JP7845845B2 - Multilayer films, adhesive films, adhesive films for semiconductor manufacturing processes, and protective films - Google Patents

Description

This invention relates to a multilayer film suitably used as a base material for adhesive films (tapes) used in semiconductor manufacturing processes, decorative adhesive films (tapes) such as stickers, labels, and marking films applied to signs, automobiles, etc., or decorative sheets; an adhesive film having an adhesive layer provided on the multilayer film; and a protective film for the adhesive layer side of an adhesive film used in semiconductor manufacturing processes that utilizes the multilayer film.

Traditionally, polyvinyl chloride resin films (hereinafter also referred to as "PVC films") have been widely used as the base material for decorative adhesive films (tapes) used in semiconductor manufacturing processes, stickers, labels, and marking films applied to signs, automobiles, etc., to enhance their aesthetic appeal. These films offer superior colorability, processability, scratch resistance, and weather resistance.

The above-mentioned PVC-based films possess inherent rigidity, but plasticizers are added to impart flexibility so that they can function as adhesive films. However, depending on the plasticizer used, poor compatibility with adhesives can lead to problems such as poor stability when used as an adhesive film and significant plasticizer bleed-out. Furthermore, there is a growing trend towards stricter regulations on the use of plasticizers.
Therefore, polyolefin resin films have been widely used as an alternative material to PVC films.

Furthermore, in the semiconductor manufacturing process, adhesive films for semiconductor wafer processing are used when cutting semiconductor wafers and packages, and due to the problems mentioned above, the use of polyolefin resin films is increasing.
Films using PVC-based and polyolefin-based resins have been developed for use in semiconductor manufacturing processes (for example, Patent Document 1).

In recent years, with the miniaturization and thinning of semiconductor devices, films require not only handling ease and flexibility during expansion, but also heat resistance. This is necessary to prevent chip damage and loss during expansion. Because heating processes are anticipated, such as heating the wafer and adhesive film to create a stronger bond, or heating the expansion process after dicing, heat resistance is sometimes required for films used in semiconductor manufacturing processes.

Furthermore, in addition to blade dicing using rotating blades, there are cases where suitability for processes such as stealth dicing, which involves modifying a portion of the semiconductor wafer by irradiating it with laser light and then stretching the wafer to divide it, is required. In stealth dicing, a certain amount of force needs to be applied to the wafer to divide it, so in some cases, the adhesive film's base material also needs to have a certain degree of strength so that the adhesive film can apply the necessary force for division.

Patent Document 2 discloses a dicing substrate film using a polyethylene resin to maintain expandability even at low temperatures.
Furthermore, Patent Document 3 discloses a substrate film for semiconductor manufacturing processes, comprising a resin composition containing homopolypropylene, a polymer-type antistatic agent, and a thermoplastic elastomer in predetermined proportions, which provides antistatic properties and excellent flexibility and heat resistance.

However, the film described in Patent Document 2 uses only polyethylene-based resins with relatively low melting points. While it appears to have excellent low-temperature expandability, there is room for improvement in its heat resistance. Furthermore, the film described in Patent Document 3, while excellent in antistatic properties and heat resistance, does not possess sufficient tensile modulus, leaving room for improvement for applications requiring greater strength during expansion.

Japanese Patent Application Publication No. 09-008111 Japanese Patent Publication No. 2018-125521 Japanese Patent Publication No. 2020-84143

In view of the above problems, the present invention aims to provide a multilayer film that possesses sufficient heat resistance even when heating is anticipated in the semiconductor manufacturing process, and that has a certain degree of strength and flexibility, making it applicable to multiple anticipated dicing processes such as blade dicing and stealth dicing. Furthermore, the present invention aims to provide a multilayer film that can be suitably used in semiconductor manufacturing processes by providing an adhesive layer to the multilayer film, and that can also be used as a protective film for the adhesive layer side of an adhesive film for semiconductor manufacturing processes.

The inventors diligently studied multilayer films possessing heat resistance, strength, and flexibility by using specific polyolefin resins in each layer, and as a result, have completed the present invention.

In other words, the gist of this invention is as follows:
[1]
A multilayer film having at least a surface layer and a back layer, and containing a polyolefin resin, wherein the tensile modulus of at least one of the surface layer and the back layer is 50 MPa or more and 500 MPa or less, and the tensile modulus of the multilayer film is 500 MPa or more and 900 MPa or less.
[2]
The polyolefin resin is selected from the group consisting of polypropylene resin, polyethylene resin, olefin elastomer, and a combination of two or more of these, as described in [1].
[3]
The multilayer film according to [1] or [2], wherein the resin composition constituting each layer of the multilayer film further contains a styrene-based elastomer.
[4]
A multilayer film according to any one of claims [1] to [3], wherein the content of styrene-based elastomer in each resin composition constituting the surface layer and the back layer is greater than the content of styrene-based elastomer in the resin composition constituting the layer located between the surface layer and the back layer.
[5]
A multilayer film according to any one of [1] to [4], containing a polyolefin resin having a crystal melting peak of 120°C or higher.
[6]
An adhesive film having an adhesive layer on at least one side of a multilayer film as described in any one of items [1] to [5].
[7]
[6] An adhesive film for semiconductor manufacturing processes using the adhesive film described above.
[8]
A protective film for the adhesive layer side of an adhesive film for semiconductor manufacturing processes using a multilayer film as described in any one of items [1] to [5].

