyether-polyolefin block copolymers, which are polymer-type antistatic agents, include, for example, Pellestat 300, Pellestat 230, Pelletron UC, Pelletron PVL, and Pelletron PVH (all manufactured by Sanyo Chemical Industries, Ltd.).

As the ultraviolet absorbing agent, a known agent can be used, for example, a benzotriazole-based ultraviolet absorbing agent, a benzophenone-based ultraviolet absorbing agent, a triazine-based ultraviolet absorbing agent, etc.

Any known light stabilizer can be used, such as a hindered amine light stabilizer.

As lubricants and antiblocking agents, known agents such as organic particles, inorganic particles, and amide compounds can be used. In addition, it is preferable to use silicone-olefin copolymers, as they have excellent compatibility with the polyolefin resins described above, prevent defects caused by bleed-out on the surface of the resulting film, and can provide long-term scratch resistance and slipperiness.

<Multi-layer film>
The multilayer film of the present invention is a multilayer film having at least two or more layers, containing the above-mentioned polyolefin-based resin and styrene-based elastomer, having at least one elastomer layer in which the styrene-based elastomer content is 60% by mass or more, and the proportion of the thickness of the elastomer layer in the total thickness of the multilayer film is 70% or more.

The multilayer film of the present invention has at least two or more layers, all of which may be elastomer layers, or some of which may be elastomer layers.
When the multilayer film has two or more elastomer layers, the total of these layers should account for 70% or more of the total thickness of the multilayer film, thereby making it possible to impart sufficient expandability.
When the elastomer layer is two or more layers, the resin composition of each elastomer layer may be the same or different.

The elastomer layer may be in either the front or back layer of the multilayer film, or in an intermediate layer. However, if a styrene-based elastomer is placed in the front or back layer, tackiness due to the styrene-based elastomer may occur on the film surface, which may cause problems such as the film sticking to the roll when forming the film, problems with transportation, and significant blocking of films when the film is wound up. Therefore, it is preferable that the elastomer layer is used in an intermediate layer of the multilayer film.
Here, the layer located in the middle of the multilayer film means a so-called middle layer when the multilayer film is composed of, for example, three layers, but when the multilayer film is composed of four or more layers, it includes not only the middle layer but also the layers before and after it. For example, when the multilayer film is composed of four layers, the "layer located in the middle of the multilayer film" includes the second and third layers counting from the surface layer, and when the multilayer film is composed of five layers, in addition to the third layer counting from the surface layer, the second and fourth layers from the surface layer are also included in the "layer located in the middle of the multilayer film". Therefore, when the multilayer film is composed of four layers, all of the "layers located in the middle of the multilayer film" may be elastomer layers, and a part of the "layer located in the middle of the multilayer film" may be elastomer layers.

The layers other than the elastomer layer of the multilayer film of the present invention may be layers containing various polymers as main components, but are preferably layers containing a polyolefin resin as main component.
Specific examples of the multilayer film include a two-type two-layer structure with a layer mainly made of polyolefin resin as the surface layer and an elastomer layer as the back layer, a two-type three-layer structure with a layer mainly made of polyolefin resin as the surface layer and an elastomer layer as the middle layer, a three-type three-layer structure with a layer mainly made of polyolefin resin as the surface layer and an elastomer layer as the middle layer, and a three-type three-layer structure with a layer mainly made of polyolefin resin and an elastomer layer as the middle layer, in which different polyolefin resins are used on the front and back, and a multilayer film having a multilayer structure of more than two layers. From the viewpoint of ease of film formation and ease of handling of equipment, a two-type two-layer structure, a two-type three-layer structure, or a three-type three-layer structure is preferable.

In addition, when a layer other than the elastomer layer, such as the front and back layers of the multilayer film, is a layer mainly composed of a polyolefin resin, the content of the polyolefin resin in the resin composition used for the layer is preferably 50% by mass or more. By making the content of the polyolefin resin 50% by mass or more, the film formability when processed into a film can be improved, and it is also easy to adjust the flexibility and heat resistance of the resulting multilayer film. It is more preferably 55% by mass or more, and even more preferably 60% by mass or more. For layers other than the elastomer layer, such as the front and back layers of the multilayer film, the resins other than the polyolefin resin described in the above section on styrene-based elastomers and other resins can be used.

