JP7334597B2 - Composite sheet manufacturing method - Google Patents

Description

The present invention relates to a method of manufacturing a composite sheet.

BACKGROUND ART In recent years, composite sheets obtained by dispersing fillers in resins have been used in various fields. For example, in the field of electronic components such as plasma display panels (PDP) and integrated circuit (IC) chips, composite materials obtained by molding a thermally conductive filler (thermally conductive filler) and resin A sheet (thermal conductive sheet) is used. Conventionally, attempts have been made to improve the method of manufacturing the composite sheet.

For example, in Patent Document 1, a powder composition containing a resin and a filler is transported on a substrate and rolled (rolled) by passing through a gap between a pair of rolling rolls to form a composite sheet on the substrate. Techniques for forming are being studied.

JP 2019-156956 A

Here, in recent years, in order to form a composite sheet that can exhibit the properties imparted by the filler more satisfactorily, there has been a demand to increase the content of the filler in the composite sheet. However, in the conventional roll rolling method, if the amount of filler used is increased in order to increase the filler content (for example, to 30% by volume or more), the resin content relatively decreases. A problem arose in that the adhesiveness of the composite sheet was impaired, and the composite sheet was peeled off from the base film during transportation after roll rolling.
That is, in the above-described conventional techniques, even when the content ratio of the filler in the composite sheet is increased, the phenomenon that the composite sheet is unintentionally peeled off from the base film during transportation is suppressed. There was room for further improvement.

Accordingly, the present invention provides a method for producing a composite sheet, which can suppress peeling of the composite sheet from the base film during transportation even when the filler content in the composite sheet is increased. for the purpose.

The inventor of the present invention has made intensive studies in order to achieve the above object. Further, the present inventors have found that when a composite sheet is formed by roll-rolling the powder composition on the base film while conveying the base film, peeling of the composite sheet from the base film is The inventors paid attention to the fact that the starting point is the downstream end in the conveying direction. After that, the present inventor placed a highly adhesive sheet (adhesive sheet) on the base film so as to precede the powder composition and rolled it, so that the downstream end of the composite sheet in the conveying direction and the adhesive sheet The inventors have found that separation of the composite sheet from the base film can be suppressed by conveying the composite sheet in a bonded state, and completed the present invention.

That is, an object of the present invention is to advantageously solve the above problems, and a method for producing a composite sheet according to the present invention comprises a base film, a resin and a filler supplied on the base film. The powder composition containing is conveyed, and the powder composition is rolled by passing through the gap between a pair of rolling rolls, and the content of the filler is 30% by volume on the base film. A method for manufacturing a composite sheet, including the step of forming the composite sheet as described above, wherein the rolling is performed on the same surface as the powder composition and the powder composition on the base film. and a pressure-sensitive adhesive sheet disposed downstream of the powder composition in the conveying direction of the base film is continuously passed through the gap, and the composite sheet is joined to the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet after rolling has a higher adhesive strength to the base film than the composite sheet to the base film. By using such a method, even when a composite sheet having a filler content of 30% by volume or more is formed on a base film, the composite sheet is prevented from peeling off from the base film. be able to.
In addition, in the present invention, the "adhesive strength to the base film" can be measured using the method described in Examples.

Here, in the method for producing a composite sheet of the present invention, it is preferable that the filler contained in the composite sheet is a particulate material having a volume average particle size of 100 μm or less. If the volume average particle size of the filler in the composite sheet is equal to or less than the above value, it is possible to sufficiently secure the flexibility of the composite sheet even when the content ratio of the filler in the composite sheet is increased. can.
In addition, in the present invention, the "volume average particle size" can be measured using the method described in Examples.

In the method for producing a composite sheet of the present invention, the filler is preferably a scaly particulate material. If a scale-like particulate material is used as the filler, a composite sheet having sufficiently excellent properties such as thermal conductivity can be obtained.