By using the multilayer film of the present invention, it is possible to provide a multilayer film with sufficient heat resistance even when heating is anticipated in the semiconductor manufacturing process, and with a certain degree of strength and flexibility that can be applied to multiple anticipated dicing processes such as blade dicing and stealth dicing. Furthermore, this film can be suitably used in applications such as films for semiconductor manufacturing processes and protective films for the adhesive layer side of adhesive films for semiconductor manufacturing processes.

The present invention will be described in detail below, but the present invention is not limited to the embodiments described below and can be implemented with various modifications within the scope of its gist. Furthermore, when the expression "~" is used in this specification, it shall be used to include the numerical values or physical properties before and after it.

The present invention relates to a multilayer film having at least a surface layer and a back layer, containing a polyolefin resin, characterized in that at least one of the surface layer and the back layer has a tensile modulus of 50 MPa or more and 500 MPa or less, and the multilayer film has a tensile modulus of 500 MPa or more and 900 MPa or less.

The multilayer film of the present invention contains a polyolefin resin. By using a polyolefin resin, it is possible to impart appropriate heat resistance, strength, and flexibility to the multilayer film.
Examples of polyolefin resins include polypropylene resins, polyethylene resins, olefin elastomers, cyclic olefin resins, and polymethylpentene resins, which will be discussed later. Among these, polypropylene resins, polyethylene resins, and olefin elastomers are preferred in terms of their availability and the ease with which various properties can be imparted and adjusted.

Examples of polypropylene resins include homopolymers of propylene (homopolypropylene), copolymers of propylene as the main component with other monomers copolymerizable with propylene, and mixtures thereof.
Examples of copolymers of propylene as the main component with other monomers copolymerizable with propylene include random copolymers (random polypropylene) and block copolymers (block polypropylene) of propylene and ethylene or other α-olefins, block copolymers or graft copolymers containing rubber components, and the like.
As other monomers copolymerizable with propylene, α-olefins having 4 to 12 carbon atoms are preferred, such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 4-methyl-1-pentene, and 1-decene, and one or more of these can be used.

The crystal melting peak of the polypropylene resin is preferably 120°C or higher. Having a crystal melting peak of 120°C or higher makes it possible to impart sufficient heat resistance to the resulting multilayer film. More preferably 125°C or higher, and even more preferably 130°C or higher.
From the viewpoint of availability, heat resistance, and flexibility, it is preferable to use homopolypropylene or random polypropylene among the above-mentioned polypropylene resins, and more preferably to use homopolypropylene.

Examples of commercially available random polypropylene products include Novatec PP "FW4BA" and Novatec PP "FX3B" (both manufactured by Nippon Polypropylene Co., Ltd.), PC630A and PC630S (both manufactured by Sun Allomer Co., Ltd.), F-730NV and F-744NP (both manufactured by Prime Polypropylene Co., Ltd.), Sumitomo Noblen "FL6737" and Sumitomo Noblen "S131" (both manufactured by Sumitomo Chemical Co., Ltd.).

Examples of commercially available homopolypropylene products include Novatec PP "MA3U", Novatec PP "FY6HA" (both manufactured by Nippon Polypropylene Co., Ltd.), PC412A, PC600A (both manufactured by Sun Allomer Co., Ltd.), F113G, F-704NP (both manufactured by Prime Polypropylene Co., Ltd.), Sumitomo Noblen "FLX80E4", Sumitomo Noblen "FLX80H5", and Sumitomo Noblen "WF836DG3" (all manufactured by Sumitomo Chemical Co., Ltd.).
The above-mentioned polypropylene resins may be used individually 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, as well as the strength, flexibility, handling, and expandability of the resulting film.

Examples of polyethylene resins include ethylene homopolymers, copolymers of ethylene as the main component with other monomers copolymerizable with ethylene (low-density polyethylene (LDPE), high-pressure low-density polyethylene, linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), ethylene copolymers obtained by polymerization using metallocene catalysts (metallocene polyethylene), ethylene-vinyl acetate copolymers, ethylene-(meth)acrylate copolymers, ethylene-(meth)acrylate ethyl copolymers, ethylene-(meth)acrylate butyl copolymers, ethylene-(meth)acrylate copolymers, and metal ion crosslinked resins (ionomers) of ethylene-(meth)acrylate copolymers.
In particular, from the viewpoint of ease of availability, ease of handling of the resin, and ease of adjusting the heat resistance and flexibility of the resulting film, it is preferable to use high-density polyethylene (HDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE), and it is more preferable to use high-density polyethylene (HDPE) and low-density polyethylene (LDPE).

Examples of commercially available high-density polyethylene include Novatec HD "HF560" and Novatec HD "HF562" (both manufactured by Nippon Polyethylene Co., Ltd.), and Suntec HD "F371" and Suntec HD "J340" (both manufactured by Asahi Kasei Corporation).