The total thickness of the multilayer film of the present invention is preferably 30 to 250 μm. If it is 30 μm or more, the film production properties and the handleability of the resulting film will be good, and if it is 250 μm or less, it will be possible to maintain good processability in terms of economy and adhesion processing using the film. Furthermore, from the viewpoints of economy and expandability, it is more preferable that it is in the range of 30 to 200 μm, and even more preferable that it is in the range of 30 to 150 μm.

The tensile modulus of the multilayer film of the present invention is preferably within the range of 50 to 1500 MPa. If it is 50 MPa or more, the film is given sufficient rigidity, making it possible to maintain good handleability, and if it is 1500 MPa or less, it is possible to maintain good processability of the film in the step of laminating an adhesive layer to the film, and furthermore, it is possible to make the load on the film and the device during expansion appropriate. It is more preferably within the range of 50 to 1000 MPa, and even more preferably within the range of 50 to 500 MPa.

The expandability of the multilayer film can be measured using a wafer expansion device manufactured by Hugle Electronics. In order to confirm the influence of the adhesive layer laminated on the multilayer film, it is preferable to use the adhesive film after laminating the adhesive layer. The adhesive film will be described later.
The expandability can be measured under the following conditions.

<Method of measuring expandability>
A line was drawn in the center of the adhesive film sample, and then further lines were drawn at 30 mm intervals in the MD and TD directions to form a 30 mm square grid. After expansion, the length of the grid was measured at three points in the MD direction and three points in the TD direction, and the expansion rate at each point was calculated using the following formula.

上記エキスパンド条件にて測定した際の拡張率が、１１０％以上であるものをエキスパンド性が良好であると判断することが可能である。１１０％以上の拡張率を示すことで、エキスパンド後のチップの間隔を十分なものとすることが可能となる。より好ましくは１１２％以上、さらに好ましくは１１４％以上である。 <Calculation formula>

It is possible to judge that the expandability is good when the expansion rate measured under the above expanding conditions is 110% or more. By showing an expansion rate of 110% or more, it is possible to make the tip spacing after expansion sufficient. It is more preferable that it is 112% or more, and even more preferable that it is 114% or more.

The ring size, thrust speed, thrust amount, and stage temperature for the expansion test can be set arbitrarily as long as the conditions are such that the wafer size, the film is prevented from tearing or ripping during expansion, and the chip spacing is sufficient.

As a method for forming the multilayer film of the present invention, a known method can be used, but it is preferable to use a melt extrusion molding method. Among melt extrusion molding methods, a T-die molding method in which a molten resin is extruded from an extruder having a T-die and cooled and solidified to obtain a film is more preferable.

In order to obtain a film, it is preferable to use a co-extrusion T-die molding method using a plurality of extruders. By using a co-extrusion T-die molding method using a plurality of extruders, it is possible to obtain a multi-layer film, and it is possible to have a layer made of the resin composition of the present invention on only one of the front and back surfaces, or on both the front and back surfaces.
Furthermore, by extruding the same resin from all the extruders, it is possible to obtain a substantially single-layer film in which all layers are made of the same resin composition.

T-die coextrusion molding methods include a method in which multiple resin layers are formed into a film using a multi-manifold die, then brought into contact in a T-die to form a multi-layered film, and a method in which multiple resins are joined together using a device called a feed block, which joins molten resins, and then bonded together to obtain a multi-layered film.

If necessary, one or both sides of the film may be subjected to a surface treatment such as plasma treatment, corona treatment, ozone treatment, or flame treatment. Depending on the intended use of the resulting film, it is possible to select whether to perform a surface treatment on one or both sides.