Further, in the method for producing a composite sheet of the present invention, the thickness of the pressure-sensitive adhesive sheet in a state of being pressed in the thickness direction under conditions of 0.2 MPa and 50 ° C. is T _P , and the thickness of the pressure-sensitive adhesive sheet before the pressure is The following formula (1) when T ₀ is used:
Compression ratio={1-(T _P /T ₀ )}×100(%) (1)
It is preferable that the compression rate of the pressure-sensitive adhesive sheet before the rolling, which is calculated by the above, is 5% or more. A pressure-sensitive adhesive sheet having a compressibility equal to or higher than the above-mentioned value can be easily deformed by rolling, and can adhere well to a substrate film or the like. Therefore, it is possible to further suppress the separation of the composite sheet, which is conveyed while being bonded to the pressure-sensitive adhesive sheet, from the base film.
In the present invention, the "compression ratio" is a value derived from the above formula (1), and more specifically, it can be derived using the method described in the examples.

Furthermore, in the method for producing a composite sheet of the present invention, it is preferable that the pressure-sensitive adhesive sheet after rolling has an adhesive strength of 0.3 N or more and 10 N or less to the base film. After rolling, if the adhesive strength of the pressure-sensitive adhesive sheet to the base film is within the range described above, it is possible to further suppress the separation of the composite sheet, which is conveyed while being bonded to the pressure-sensitive adhesive sheet, from the base film. can. In addition, the phenomenon in which the pressure-sensitive adhesive sheet unintentionally follows the opposite rolling roll side (rolling roll surface, or if a cover film described later is used, the cover film surface) instead of the base film side is sufficiently prevented. can be suppressed.

Here, in the manufacturing method of the composite sheet of the present invention, the thickness of the composite sheet can be 800 μm or more. A composite sheet with a large thickness bends more when passing through feed rolls than a composite sheet with a small thickness, and thus is easily peeled off from the base film during transportation. However, according to the method for producing a composite sheet of the present invention, even if the thickness of the composite sheet is equal to or greater than the value described above, peeling of the composite sheet from the base film during transportation can be sufficiently suppressed.
In addition, in the present invention, the "thickness" of a sheet or the like can be measured using the method described in Examples.

Further, in the method for producing a composite sheet of the present invention, it is preferable that the thickness of the pressure-sensitive adhesive sheet before the rolling is greater than the width of the gap. If the thickness of the pressure-sensitive adhesive sheet before rolling is greater than the gap width between the pair of rolling rolls, the pressure-sensitive adhesive sheet is sufficiently compressed during rolling, and can adhere well to the base film. Therefore, it is possible to further suppress the separation of the composite sheet, which is conveyed while being bonded to the pressure-sensitive adhesive sheet, from the base film.

According to the manufacturing method of the composite sheet of the present invention, even when the content of the filler in the composite sheet is increased, the separation of the composite sheet from the base film during transportation can be suppressed.

(a) and (b) are flow diagrams of a method for manufacturing a composite sheet according to an embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.
The method for producing a composite sheet of the present invention can be used to produce a composite sheet having a filler content of 30% by volume or more using a powder composition containing a resin and a filler.

In the method for producing a composite sheet of the present invention, the base film and the powder composition on the base film are conveyed and passed through a gap between a pair of rolling rolls to roll the powder composition. A composite sheet is formed on the base film.
Here, one of the major characteristics of the manufacturing method of the composite sheet of the present invention is that an adhesive sheet is used in the rolling. More specifically, the rolling is performed by applying the powder composition and an adhesive sheet on the same surface as the supply surface of the powder composition on the base film and on the downstream side of the base film in the conveying direction. It is carried out by continuously passing through the gap. By rolling the adhesive sheet and the powder composition in this order, the composite sheet is formed in a state of being joined to the adhesive sheet positioned downstream in the conveying direction. Since the adhesive sheet is present at the downstream end in the transport direction, the composite sheet is less likely to be peeled off from the end even if bending occurs during transport.

An example of the steps of forming a composite sheet in the method for manufacturing a composite sheet of the present invention will be described with reference to FIG. In addition, the manufacturing method of the composite sheet of the present invention is not limited to this example.