Examples of commercially available low-density polypropylene include Novatec LD "LC500", Novatec LD "LC520", Novatec LD "LC720" (all manufactured by Nippon Polyethylene Co., Ltd.), F224N, F324C, F522N (all manufactured by Ube Maruzen Polyethylene Co., Ltd.).
The polyethylene resins described above may be used individually or in combination of two or more types. They can be appropriately selected as needed, taking into consideration the film-forming properties, flexibility, handling, and expandability of the resulting thermoplastic resin film.

Olefin-based elastomers are soft resins comprising a polyolefin resin and a rubber component. The rubber component may be dispersed in the polyolefin resin, or the two may be copolymerized.
Specific examples of olefin-based elastomers 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 their derivatives and acid-modified derivatives.

Examples of commercially available olefin-based elastomers include Wellnex "RFG4VM", Wellnex "RFX4V", Wellnex "RMG02" (all manufactured by Nippon Polypropylene Co., Ltd.), Tuffmer "A-4070S", Tuffmer "A-4085S", Tuffmer "BL2481M", Tuffmer "BL3450M", Tuffmer "XM7070", Tuffmer "XM7080", and Milastomer (all manufactured by Mitsui Chemicals, Inc.).

The melt flow rates of the aforementioned polypropylene resins, polyethylene resins, and olefin elastomers are appropriately selected depending on the molding method and application, but it is preferable that the value measured at a temperature of 190°C or 230°C with a load of 2.16 kg is 0.1 to 50 g/10 min. A value of 0.1 g/10 min or higher results in good film moldability, while a value of 50 g/10 min or lower allows for good film thickness accuracy. More preferably, the value is 0.5 to 40 g/10 min, and even more preferably 1.0 to 30 g/10 min.

Regarding the strength of polypropylene resins, polyethylene resins, and olefin elastomers, it is preferable that the tensile modulus of the film obtained from these resins alone is in the range of 50 to 2000 MPa. A tensile modulus within the range of 50 to 2000 MPa makes it possible to impart appropriate strength and flexibility to the film of the present invention. More preferably, it is in the range of 50 to 1500 MPa, and even more preferably, in the range of 50 to 1000 MPa.

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

As the polymethylpentene resin, it is preferable to use a homopolymer or copolymer with other monomers that uses methylpentene as a monomer. A specific example is a copolymer of α-olefin and 4-methylpentene-1, which was exemplified as another monomer copolymerizable with propylene for polypropylene resins.
When the polymethylpentene resin is a copolymer, it is preferable that the content of the α-olefin component used in copolymerization is 20% by mass or less. By limiting it to 20% by mass or less, it is possible to suppress the decrease in the crystal melting peak. More preferably, it is 10% by mass or less.

The multilayer film of the present invention may contain various thermoplastic resins in addition to the polyolefin resin described above. Among thermoplastic resins, styrene elastomers are preferred from the viewpoint of compatibility with polyolefin resins and imparting flexibility to the film.
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 represented by styrene (hereinafter referred to as the styrene component), and in formula (I), the degree of polymerization may be the same or different at both ends of the molecular chain. Furthermore, Y is at least one selected from butadiene polymer blocks, isoprene polymer blocks, butadiene/isoprene copolymer blocks, hydrogenated butadiene polymer blocks, hydrogenated isoprene polymer blocks, hydrogenated butadiene/isoprene copolymer blocks, partially hydrogenated butadiene polymer blocks, partially hydrogenated isoprene polymer blocks, and partially hydrogenated butadiene/isoprene copolymer blocks. Also, n is an integer of 1 or more.

Specific examples of styrene-based elastomers include styrene-ethylene-butylene-styrene copolymers, styrene-ethylene-propylene-styrene copolymers, styrene-ethylene-ethylene-propylene-styrene copolymers, styrene-butadiene-butene-styrene copolymers, styrene-butadiene-styrene copolymers, styrene-isoprene-styrene copolymers, styrene-hydrogenated butadiene diblock copolymers, styrene-hydrogenated isoprene diblock copolymers, styrene-butadiene diblock copolymers, and styrene-isoprene diblock copolymers. Among these, styrene-ethylene-butylene-styrene copolymers, styrene-ethylene-propylene-styrene copolymers, styrene-ethylene-ethylene-propylene-styrene copolymers, and styrene-butadiene-butene-styrene copolymers are preferred. Block copolymers of styrene-ethylene-butylene-crystalline olefin copolymers can also be used.

The melt flow rate of the styrene-based elastomer (measured at a temperature of 230°C and a load of 2.16 kg) is preferably 0.1 to 20 g/10 min, more preferably 0.15 to 19 g/10 min, and particularly preferably 0.2 to 18 g/10 min. A melt flow rate of 0.1 g/10 min or higher and 20 g/10 min or lower is preferable from the viewpoint of film-forming properties, as it exhibits good compatibility with polyolefin resins, maintains a good film appearance, and allows for easy thickness adjustment.

The styrene content in the styrene-based elastomer is preferably 50% by mass or less. A styrene content of 50% by mass or less makes it possible to impart flexibility to the resulting film while maintaining its strength. Preferably, it is 45% by mass or less, and more preferably 40% by mass or less.
The styrene content and the content of other components can be measured using ^1H -NMR or ^13C -NMR. Here, "styrene content" refers to the percentage (mass%) of aromatic vinyl polymer blocks, represented by styrene, based on the mass of the styrene-based elastomer.