It is also preferable that the thickness of the elastomer layer accounts for 70% or more of the total thickness of the multilayer film. By making it 70% or more, it is possible to impart sufficient expandability to the resulting multilayer film. It is more preferable that the thickness of the elastomer layer accounts for 75% or more of the total thickness of the multilayer film, and even more preferable that it is 80% or more.

<Adhesive film>
The multilayer film of the present invention can be made into an adhesive film by laminating an adhesive layer on at least one surface of the multilayer film of the present invention (hereinafter also referred to as the "adhesive film of the present invention").

The adhesive used for the adhesive layer is not particularly limited, but various adhesives such as natural rubber resins, acrylic resins, styrene resins, silicone resins, and polyvinyl ether resins can be used. In addition, a functional layer such as an adhesive layer or a thermosetting resin layer may be provided on the adhesive layer.

In the pressure-sensitive adhesive film of the present invention, one or both sides of the film before laminating the pressure-sensitive adhesive layer may be subjected to the above-mentioned surface treatment. In addition, a primer layer may be provided between the base film and the pressure-sensitive adhesive layer, if necessary.
The thickness of the adhesive layer and the primer layer can be appropriately determined according to need.

The adhesive film of the present invention uses a film with excellent expandability, making it suitable for use in semiconductor manufacturing processes.

The present invention will be specifically explained below with examples and comparative examples, but the present invention is not limited to these examples. The materials used in the following examples and comparative examples, and the methods for measuring the evaluated properties, are as follows.

[Materials used]
<Polyolefin resin>
Homopolypropylene:
"FLX80H5" manufactured by Japan Polypropylene (homopolypropylene, melt flow rate at 230°C and 2.16 kg: 8.0 g/10 min, melting point: 163°C, tensile modulus of single film: 900 MPa)
Random Polypropylene:
SunAllomer Corporation, "PC630A" (random polypropylene, melt flow rate at 230°C and 2.16 kg: 7.5 g/10 min, melting point: 135°C, tensile modulus of single film: 600 MPa)
Olefin elastomer:
"Wellnex RFX4V" manufactured by Japan Polypropylene (olefin elastomer, melt flow rate at 230°C and 2.16 kg: 6.0 g/10 min, melting point: 127°C, tensile modulus of single film: 250 MPa)
Low density polyethylene:
"Novatec LC500" manufactured by Japan Polyethylene Corporation (low density polyethylene, melt flow rate at 190°C and 2.16 kg: 4.0 g/10 min, melting point: 106°C, tensile modulus of single film: 140 MPa)

<Styrene-based elastomer>
Styrene-based elastomer (A):
Asahi Kasei Corporation, "Tuftec H1221" (Melt flow rate at 230°C and 2.16 kg: 4.5 g/10 min, styrene content: 12% by mass, styrene-ethylene-butylene-styrene copolymer)
Styrene-based elastomer (B):
Asahi Kasei Corporation, "Tuftec H1041" (Melt flow rate at 230°C and 2.16 kg: 5.0 g/10 min, styrene content: 30% by mass, styrene-ethylene-butylene-styrene copolymer)
Styrene-based elastomer (C):
Asahi Kasei Corporation, "Tuftec H1517" (Melt flow rate at 230°C and 2.16 kg: 3.0 g/10 min, styrene content: 43% by mass, styrene-ethylene-butylene-styrene copolymer)
Styrene-based elastomer (D):
"Dynaron 4600P" manufactured by JSR Corporation (melt flow rate at 230°C and 2.16 kg: 5.5 g/10 min, styrene content: 20% by mass, styrene-ethylene-butylene-crystalline olefin copolymer)

<Preparation of Resin Composition>
The polyolefin resin and the styrene elastomer were mixed to a total of 100 parts by mass and mixed by dry blending. After visually confirming that the mixture was uniformly mixed, a resin composition for film molding was prepared for each of the surface layer, the intermediate layer, and the back layer.