In the example shown in FIG. 1, a long base film 1 is sent out in the direction of arrow F (conveyance direction) by rotating the roll 2 of the base film 1, and is spaced apart with a gap. It is supplied to a pair of rolling rolls (rolling roll 31 and rolling roll 32). Here, in FIG. 1(a), an adhesive sheet 4 is placed on a base film 1, and a powder composition 6 is supplied by a powder feeder 5 from behind the adhesive sheet 4 (upstream side in the conveying direction). be done. Then, the adhesive sheet 4 and the powder composition 5 pass through a gap between a pair of rolling rolls (rolling roll 31 and rolling roll 32) continuously while the adhesive sheet 4 precedes, so that the powder composition 5 is rolled. Thus, the composite sheet 7 is formed on the base film 1 . In FIG. 1, a long cover film 8 is used that follows the rotation of the roll while being in contact with the surface of the rolling roll 32, and the powder composition 6 is rolled between the base film 1 and the cover film 8. It is
The long (for example, 1 m or longer) composite sheet 7 thus formed is joined (continuously) to the preceding adhesive sheet 4 as shown in FIG. 1(b). The composite sheet 7 having the adhesive sheet 4 at the downstream end in the conveying direction can be separated from the base film 1 even by bending or the like when passing through the feed roll 9 due to the contribution of the adhesive sheet 4 having a large adhesive force to the base film 1. It can be conveyed stably without peeling off. The obtained composite sheet 7 can be recovered by being wound up by a winding machine 10 as shown in FIG. 1, for example.

(Powder composition)
A powder composition is a composition containing at least a resin and a filler, and optionally other ingredients.

<Resin>
The resin contained in the powder composition is not particularly limited, and can be appropriately selected according to the application of the composite sheet. Here, as the resin, either a liquid resin or a solid resin can be used, but a liquid resin is preferable from the viewpoint of further suppressing the separation of the composite sheet from the base film during transportation. In addition, resin may be used individually by 1 type, and may use 2 or more types together.

<< liquid resin >>
The liquid resin is not particularly limited as long as it is liquid at normal temperature and normal pressure. For example, a thermoplastic resin that is liquid at normal temperature and normal pressure can be used.
In the present invention, “ordinary temperature” refers to 23° C., and “ordinary pressure” refers to 1 atm (absolute pressure).

If a thermoplastic resin that is liquid at room temperature and normal pressure is used as the liquid resin, the liquid resin and the filler can be uniformly mixed by heating and mixing the liquid resin and the filler in the preparation of the powder composition. can. In addition, by rolling the powder composition under heating, the composite sheet can be adhered well to the substrate film, and peeling of the composite sheet from the substrate film during transportation can be further suppressed.

Here, examples of liquid resins include fluorine resins, silicone resins, acrylic resins, and epoxy resins. These may be used individually by 1 type, and may use 2 or more types together. Above all, the liquid resin preferably contains at least one of a silicone resin and a fluororesin, and more preferably contains a fluororesin. If the liquid resin contains at least one of a silicone resin and a fluororesin, the resulting composite sheet can be improved in flame retardancy. Moreover, if a fluororesin is used as the liquid resin, the heat resistance, oil resistance, and chemical resistance of the resulting composite sheet can be improved.

<<Solid Resin>>
The solid resin is not particularly limited as long as it is not liquid at room temperature and pressure. For example, a thermoplastic resin that is solid at room temperature and pressure and a thermosetting resin that is solid at room temperature and pressure can be used.

[Thermoplastic resin that is solid at normal temperature and pressure]
Examples of thermoplastic resins that are solid under normal temperature and pressure include poly(2-ethylhexyl acrylate), copolymers of acrylic acid and 2-ethylhexyl acrylate, polymethacrylic acid or its esters, polyacrylic acid or its esters. Acrylic resin such as acrylic resin; silicone resin; fluorine resin; polyethylene; polypropylene; ethylene-propylene copolymer; polymethylpentene; Polyethylene terephthalate; Polybutylene terephthalate; Polyethylene naphthalate; Polystyrene; Polyacrylonitrile; Styrene-acrylonitrile copolymer; Acrylonitrile-butadiene copolymer (nitrile rubber); butadiene block copolymers or hydrogenated products thereof; styrene-isoprene block copolymers or hydrogenated products thereof; polyphenylene ethers; modified polyphenylene ethers; polyether sulfone; polyether nitrile; polyether ketone; polyketone; polyurethane; liquid crystal polymer; These may be used individually by 1 type, and may use 2 or more types together.
In addition, in this invention, rubber shall be contained in a "resin."