Examples of commercially available styrene-based elastomers with a styrene content of 50% by mass or less include ToughTec H1221, ToughTec H1062, ToughTec H1521, ToughTec H1052, ToughTec H1051, ToughTec H1517, ToughTec P1083, ToughTec P5051 (all manufactured by Asahi Kasei Corporation), Septon 1020, Septon 2002, Septon 2004F, Septon 2063, Septon 8007L, Hybrar 7311, Hybrar 7311F, Hybrar 7125F, Hybrar 5127, Hybrar 5125 (all manufactured by Kuraray Co., Ltd.), and Dynalon 1320P, Dynalon 4600P, Dynalon 8300P, Dynalon 8903P (all manufactured by JSR Corporation).
The styrene-based elastomers described above may be used individually 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 thermoplastic resin film, as well as the flexibility, handling, and expandability of the resulting film.

<Other ingredients>
Various additives can be incorporated into the multilayer film of the present invention to provide properties such as antistatic properties, heat resistance, and weather resistance.
For example, antistatic agents, antioxidants, neutralizing agents, lubricants, antiblocking agents, plasticizers, heat stabilizers, light stabilizers, dyes and pigments, nucleating agents, ultraviolet absorbers, fillers, inorganic fillers that impart rigidity, and elastomers other than those mentioned above that impart flexibility may be used, to the extent that they do not hinder the effects of the present invention.

Known polymeric antistatic agents can be used; for example, a block copolymer of a hydrophobic block and a hydrophilic block can be used. In polymeric antistatic agents, the hydrophobic block and the hydrophilic block form a block copolymer through ester bonds, ether bonds, amide bonds, imide bonds, urethane bonds, and urea bonds, etc.

As UV absorbers, known types can be used, such as benzotriazole-based UV absorbers, benzophenone-based UV absorbers, and triazine-based UV absorbers.

As a light stabilizer, known substances can be used, such as hindered amine-based light stabilizers.

For lubricants and antiblocking agents, silicone-olefin copolymers are preferable because they exhibit excellent compatibility with the aforementioned polypropylene-based resins, polyethylene-based resins, etc., and enable the creation of films with surface defects such as bleed-out and long-term scratch resistance and slipperiness.

<Double-layer film>
The present invention relates to a multilayer film containing a polyolefin resin, characterized in that it has at least a surface layer and a back layer, at least one of the surface layer and the back layer has a tensile modulus of 50 MPa or more and 500 MPa or less, and the multilayer film has a tensile modulus of 500 MPa or more and 900 MPa or less.

By having at least one of the surface and back layers have a tensile modulus of 50 MPa or more and 500 MPa or less, it becomes possible to impart appropriate flexibility and expandability to the resulting multilayer film.
Here, "the tensile modulus of at least one of the surface and back layers being 50 MPa or more and 500 MPa or less" means that when a film is prepared consisting only of the resin composition constituting at least one of the surface and back layers, the tensile modulus of the film is 50 MPa or more and 500 MPa or less.
It is possible to appropriately select whether to keep only one of the layers, the surface layer or the back layer, within the above-mentioned range of tensile modulus, or to keep both the surface and back layers within the above-mentioned range of tensile modulus. Furthermore, when both the surface and back layers are within the above-mentioned range of tensile modulus, the resin compositions of the surface layer and the back layer may be different or the same. From the viewpoint of film-forming properties and the simplicity of the resin used, it is preferable that the surface layer and the back layer have the same resin composition. A tensile modulus within the range of 50 MPa to 450 MPa is more preferable, and a tensile modulus within the range of 50 MPa to 400 MPa is even more preferable.

The multilayer film must have a tensile modulus of 500 MPa to 900 MPa, in addition to the tensile modulus of its front and back layers. By having a tensile modulus of 50 MPa to 500 MPa for at least one of the front and back layers, and a tensile modulus of 500 MPa to 900 MPa for the multilayer film, it is possible to create a multilayer film with a flexible layer while maintaining appropriate strength throughout. A tensile modulus of 500 MPa to 850 MPa is more preferable, and a tensile modulus of 500 MPa to 800 MPa is even more preferable.

The polyolefin resin contained in the multilayer film of the present invention is selected from the group consisting of polypropylene resins, polyethylene resins, olefin elastomers, and combinations of two or more of these. Details of the polypropylene resins, polyethylene resins, and olefin elastomers are as described above.
In the multilayer film of the present invention, it is preferable to use the aforementioned styrene-based elastomer to adjust the tensile modulus of at least one of the surface layer and the back layer, and the multilayer film. Furthermore, when a styrene-based elastomer is used, it is preferable that the content of the styrene-based elastomer in each resin composition constituting the surface layer and the back layer is greater than the content of the styrene-based elastomer in the resin composition constituting the layer located between the surface layer and the back layer. By setting the content of the styrene-based elastomer in the resin compositions constituting the surface layer, the back layer and the intermediate layer as described above, it is possible to easily adjust the tensile modulus of the surface layer and the back layer, and the tensile modulus of the multilayer film. When a styrene-based elastomer is contained in the multilayer film, if the total amount of each thermoplastic resin constituting the surface layer and the back layer is 100% by mass, it is preferable that the styrene-based elastomer is 10% by mass or more and 50% by mass or less. By setting the styrene-based elastomer to 10% by mass or more and 50% by mass or less, flexibility can be imparted to the surface layer and the back layer, and problems such as blocking between films and poor transport during film formation due to excessive flexibility can be suppressed. More preferably, it is within the range of 10% by mass or more and 45% by mass or less, and even more preferably, within the range of 10% by mass or more and 40% by mass or less. Furthermore, if the total amount of thermoplastic resin constituting the intermediate layer is 100% by mass, it is preferable that the amount of styrene-based elastomer is less than the amount in the front and back layers and is between 3% by mass and 20% by mass or less. It is preferable to set it to 1% by mass or more and 20% by mass or less because it can suppress the entire multilayer film from becoming too flexible. More preferably, it is between 1% by mass and 17% by mass or less, and even more preferably, between 1% by mass and 14% by mass or less.