<Film production method>
The dry-blended raw materials were fed into the hoppers of three Toshiba Machine single-screw extruders (surface layer: 35φmm, L/D=25mm, middle layer: 50φmm, L/D=32, back layer: 35φmm, L/D=25mm), the extruder temperature of each extruder was set to 190-240°C, and the three-layer structure of surface layer/middle layer/back layer was merged in the feed block section and extruded from a 650 mm wide T-die (temperature setting 240°C, lip opening 0.5 mm). The rotation speed of each extruder was set so that the thickness structure would be as shown in Table 1.

The extruded molten resin was cooled and solidified using a winding machine equipped with a mirror-like cooling roll (cooling roll 700 mm wide x φ350 mm, roll temperature approximately 30°C), after which corona treatment was performed on both sides and the film was wound up to obtain a multilayer film having a specified thickness and consisting of two types of three layers or three types of three layers.
In the present invention, the mirror-finished surface of the obtained film facing the cooling roll is referred to as the surface layer.

[Thickness of each layer]
The thickness of each layer was calculated from the amount of resin extruded from each extruder, and was set. Furthermore, the cross-sectional observation of the obtained film confirmed that the thickness was as set.

[Total film thickness]
The thickness of the film was measured at the center and both ends using a contact thickness meter to confirm that the film had the desired thickness.

[Film formability]
When a film was produced by the above-mentioned film-forming method, the stability of the film thickness and the ease of handling were evaluated according to the following criteria.
◯: Easy to handle and good thickness stability (within ±5%)
×: Too flexible and difficult to handle, expands and contracts during transportation, resulting in poor thickness accuracy (±5% or more)

[Expandability]
The adhesive film coated with an acrylic adhesive was expanded under the following conditions using a wafer expansion device "HS-1840" manufactured by Hugle Electronics, to check the expandability.
In addition, a line was drawn in the center of the adhesive film, and further lines were drawn at 30 mm intervals in the MD and TD directions to form a grid of 30 mm squares. After expansion, the length of the grid was measured at three points in the MD direction and three points in the TD direction, and the expansion rate at each point was calculated using the following formula, and the average value in the MD and TD directions was used as the value of expandability (%). Those that could be expanded by 110% or more under the following expansion conditions were judged to have good expandability.

<Expanding conditions>
Ring size: diameter 180mm
Push-up amount: 50mm
Push-up speed: 6.2 mm/sec
Stage temperature: 60°C
<Calculation formula>

[Example 1]
A film having a thickness of 80 μm and consisting of three kinds and three layers was obtained by the above-mentioned film-forming method using random polypropylene as the resin for the surface layer, random polypropylene, low-density polyethylene, styrene-based elastomer (B) and styrene-based elastomer (C) as the resin for the intermediate layer, and low-density polyethylene as the resin for the back layer in the amounts shown in Table 1. The thicknesses of the layers were 4 μm for the surface layer, 68 μm for the intermediate layer, and 8 μm for the back layer, and the ratio of each thickness was 5% for the surface layer, 85% for the intermediate layer, and 10% for the back layer.
The film had good formability and could be sampled without any significant change in thickness. The film was also not too flexible and was judged to have excellent handleability.
The tensile modulus of the obtained film was 270 MPa, and it was confirmed that the film had sufficient rigidity to be easy to handle. The tensile elongation at break was 670%, and no decrease in the elongation at break due to deterioration of the compatibility between the styrene-based elastomer and the polyolefin-based resin was confirmed.
Next, an acrylic adhesive was applied onto the separator by a comma coating method so that the adhesive layer would have a thickness of 25 μm after drying, and the adhesive layer was formed after drying for 5 minutes in a hot air dryer at 80° C. The adhesive layer side of the prepared separator was attached to the cooling roll side of the present film to obtain an adhesive film in which the film of the present invention and the adhesive layer were laminated.
The separator of the obtained adhesive film was peeled off and an expansion test was performed under the above-mentioned expansion conditions. The average value of three points in the MD direction was 123.3%, and the average value of three points in the TD direction was 123.3%, meaning that the film expanded by more than 110%, confirming that the film has good expandability and that it can provide sufficient chip spacing when used in semiconductor processing applications.