[Thermosetting resin that is solid at normal temperature and pressure]
Examples of thermosetting resins that are solid under normal temperature and pressure include natural rubber; butadiene rubber; isoprene rubber; nitrile rubber; hydrogenated nitrile rubber; chloroprene rubber; Halogenated butyl rubber; polyisobutylene rubber; epoxy resin; polyimide resin; bismaleimide resin; benzocyclobutene resin; phenol resin; unsaturated polyester; polyphenylene ether; and the like. These may be used individually by 1 type, and may use 2 or more types together.

[Content ratio of resin (liquid resin and solid resin)]
The content of the resin in the powder composition is not particularly limited, and is preferably 35% by mass or more and preferably 95% by mass or less. When the ratio of the resin in the powder composition is 35% by mass or more, moldability can be improved when the powder composition is rolled into a sheet. In addition, the composite sheet can be well adhered to the base film, and peeling of the composite sheet from the base film during transportation can be further suppressed. On the other hand, if the proportion of the resin in the powder composition is 95% by mass or less, blocking between particles in the powder composition can be suppressed.

[Content ratio of liquid resin]
Moreover, the content of the liquid resin in the resin is not particularly limited, and is preferably 60% by mass or more and preferably 90% by mass or less. When the content of the liquid resin in the resin is 60% by mass or more, the moldability can be improved when the powder composition is rolled into a sheet. In addition, the composite sheet can be well adhered to the base film, and peeling of the composite sheet from the base film during transportation can be further suppressed. On the other hand, if the content of the liquid resin in the resin is 90% by mass or less, blocking between particles in the powder composition can be suppressed.

<Filling material>
The filler contained in the powder composition is not particularly limited, and may be any filler capable of exhibiting desired properties to be imparted to the resulting composite sheet. For example, when the composite sheet is used as a thermally conductive sheet, a thermally conductive filler can be used as the filler.

Examples of thermally conductive fillers include, but are not limited to, alumina particles, zinc oxide particles, boron nitride particles, aluminum nitride particles, silicon nitride particles, silicon carbide particles, magnesium oxide particles, and particulate carbon materials (e.g. , artificial graphite, flake graphite, exfoliated graphite, natural graphite, acid-treated graphite, expanded graphite, expanded graphite, carbon black, etc.), as well as carbon nanotubes, vapor-grown carbon fibers, organic fibers fibrous materials such as carbon fibers obtained by carbonizing and cut products thereof. Among them, thermally conductive fillers include scaly particle materials such as boron nitride particles, artificial graphite, scaly graphite, expansive graphite, and expanded graphite; and carbon nanotubes (hereinafter sometimes referred to as "CNT" It is preferable to use at least one selected from the group consisting of fibrous carbon nanomaterials such as .), more preferably scaly particle materials, anisotropic graphite such as scaly graphite and expanded graphite is more preferably used, and expanded graphite is particularly preferably used. The thermal conductivity of the composite sheet can be enhanced by using these thermally conductive fillers.
In addition, fillers, such as a thermally conductive filler, may be used individually by 1 type, and may use 2 or more types together.

Here, when the filler used for the preparation of the powder composition is a particulate material such as a particulate carbon material, the volume average particle diameter of the particulate material increases as the content of the filler in the composite sheet increases. Even when the thickness is 10 μm or more, it is preferably 10 μm or more, and 30 μm or more, from the viewpoint of making the composite sheet excellent in various properties (thermal conductivity, etc.) while ensuring sufficient flexibility of the composite sheet. is more preferably 100 μm or less, and more preferably 80 μm or less.

The content of the filler in the powder composition is not particularly limited, and is preferably 5% by mass or more, more preferably 10% by mass or more, and preferably 50% by mass or less. , 45% by mass or less. When the proportion of the filler in the powder composition is 5% by mass or more, the obtained composite sheet can sufficiently exhibit various properties such as thermal conductivity. On the other hand, if the ratio of the filler in the powder composition is 50% by mass or less, the moldability can be improved when the powder composition is rolled into a sheet.