The basic structure of the multilayer film of the present invention is as follows.
(1) A two-layer film comprising a layer with a tensile modulus of 50 MPa or more and 500 MPa, and a layer with a tensile modulus of 500 MPa or more and 900 MPa or less.
(2) A three-layer film comprising a layer with a tensile modulus of 50 MPa to 500 MPa (surface layer), a layer with a tensile modulus of 500 MPa to 900 MPa (intermediate layer), and a layer with a tensile modulus of 50 MPa to 500 MPa (back layer).
In the three-layer film configuration of (2), the polypropylene resins constituting the surface layer and the back layer may have the same composition or different compositions.
Furthermore, in the configuration of (2), the intermediate layer may consist of two or more layers. In that case, the configuration of (2) also includes a film configuration consisting of three or more layers.

The thickness of the multilayer film of the present invention is preferably 30 to 250 μm. A thickness of 30 μm or more ensures good film-forming properties during production and good handling of the resulting film. A thickness of 250 μm or less allows for good handling and process passability of the film during the lamination process of printing and adhesive layers. More preferably, the thickness of the multilayer film of the present invention is 35 to 230 μm, and even more preferably 40 to 210 μm.

The tensile elongation at break of the multilayer film of the present invention is preferably 300% or more. A tensile elongation of 300% or more is preferable because it suppresses problems due to breakage even when the film is subjected to adhesive processing, and furthermore, it reduces the likelihood of breakage during the expansion process in semiconductor manufacturing. More preferably, it is 400% or more, and even more preferably 500% or more. Furthermore, when used as a protective film for the printed layer or adhesive layer, a tensile elongation of 300% or more suppresses problems during transport and handling.

While known methods can be used to form the multilayer film of the present invention, melt extrusion molding is preferred. Among melt extrusion molding methods, T-die molding, in which molten resin is extruded from an extruder with a T-die and then cooled and solidified to obtain the film, is more preferred.

To obtain a multilayer film, it is preferable to use a co-extrusion T-die molding method utilizing multiple extruders. By using a co-extrusion T-die molding method utilizing multiple extruders, it becomes possible to obtain a multilayer film, and the resin composition preferred for the surface layer of the present invention can be applied to only one side of the film or to both sides.

Co-extrusion T-die molding methods include a method using a multi-manifold die to form multiple resin layers into a film, then bringing them into contact within the T-die to create a multilayer film, and a method using a device called a feed block to combine molten resins, allowing them to adhere to each other before obtaining a multilayer film.

The film may be surface-treated on one or both sides as needed, using methods such as plasma treatment, corona treatment, ozone treatment, and flame treatment. Depending on the intended use of the resulting film, it is possible to choose whether to surface-treat one or both sides. Furthermore, when used as a protective film for the aforementioned printed or adhesive layers, surface treatment is preferable because the protective film needs to be peeled off after lamination.

Furthermore, it is preferable that the thickness of the surface layer be within the range of 1 to 50% of the total film thickness. By keeping it within this range, it is possible to impart sufficient strength to the resulting multilayer film without compromising its flexibility. More preferably, it is within the range of 1 to 40% of the total film thickness, and even more preferably, within the range of 1 to 30%.

<Adhesive film>
The multilayer film of the present invention can be made into an adhesive film by providing an adhesive layer on at least one of its front or back surfaces (hereinafter also referred to as "the adhesive film of the present invention").

The adhesive used in 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. Furthermore, a functional layer such as an adhesive layer or a thermosetting resin layer may be provided on top of the adhesive layer.

The adhesive layer can be provided by directly coating the multilayer film with adhesive. Alternatively, the adhesive layer can be laminated onto a separator with a release layer, and then the adhesive layer side is bonded to the surface layer of the multilayer film of the present invention, thereby transferring the adhesive layer.

In the adhesive film of the present invention, the above-described surface treatment may be performed on one or both sides of the film before the adhesive layer is applied. Furthermore, a primer layer may be provided between the film and the adhesive layer, if necessary.
The thickness of the adhesive layer and primer layer can be determined as needed.