[Example 2]
The same procedure as in Example 1 was repeated except that the thickness of each layer was 4 μm for the surface layer, 60 μm for the middle layer, and 16 μm for the back layer, and the ratio of each thickness was 5% for the surface layer, 75% for the middle layer, and 20% for the back layer.
The film had good formability and could be sampled without any significant change in thickness. The film was also not too flexible and was judged to have excellent handleability.
The tensile modulus of the obtained film was 260 MPa, and it was confirmed that the film had sufficient rigidity to be easy to handle. The tensile elongation at break was 650%, and no decrease in the elongation at break due to deterioration of the compatibility between the styrene-based elastomer and the polyolefin-based resin was confirmed.
Next, an acrylic adhesive was applied onto the separator by a comma coating method so that the adhesive layer would have a thickness of 25 μm after drying, and the adhesive layer was formed after drying for 5 minutes in a hot air dryer at 80° C. The adhesive layer side of the prepared separator was attached to the cooling roll side of the present film to obtain an adhesive film in which the film of the present invention and the adhesive layer were laminated.
The separator of the obtained adhesive film was peeled off and an expansion test was performed under the above-mentioned expansion conditions. The average value of three points in the MD direction was 120.0%, and the average value of three points in the TD direction was 121.7%, indicating an expansion of more than 110%, confirming that the film has good expandability and that it can provide sufficient chip spacing when used in semiconductor processing applications.

[Example 3]
The same procedure as in Example 2 was carried out except that the styrene-based elastomer (C) and the styrene-based elastomer (D) were used as the styrene-based elastomer for the intermediate layer, and the contents of the various resins were as shown in Table 1.
The film had good formability and could be sampled without any significant change in thickness. The film was also not too flexible and was judged to have excellent handleability.
The tensile modulus of the obtained film was 260 MPa, and it was confirmed that the film had sufficient rigidity to be easy to handle. The tensile elongation at break was 640%, and no decrease in the elongation at break due to deterioration of the compatibility between the styrene-based elastomer and the polyolefin-based resin was confirmed.
Next, an acrylic adhesive was applied onto the separator by a comma coating method so that the adhesive layer would have a thickness of 25 μm after drying, and the adhesive layer was formed after drying for 5 minutes in a hot air dryer at 80° C. The adhesive layer side of the prepared separator was attached to the cooling roll side of the present film to obtain an adhesive film in which the film of the present invention and the adhesive layer were laminated.
The separator of the obtained adhesive film was peeled off and an expansion test was performed under the above-mentioned expansion conditions. The average value of three points in the MD direction was 112.8%, and the average value of three points in the TD direction was 114.4%, indicating an expansion of more than 110%, confirming that the film has good expandability and that it can provide sufficient chip spacing when used in semiconductor processing applications.

[Example 4]
The same procedure as in Example 3 was carried out except that the styrene-based elastomer (C) and the styrene-based elastomer (D) were used as the styrene-based elastomer for the intermediate layer, and the contents of the various resins were as shown in Table 1.
The film had good formability and could be sampled without any significant change in thickness. The film was also not too flexible and was judged to have excellent handleability.
The tensile modulus of the obtained film was 210 MPa, and it was confirmed that the film had sufficient rigidity to be easy to handle. The tensile elongation at break was 640%, and no decrease in the elongation at break due to deterioration of the compatibility between the styrene-based elastomer and the polyolefin-based resin was confirmed.
Next, an acrylic adhesive was applied onto the separator by a comma coating method so that the adhesive layer would have a thickness of 25 μm after drying, and the adhesive layer was formed after drying for 5 minutes in a hot air dryer at 80° C. The adhesive layer side of the prepared separator was attached to the cooling roll side of the present film to obtain an adhesive film in which the film of the present invention and the adhesive layer were laminated.
The separator of the obtained adhesive film was peeled off and an expansion test was performed under the above-mentioned expansion conditions. The average value of three points in the MD direction was 113.3%, and the average value of three points in the TD direction was 114.4%, indicating an expansion of more than 110%, confirming that the film has good expandability and that it can provide sufficient chip spacing when used in semiconductor processing applications.