Moreover, the content ratio of the resin and the filler in the powder composition is not particularly limited. For example, the powder composition preferably contains 10 parts by mass or more of the filler per 100 parts by mass of the resin, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, and 90 parts by mass or less. It is preferably contained, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less. When the content of the filler in the powder composition is 10 parts by mass or more per 100 parts by mass of the resin, the obtained composite sheet can sufficiently exhibit various properties such as thermal conductivity. On the other hand, if the content of the filler in the powder composition is 90 parts by mass or less per 100 parts by mass of the resin, it is possible to improve moldability when rolling the powder composition into a sheet.

<Other ingredients>
Other components that may optionally be contained in the heat conductive sheet are not particularly limited, and include, for example, flame retardants, plasticizers, toughness improvers, moisture absorbers, adhesion improvers, wettability improvers, and ion trap agents. Additives such as In addition, another component may be used individually by 1 type, and may use 2 or more types together.

<Properties of powder composition>
Here, in the powder composition, it is preferable that the above-mentioned resin and filler are physically integrated to form a composite and form particles. That is, the powder composition preferably contains composite particles in which a resin and a filler are composited. By using a powder composition containing composite particles in which a resin and a filler are combined, it is possible to suppress powder scattering and powder drop-off during production of a composite sheet.

Here, when the powder composition contains composite particles in which a resin and a filler are combined, the powder composition may contain components other than the composite particles. Examples of components other than the composite particles include resins, fillers, and other components described above that are not included in the composite particles in the manufacturing process of the powder composition containing the composite particles and exist separately from the composite particles. . However, the content of components other than the composite particles in the powder composition used in the production method of the present invention is preferably 10% by mass or less, more preferably 5% by mass or less, and 1% by mass or less. More preferably, it is 0% by mass or less (that is, the powder composition consists only of composite particles).

<Method for preparing powder composition>
The method of preparing the powder composition containing resin and filler is not particularly limited. For example, a powder composition containing composite particles in which a resin and a filler are combined includes a step of combining the resin and the filler to obtain a composite mixture (compositing step), and pulverizing the composite mixture obtained in the compounding step. It can be manufactured through a step (pulverization step).

<<Complex Process>>
In the compounding step, a compound mixture is obtained by compounding the resin, filler, and optionally other components. The method of compositing is not particularly limited, but a method of kneading the above components using a known kneading device such as a kneader is preferred. Kneading may be performed in the presence of a solvent such as ethyl acetate or methyl ethyl ketone. Moreover, the kneading temperature can be, for example, 5° C. or higher and 200° C. or lower.

<<Pulverization process>>
In the pulverization step, the composite mixture obtained in the composite step is pulverized to obtain a powder composition containing composite particles. A method for pulverizing the composite mixture is not particularly limited, and a known pulverizing apparatus can be used.
As for the pulverization conditions in the pulverization step, the pulverization device, the pulverization strength, etc. may be appropriately selected or adjusted according to the desired particle size of the composite particles obtained after pulverization.

(Base film)
The base film is not particularly limited as long as a composite sheet can be formed thereon, and films made of known materials can be used. As the base film, a resin film is preferable, and a polyethylene terephthalate (PET) film is more preferable, from the viewpoints of excellent flexibility, bendability, etc. and easy transportation.
The thickness of the base film is not particularly limited, but can be, for example, 10 μm or more and 150 μm or less. Further, the base film may be subjected to a known release treatment on its surface.