<Protective film>
The multilayer film of the present invention can be used as a protective film for protecting the printed layer or adhesive layer of a film having a printed layer or adhesive layer on at least one of its front or back surfaces.
When a film with laminated printing and adhesive layers is wound up as is, the printing and adhesive can transfer to the back of the film. Therefore, a protective film is sometimes laminated to the side of these coatings to prevent transfer and to allow sufficient time for curing.
The multilayer film of the present invention is characterized in that at least one of the surface and back layers has a tensile modulus of 50 MPa or more and 500 MPa or less, and the multilayer film has a tensile modulus of 500 MPa or more and 900 MPa or less. The film surface has high flexibility, and the film can easily follow the surface of the coating, which is expected to have the advantage of making it less likely for air bubbles to remain between the coating and the film. In addition, because the surface side is flexible, the film can easily follow the irregularities on the coating side, and a certain degree of adhesion can be ensured, making it possible to suppress problems such as the film peeling off unintentionally before re-peeling.

Because the multilayer film of the present invention contains a polyolefin resin, it has poor adhesion to printed layers and adhesive layers, and is re-peelable, making it suitable for use as a protective film. Furthermore, when used as a protective film, re-peelability is necessary, so it is preferable not to perform surface treatment as described above.
Lamination to the coating film side can be carried out using known methods such as roll-to-roll lamination.

The film of the present invention is a multilayer film that has sufficient heat resistance even when heating is anticipated in the semiconductor manufacturing process, and possesses a certain degree of strength and flexibility that makes it applicable to multiple anticipated dicing processes such as blade dicing and stealth dicing.
Furthermore, by providing an adhesive layer to the multilayer film, it can be made into an adhesive film suitable for use in semiconductor manufacturing processes, and it can also be suitably used as a protective film to protect the printed layer and adhesive layer of a film having a printed layer and an adhesive layer.

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

[Materials used]
The following polyolefin resins (polypropylene resins, olefin elastomers) and styrene elastomers were used as thermoplastic resins, as shown below.

<Polypropylene resin (A-1)>
"MA3U" manufactured by Nippon Polypropylene Co., Ltd. (homopolypropylene, melt flow rate at 230°C and 2.16 kg: 11 g/10 min, crystal melting peak: 160°C, tensile modulus of single film: 1000 MPa)
<Polypropylene resin (A-2)>
Sun Allomer Co., Ltd., "PC630A" (random polypropylene, melt flow rate at 230°C, 2.16 kg: 7.5 g/10 min, crystal melting peak: 135°C, tensile modulus of single film: 510 MPa)
<Olefin-based elastomer (B-1)>
Wellnex "RFX4V" manufactured by Nippon Polypropylene Co., Ltd. (olefin-based elastomer, melt flow rate at 230°C and 2.16 kg: 6.0 g/10 min, crystal melting peaks: 90°C and 131°C, tensile modulus of single film: 250 MPa)
<Olefin-based elastomer (B-2)>
Wellnex "RFG4VM" manufactured by Nippon Polypropylene Co., Ltd. (olefin-based elastomer, melt flow rate at 230°C and 2.16 kg: 6.0 g/10 min, crystal melting peak: 127°C, tensile modulus of single film: 240 MPa)
<Styrene-based elastomer>
Asahi Kasei Corporation's "ToughTec H1221" (melt flow rate at 230°C, 2.16 kg: 4.5 g/10 min, styrene component content: 12% by mass, styrene-ethylene-butylene-styrene copolymer)

<Preparation of resin composition>
The above thermoplastic resins were blended to a total of 100 parts by mass. When using two or more types, they were mixed by dry blending, and uniform mixing was confirmed by visual inspection.

<Method of film manufacturing>
Each resin composition was loaded into the hopper of three Toshiba Machine single-screw extruders (for the surface layer: 35φ mm, L/D = 25 mm; for the intermediate layer: 50φ mm, L/D = 32 mm; for the back layer: 35φ mm, L/D = 25 mm). The extruder temperature of each extruder was set to 190-230°C. The three layers (surface, intermediate, and back) were combined in the feed block and extruded through a 650 mm wide T-die (temperature setting 210-230°C, lip opening 0.5 mm). The thickness configuration was set according to the thicknesses listed in Table 1, and the rotation speed of each extruder was set accordingly.
The extruded molten resin was cooled and solidified on a winding machine equipped with a mirror-finish cooling roll (cooling roll 700 mm wide x φ350 mm, roll temperature approximately 30°C), then corona treatment was performed on both sides and the material was wound up to obtain a multi-layered film with a thickness of approximately 60 μm, consisting of one type 3-layer or two types 3-layer.
Furthermore, in this invention, the mirror-like surface of the obtained film on the cooling roll side is referred to as the surface layer.

[Thickness of each layer]
The thickness of each layer was determined by calculating the amount of resin extruded from each extruder.

[Total film thickness]
The thickness of the film was measured at the center and both ends using a contact-type thickness gauge, and it was confirmed that the film met the specified thickness.

[Tensile modulus (surface layer only)]
Using only the resin composition of the surface layer of a two-type, three-layer multilayer film, a film consisting substantially only of the surface resin composition of one type, three-layer film was prepared using the aforementioned film-forming method (hereinafter also referred to as "surface-only film").
Test specimens were taken from the film using a dumbbell "SDK-600" manufactured in accordance with JIS K6732, and the tensile modulus (MPa) was measured at a tensile speed of 50 mm/min using an Autograph (AGS-X manufactured by Shimadzu Corporation) under the following conditions, referring to JIS K7127: 23°C, 50% RH atmosphere.
The tensile modulus was measured in the extrusion direction (MD) of the film.