[Example 5]
A 100 μm-thick film consisting of three types and three layers was obtained by the above-mentioned film-forming method using homopolypropylene as the resin for the surface layer, homopolypropylene, low-density polyethylene, styrene-based elastomer (B) and styrene-based elastomer (C) as the resin for the intermediate layer, and low-density polyethylene as the resin for the back layer in the amounts shown in Table 1. The thicknesses of the layers were 10 μm for the surface layer, 80 μm for the intermediate layer, and 10 μm for the back layer, and the ratio of each thickness was 10% for the surface layer, 80% for the intermediate layer, and 10% for the back layer.
The film had good formability and could be sampled without any significant change in thickness. The film was also not too flexible and was judged to have excellent handleability.
The tensile modulus of the obtained film was 310 MPa, and it was confirmed that the film had sufficient rigidity to be easy to handle. The tensile elongation at break was 630%, and no decrease in the elongation at break due to deterioration of the compatibility between the styrene-based elastomer and the polyolefin-based resin was confirmed.
Next, an acrylic adhesive was applied onto the separator by a comma coating method so that the adhesive layer would have a thickness of 25 μm after drying, and the adhesive layer was formed after drying for 5 minutes in a hot air dryer at 80° C. The adhesive layer side of the prepared separator was attached to the cooling roll side of the present film to obtain an adhesive film in which the film of the present invention and the adhesive layer were laminated.
The separator of the obtained adhesive film was peeled off and an expansion test was performed under the above-mentioned expansion conditions. The average value of three points in the MD direction was 115.6%, and the average value of three points in the TD direction was 114.4%, indicating an expansion of more than 110%, confirming that the film has good expandability and that it can provide sufficient chip spacing when used in semiconductor processing applications.

[Comparative Example 1]
A film having a thickness of 80 μm and consisting of two kinds and three layers was obtained by the above-mentioned film-forming method using homopolypropylene and olefin-based elastomer as the resin for the surface layer, homopolypropylene, olefin-based elastomer and styrene-based elastomer (B) as the resin for the intermediate layer, and homopolypropylene and olefin-based elastomer as the resin for the back layer in the amounts shown in Table 1. The thicknesses of the layers were 4 μm for the surface layer, 72 μm for the intermediate layer, and 4 μm for the back layer, and the ratio of each thickness was 5% for the surface layer, 90% for the intermediate layer, and 5% for the back layer.
The film had good formability and could be sampled without any significant change in thickness. The film was also not too flexible and was judged to have excellent handleability.
The tensile modulus of the obtained film was 330 MPa, and it was confirmed that the film had sufficient rigidity to be easy to handle. The tensile elongation at break was 740%, and no decrease in the elongation at break due to deterioration of the compatibility between the styrene-based elastomer and the polyolefin-based resin was confirmed.
Next, an acrylic adhesive was applied onto the separator by a comma coating method so that the adhesive layer would have a thickness of 25 μm after drying, and the adhesive layer was formed after drying for 5 minutes in a hot air dryer at 80° C. The adhesive layer side of the prepared separator was attached to the cooling roll side of the present film to obtain an adhesive film in which the film of the present invention and the adhesive layer were laminated.
The separator of the obtained adhesive film was peeled off, and an expansion test was carried out under the above-mentioned expanding conditions. The average expandability at three points in the MD direction was 105.0%, and the average expandability at three points in the TD direction was 103.9%.
Although the material had excellent handleability, it contained a small amount of the specified styrene-based elastomer and did not expand by 110% or more. Therefore, it was determined that the material had poor expandability and would not be able to ensure sufficient chip spacing when used in semiconductor processing applications.