(adhesive sheet)
The material of the pressure-sensitive adhesive sheet is not particularly limited as long as it can exert a stronger adhesive force to the base film after rolling than the composite sheet obtained by molding the powder composition. However, the pressure-sensitive adhesive sheet is preferably a sheet containing resin (resin sheet) from the viewpoint of easily obtaining good adhesive strength and compressibility, and from the viewpoint of preventing contamination of the composite sheet with the powder described above. More preferably, it is a resin sheet obtained using the same or similar materials as the composition (resin, filler, and other components described above). For example, when forming a composite sheet using a powder composition containing a fluororesin as a resin and graphite as a filler, a resin sheet made of a fluororesin or a resin sheet made of a fluororesin and graphite can be used as the pressure-sensitive adhesive sheet. It is preferable to use

<Compression rate>
Here, the pressure-sensitive adhesive sheet before being subjected to rolling, which will be described later, preferably has a compressibility of 5% or more, more preferably 10% or more, and more preferably 20% or more, as calculated by the above formula (1). 25% or more is particularly preferable. When the compressibility is 5% or more, the pressure-sensitive adhesive sheet can be easily deformed by rolling, and can adhere well to the base film. Therefore, it is possible to further suppress the separation of the composite sheet, which is conveyed while being bonded to the pressure-sensitive adhesive sheet, from the base film. Although the upper limit of the compressibility of the base film is not particularly limited, it can be set to, for example, 90% or less from the viewpoint of ensuring handleability.

<Adhesive strength to base film>
The adhesive strength of the pressure-sensitive adhesive sheet to the substrate film after rolling, which will be described later, is not particularly limited as long as it is greater than the adhesive strength of the composite sheet obtained by molding the powder composition to the substrate film, as described above. is preferably 0.3 N or more, more preferably 0.5 N or more, still more preferably 1.5 N or more, particularly preferably 2 N or more, and preferably 10 N or less. , 8N or less, more preferably 7N or less. If the adhesive strength of the pressure-sensitive adhesive sheet to the base film is 0.3 N or more, it is possible to further suppress the separation of the composite sheet, which is conveyed while being bonded to the pressure-sensitive adhesive sheet, from the base film. On the other hand, if the adhesive force of the adhesive sheet to the base film is 10 N or less, the adhesive sheet is not on the base film side but on the opposing rolling roll side (rolling roll surface, or when using a cover film, the cover film surface ) can be sufficiently suppressed.
The adhesive strength of the pressure-sensitive adhesive sheet to the base film can be changed by changing the material used to produce the pressure-sensitive adhesive sheet, the compression rate of the pressure-sensitive adhesive sheet, the type of base film, the release treatment conditions, and the rolling conditions. can be adjusted.

<Thickness>
Moreover, the thickness of the pressure-sensitive adhesive sheet is preferably larger than the width of the gap between the pair of rolling rolls before passing through the gap between the pair of rolling rolls used for rolling (that is, before rolling). If the thickness of the pressure-sensitive adhesive sheet before rolling is larger than the gap width between the pair of rolling rolls, the pressure-sensitive adhesive sheet is sufficiently compressed during rolling, and can adhere well to the base film. Therefore, it is possible to further suppress the separation of the composite sheet, which is conveyed while being bonded to the pressure-sensitive adhesive sheet, from the base film. Specifically, the thickness of the adhesive sheet is preferably 500 μm or more, more preferably 800 μm or more, still more preferably 1000 μm or more, preferably 2500 μm or less, and preferably 2000 μm or less. More preferably, it is 1500 μm or less.
The shape of the pressure-sensitive adhesive sheet in a plan view is not particularly limited, and may be, for example, an arbitrary shape such as a substantially square shape or a substantially rectangular shape. The width and length in the direction of conveyance of the pressure-sensitive adhesive sheet can be appropriately set according to the size of the rolling rolls (roll diameter, roll width, etc.) and the desired size of the composite sheet.

(rolling)
The powder composition is conveyed on the substrate film described above and passed through a gap between a pair of rolling rolls to roll the powder composition. As described above, when rolling the powder composition, a cover film that follows the rotation of the roll while being in contact with the surface of the roll that is not in contact with the base film of the two rolls is used to roll the powder composition. It is preferred to roll the article between the base film and the cover film. By performing rolling using the cover film in this way, it is possible to sufficiently suppress the phenomenon in which the pressure-sensitive adhesive sheet unintentionally follows the opposite rolling roll side instead of the base film side.

A film made of a known material can be used as the cover film. As the cover film, a resin film is preferable, and a polyethylene terephthalate (PET) film is more preferable, from the viewpoints of excellent flexibility, bendability, etc. and easy transportation. The thickness of the cover film is not particularly limited, but can be, for example, 10 μm or more and 150 μm or less. Moreover, it is preferable that the surface of the substrate film is subjected to a known release treatment.