[Tensile modulus of elasticity (multilayer film)]
Test specimens were taken from multilayer films consisting of the resin compositions and layer configurations described in Table 1 using a dumbbell "SDK-600" manufactured in accordance with JIS K6732. The tensile modulus (MPa) was measured at a tensile speed of 50 mm/min using an Autograph (AGS-X, Shimadzu Corporation) under the following conditions, referring to JIS K7127: 23°C, 50% RH atmosphere.
The tensile modulus was measured in the extrusion direction (MD) of the film.

[Tensile elongation at fracture]
Test specimens were taken from multilayer films consisting of the resin compositions and layer configurations described in Table 1 using a dumbbell "SDK-600" manufactured in accordance with JIS K6732. The tensile elongation at break (%) was measured at a tensile speed of 300 mm/min using a small benchtop test machine (Shimadzu EZ-L) under conditions of 23°C and 50% RH.
The tensile elongation at break was measured in the extrusion direction (MD) of the film.

[Crystal melting peak]
Using a differential scanning calorimetry system (DSC823e, Mettler-Toledo), approximately 5 mg of each raw material used in the examples and comparative examples was heated from 25°C to 230°C at a heating rate of 10°C/min, then cooled to 25°C at a cooling rate of 10°C/min, and then heated again to 230°C at a heating rate of 10°C/min. The crystal melting peak was calculated from the charts obtained during these heating cycles.

[Example 1]
Polypropylene resin (A-1), olefin elastomer (B-1), and styrene elastomer were used as thermoplastic resins, and resin compositions were prepared using the blending amounts shown in Table 1.
Using the resin compositions for the surface and back layers and the resin composition for the intermediate layer described in Table 1, a multilayer film with a total thickness of 60 μm was obtained using the aforementioned film-forming method, with two types of three layers having the same resin composition on both the surface and back. The film-forming conditions were adjusted so that the thickness of each layer was 3 μm for the surface layer, 54 μm for the intermediate layer, and 3 μm for the back layer.
The tensile modulus of the surface layer of the film was evaluated by obtaining a substantially single-layer film consisting of one type of resin composition and three layers, using the resin compositions that constitute the surface layer shown in Table 1.
The tensile modulus of the film consisting only of the resin composition constituting the surface layer was 90 MPa, and the tensile modulus of the multilayer film was 630 MPa. Since the surface and back layers of this multilayer film both exhibited a tensile modulus of 90 MPa, falling within the range of 50 MPa to 500 MPa, and the overall tensile modulus of the multilayer film was within the range of 500 MPa to 900 MPa, it was confirmed that it achieved a good balance of flexibility and strength. Furthermore, the tensile elongation at break was 770%, exceeding 300%, confirming a low possibility of defects due to breakage during handling.
Furthermore, it exhibited a 160°C melting peak derived from homopolypropylene, and 131°C and 90°C melting peaks derived from olefin-based elastomers. The presence of melting peaks above 120°C confirmed good heat resistance.
Therefore, it was confirmed that this film possesses sufficient heat resistance, flexibility, and strength.

[Example 2]
Polypropylene resin (A-1), olefin elastomer (B-2), and styrene elastomer were used as thermoplastic resins, and resin compositions were prepared using the blending amounts shown in Table 1.
Using the resin compositions for the surface and back layers and the resin composition for the intermediate layer described in Table 1, a multilayer film with a total thickness of 60 μm was obtained using the aforementioned film-forming method, with two types of three layers having the same resin composition on both the surface and back. The film-forming conditions were adjusted so that the thickness of each layer was 3 μm for the surface layer, 54 μm for the intermediate layer, and 3 μm for the back layer.
The tensile modulus of the surface layer of the film was evaluated by obtaining a substantially single-layer film consisting of one type of resin composition and three layers, using the resin compositions that constitute the surface layer shown in Table 1.
The tensile modulus of the film consisting only of the resin composition constituting the surface layer was 230 MPa, and the tensile modulus of the multilayer film was 650 MPa. Since the surface and back layers of this multilayer film both exhibited a tensile modulus of 230 MPa, falling within the range of 50 MPa to 500 MPa, and the overall tensile modulus of the multilayer film was within the range of 500 MPa to 900 MPa, it was confirmed that it achieved a good balance of flexibility and strength. Furthermore, the tensile elongation at break was 740%, exceeding 300%, confirming a low possibility of defects due to breakage during handling.
Furthermore, it exhibited a crystalline melting peak at 160°C derived from homopolypropylene and a crystalline melting peak at 127°C derived from olefin-based elastomers, and the presence of crystalline melting peaks above 120°C confirmed good heat resistance.
Therefore, it was confirmed that this film possesses sufficient heat resistance, flexibility, and strength.

[Comparative Example 1]
The procedure was the same as in Example 1, except that only a polypropylene-based resin (A-1) was used as the thermoplastic resin for the front and back layers and the intermediate layer.
A film with a total thickness of 60 μm was obtained, which was essentially a single layer consisting of three layers of one type. The film formation conditions were adjusted so that the thickness of each layer was 3 μm for the surface layer, 54 μm for the intermediate layer, and 3 μm for the back layer.
This multilayer film consisted solely of homopolypropylene, and both the surface layer and the entire film had an elastic modulus of 930 MPa. Because the elastic modulus of both the surface and back layers, as well as the film itself, exceeded the desired range, the film was judged to be hard and have poor expandability and handling properties. While the tensile elongation at break was 800% and the crystal melting peak was 160°C, indicating a low probability of failure due to breakage and good heat resistance, the high elastic modulus resulted in poor processability and handling in subsequent processes.