[Comparative Example 2]
Random polypropylene was used as the resin for the surface layer, random polypropylene, low-density polyethylene, and a styrene-based elastomer (A) were used as the resin for the middle layer, and low-density polyethylene was used as the resin for the back layer, in the amounts shown in Table 1. A film consisting of three types and three layers and having a thickness of 80 μm was produced using the film-forming method described above.
The thickness of each layer was set to 4 μm for the surface layer, 68 μm for the middle layer, and 8 μm for the back layer, with the ratio of each thickness being 5% for the surface layer, 85% for the middle layer, and 10% for the back layer. However, due to the influence of the styrene-based elastomer (A) with a small styrene component, the film became too flexible, and elongation of the film due to the influence of the tension during film formation was observed. The thickness fluctuation in the MD direction exceeded ±5%, making it difficult to obtain a film of a stable thickness.

[Comparative Example 3]
The same procedure as in Example 3 was repeated, except that the thickness of each layer was 16 μm for the surface layer, 48 μm for the middle layer, and 16 μm for the back layer, and the ratio of each thickness was 20% for the surface layer, 60% for the middle layer, and 20% for the back layer.
The film had good formability and could be sampled without any significant change in thickness. The film was also not too flexible and was judged to have excellent handleability.
The tensile modulus of the obtained film was 300 MPa, and it was confirmed that the film had sufficient rigidity to be easy to handle. The tensile elongation at break was 650%, and no decrease in the elongation at break due to deterioration of the compatibility between the styrene-based elastomer and the polyolefin-based resin was confirmed.
Next, an acrylic adhesive was applied onto the separator by a comma coating method so that the adhesive layer would have a thickness of 25 μm after drying, and the adhesive layer was formed after drying for 5 minutes in a hot air dryer at 80° C. The adhesive layer side of the prepared separator was attached to the cooling roll side of the present film to obtain an adhesive film in which the film of the present invention and the adhesive layer were laminated.
The separator of the obtained adhesive film was peeled off, and an expansion test was carried out under the above-mentioned expansion condition A. The average expandability at three points in the MD direction was 106.1%, and the average expandability at three points in the TD direction was 107.2%.
Although the material had excellent handling properties and contained the specified amount of the specified styrene-based elastomer, the thickness of the elastomer layer was insufficient and expansion of 110% or more was not observed. Therefore, it was determined that the material had poor expandability and would not be able to ensure sufficient chip spacing when used in semiconductor processing applications.

[Industrial Applicability]
According to the present invention, it is possible to provide a film that has excellent film-forming properties when molding a resin into a film and has excellent expandability of the obtained film. It is also possible to provide an adhesive film for semiconductor manufacturing process that has excellent expandability and can ensure sufficient spacing between chips.

Claims (6)

A multi-layer film having at least two or more layers,
At least one layer is an elastomer layer containing polyethylene, polypropylene, and a styrene-based elastomer;
The styrene-based elastomer has a styrene component content of 20% by mass or more and 60% by mass or less,
When the total amount of the resin constituting the elastomer layer is taken as 100% by mass, the content of the styrene-based elastomer is 60% by mass or more, and the thickness ratio of the elastomer layer to the total thickness of the multilayer film is 70% or more,
The sheet has a two-layer, three-layer structure, with a layer mainly made of polyolefin resin as the front and back layers and the elastomer layer as the middle layer,
The surface layer is a layer mainly composed of polypropylene, and the back layer is a layer mainly composed of polyethylene, the polypropylene contained in the surface layer is random polypropylene or homopolypropylene, and the polyethylene contained in the back layer is low-density polyethylene.
Multi-layer film. The multilayer film according to claim 1, having a total thickness of 150 μm or less. 3. The multilayer film according to claim 1, wherein the polyethylene contained in the elastomer layer is a low density polyethylene. The multilayer film according to any one of claims 1 to 3, wherein the polypropylene contained in the elastomer layer is a random polypropylene or a homopolypropylene. An adhesive film comprising a multilayer film according to any one of claims 1 to 4 and an adhesive layer provided on at least one surface of the multilayer film. The adhesive film for semiconductor manufacturing process according to claim 5, which is used in the semiconductor manufacturing process.