Here, the gap width between the pair of rolling rolls used for rolling can be appropriately set according to the desired thickness of the composite sheet. The gap width between the pair of rolling rolls can be, for example, 100 μm or more and 3000 μm or less.
In the present invention, the width of the gap between the pair of rolling rolls means the surface of the rolling rolls facing the surface of the base film at the point where the two rolling rolls are closest to each other (if a cover film is used, the surface of the cover film ) and can be measured using, for example, a feeler gauge.

The roll temperature during rolling is not particularly limited, but is preferably 50° C. or higher, more preferably 60° C. or higher, preferably 130° C. or lower, and more preferably 120° C. or lower. preferable. If the roll temperature is 50° C. or higher, the pressure-sensitive adhesive sheet and the composite sheet can be well adhered to the base film. Therefore, peeling of the composite sheet from the base film during transportation can be further suppressed. On the other hand, if the roll temperature is 130° C. or less, thermal deformation of the base film and the cover film can be suppressed, and good workability can be ensured.

(composite sheet)
A composite sheet is formed on the base film through the rolling described above. Here, the composite sheet is positioned on the upstream side in the conveying direction of the adhesive sheet on the base film, and is formed continuously with the adhesive sheet. The formed composite sheet can be used for various purposes by separating the pressure-sensitive adhesive sheet as necessary.

Here, the thickness of the composite sheet is not particularly limited and may be appropriately determined according to the application of the composite sheet. The thickness of the composite sheet may be, for example, 100 μm or more, 500 μm or more, 700 μm or more, 800 μm or more, 900 μm or more, or 1200 μm or more. can be 2000 μm or less, and can be 1400 μm or less.
Here, the thicker the composite sheet, the more likely it is to be peeled off from the base film during transportation, because the composite sheet bends more when passing through the feeding rolls than the thinner composite sheet. However, according to the method for producing a composite sheet of the present invention, even when the thickness of the obtained composite sheet is increased (for example, 800 μm or more), the composite sheet is sufficiently peeled from the base film during transportation. can be suppressed.

In addition, when the filler contained in the composite sheet is a particulate material such as a particulate carbon material, the volume average particle diameter of the particulate material is However, the thickness is preferably 10 μm or more, and preferably 30 μm or more, from the viewpoint of ensuring sufficient flexibility of the composite sheet and improving various properties (such as thermal conductivity) of the composite sheet. is more preferably 100 μm or less, and more preferably 80 μm or less.

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified.
Then, in Examples and Comparative Examples, measurement or evaluation was performed according to the following methods.