[Comparative Example 2]
Using a polypropylene resin (A-1), an olefin elastomer (B-2), and a styrene elastomer as thermoplastic resins, a substantially single-layer film consisting of one type and three layers, comprising only the surface resin composition, was obtained.
The film deposition conditions were adjusted so that the thickness of each layer was 3 μm for the surface layer, 54 μm for the intermediate layer, and 3 μm for the back layer.
The tensile modulus of the obtained film was 230 MPa for both the surface layer and the entire film. Although the surface layer of this film was within the range of 50 MPa to 500 MPa, the overall modulus of the film was below the range of 500 MPa to 900 MPa, indicating high flexibility and a lack of balance between strength and flexibility. The tensile elongation at break was 730%, and the crystal melting peaks were 160°C, derived from homopolypropylene, and 127°C, derived from olefin-based elastomers. While the possibility of failure due to breakage was low and the heat resistance was good, the low modulus of elasticity resulted in a lack of balance between strength and flexibility.

[Comparative Example 3]
The procedure was carried out in the same manner as in Example 1, except that only a polypropylene-based resin (A-2) was used as the thermoplastic resin for the surface layer and the intermediate layer.
A film with a total thickness of 60 μm was obtained, which was essentially a single layer consisting of three layers of one type. The film formation conditions were adjusted so that the thickness of each layer was 3 μm for the surface layer, 54 μm for the intermediate layer, and 3 μm for the back layer.
This multilayer film consists solely of random polypropylene, and the elastic modulus of both the surface layer and the entire film was 510 MPa. Although the elastic modulus of the intermediate layer is within the range of 500 MPa to 900 MPa, the elastic modulus of the surface and back layers slightly exceeds the desired range, resulting in the film being judged to have poor flexibility, expandability, and handling properties. The tensile elongation at break was 710%, and the crystal melting peak was 135°C, indicating a low possibility of failure due to breakage, and the heat resistance was also good. However, the elastic modulus of the surface and back layers was slightly high, resulting in a lack of balance between strength and flexibility.

[Example 3]
An acrylic adhesive (SK Dyne 1502C, manufactured by Soken Chemical Co., Ltd.) was applied to a separator using the comma-coating method so that the thickness of the adhesive layer after drying was 25 μm. After drying in a hot air dryer at 80°C for 5 minutes, the adhesive layer was formed.
By laminating the adhesive layer side of the fabricated separator to the corona-treated surface side of the film obtained in Example 1, an adhesive film was obtained in which the film of the present invention and the adhesive layer were laminated.
Furthermore, it is presumed that by using this adhesive film, which has excellent adhesion to adhesives and possesses strength and flexibility, as an adhesive film for semiconductor manufacturing processes, it will be possible to suppress defects caused by the peeling of the adhesive from the film.

[Example 4]
By laminating the uncorona-treated surface layer of the multilayer film prepared in Example 2 onto the adhesive layer side of the adhesive film obtained in Example 3, an adhesive film having a protective film on the adhesive layer was obtained.
This protective film has not undergone corona treatment, and its flexible surface provides adequate adhesion while being easily removable. Therefore, it has been confirmed that it is perfectly usable as a protective film.

This invention provides a multilayer film with sufficient heat resistance even when heating is anticipated in the semiconductor manufacturing process, and with a certain degree of strength and flexibility that can be applied to multiple anticipated dicing processes such as blade dicing and stealth dicing. Furthermore, by providing an adhesive layer on the multilayer film, it can be made into an adhesive film suitably usable in semiconductor manufacturing processes, and it is also possible to provide a multilayer film that can be used as a protective film for the adhesive layer.

Claims (6)

A multilayer film having at least a surface layer and a back layer, and containing a polyolefin resin,
The tensile modulus of at least one of the surface and back layers is 50 MPa or more and 500 MPa or less.
Furthermore, the tensile modulus of the multilayer film is 500 MPa or more and 900 MPa or less.
The resin composition constituting each layer of the multilayer film contains a polyolefin resin having a crystal melting peak of 120°C or higher, and a styrene elastomer.
The tensile elongation at break of the multilayer film is 300% or more.
The multi-layer film in question. The polyolefin resin having a crystal melting peak of 120°C or higher is a polypropylene resin, and each layer further contains at least one selected from polyethylene resins and olefin elastomers, according to claim 1. A multilayer film according to any one of claims 1 to 2, wherein the content of styrene-based elastomer in each resin composition constituting the surface layer and the back layer is greater than the content of styrene-based elastomer in the resin composition constituting the layer located between the surface layer and the back layer. An adhesive film having an adhesive layer on at least one surface of a multilayer film according to any one of claims 1 to 3. An adhesive film for semiconductor manufacturing processes using the adhesive film described in claim 4. A protective film for the adhesive layer side of an adhesive film for semiconductor manufacturing processes, using a multilayer film according to any one of claims 1 to 3.