<Adhesive strength>
<<Adhesive sheet>>
A circular test piece (laminate of base film and pressure-sensitive adhesive sheet) with a diameter of 10 mm was cut out from the pressure-sensitive adhesive sheet portion of the composite sheet and pressure-sensitive adhesive sheet that were joined on the base film. Using a probe tack tester (manufactured by Lesca Co., Ltd., product name "TAC1000"), the probe is pressed against the adhesive sheet side of the test piece at 8 N for 10 seconds and lifted, and the force when the adhesive sheet is peeled from the base film ( N) was measured and taken as adhesive strength.
<< Composite sheet >>
A circular test piece having a diameter of 10 mm (laminated body of the base film and the composite sheet) was cut out from the composite sheet portion of the composite sheet and the pressure-sensitive adhesive sheet which were joined on the base film. Using a probe tack tester (manufactured by Lesca Co., Ltd., product name "TAC1000"), the probe was pressed against the composite sheet side of the test piece at 8 N for 10 seconds and pulled up, and the force when the composite sheet was peeled off from the base film ( N) was measured and taken as adhesive strength.
<Compression rate>
The compressibility of the adhesive sheet was measured using a thermal resistance tester (manufactured by Hitachi Technology and Service Co., Ltd., product name "resin material thermal resistance measuring device").
Specifically, first, the pressure-sensitive adhesive sheet was cut into a 1 cm-square approximately square to obtain a test piece, and the thickness T ₀ was measured. Next, the thickness T _P of the test piece was measured under a pressure of 0.2 MPa at a test piece temperature of 50°C. Then, the following formula (1)
Compression ratio={1-(T _P /T ₀ )}×100(%) (1)
was used to calculate the compression rate.
<Volume average particle size of particulate material>
1 g of the composite sheet was placed in methyl ethyl ketone as a solvent to dissolve the resin and the like in the composite sheet, thereby obtaining a suspension in which the particulate material (expanded graphite) contained in the composite sheet was separated and dispersed. . Next, the particle size of the particulate material contained in the suspension was measured using a laser diffraction/scattering particle size distribution analyzer (manufactured by Horiba Ltd., model "LA960"). Then, a particle size distribution curve was prepared with the obtained particle diameter as the horizontal axis and the volume-converted particle frequency as the vertical axis. In the particle size distribution curve, the particle diameter (D50) at which the cumulative volume calculated from the smaller diameter side becomes 50% was obtained and used as the value of the volume average particle diameter of the particulate material.
<Thickness>
A film thickness gauge (manufactured by Mitutoyo Co., Ltd., product name “Digimatic Indicator ID-C112XBS”) was used to determine the thickness of the adhesive sheet and composite sheet. Specifically, the average value (μm) of the values measured at arbitrary five points on the surfaces of the pressure-sensitive adhesive sheet and the composite sheet was taken as their thickness.
<Suppression of peeling from the base film>
Suppression of peeling of the composite sheet from the base film is evaluated by visually checking how much the pressure-sensitive adhesive sheet, which precedes the composite sheet and is conveyed after bonding, has peeled from the base film, and is evaluated according to the following criteria. did. If the evaluation is A to B, it can be said that peeling of the composite sheet following the pressure-sensitive adhesive sheet from the base film can be sufficiently suppressed.
A: The pressure-sensitive adhesive sheet is not peeled from the base film at all, or more than 0 area% and less than 10 area% of the main surface of the pressure-sensitive adhesive sheet (surface on the side that adheres to or approaches the base film) is peeled from the base film. are doing.
B; 10 area % or more and 60 area % or less of the main surface of the pressure-sensitive adhesive sheet is separated from the base film.
C: More than 60 area % of the main surface of the pressure-sensitive adhesive sheet is peeled off from the base film.
<Suppression of sticking to cover film>
After rolling, it was visually confirmed whether at least a part of the pressure-sensitive adhesive sheet adhered to the cover film, and evaluated according to the following criteria.
A: Part of the adhesive sheet is not attached to the surface of the cover film.
B: Part of the adhesive sheet adheres to the surface of the cover film.

(Production Example 1 Preparation of powder composition 1)
70 parts of a thermoplastic fluororesin that is liquid under normal temperature and pressure (manufactured by Daikin Industries, Ltd., product name "Dai-El G-101") and a thermoplastic fluororesin that is solid under normal temperature and pressure (3M Japan Co., Ltd., product name " Dyneon FC-2211”, Mooney viscosity: ML ₁₊₄ (100° C.)) 30 parts, and expanded graphite as a filler (manufactured by Ito Graphite Industry Co., Ltd., product name “EC100”, volume average particle size: 190 μm) 50 parts were stirred and mixed at 150° C. for 20 minutes using a pressure kneader (manufactured by Nihon Spindle) to obtain a composite mixture.
The obtained composite mixture was put into a pulverizer and pulverized for 10 seconds to obtain a powder composition 1 composed of composite particles.

(Production Example 2 Preparation of powder composition 2)
As a filler, instead of expanded graphite (product name “EC100”), expanded graphite (manufactured by Ito Graphite Industry Co., Ltd., product name “EC300”, volume average particle size: 50 μm) 90 parts was used. A powder composition 2 was obtained in the same manner as in Production Example 1.

(Production Example 3 Preparation of powder composition 3)
Powder composition 3 was prepared in the same manner as in Production Example 1, except that the thermoplastic fluororesin that was solid at room temperature and pressure was not used, and the amount of the thermoplastic fluororesin that was liquid at room temperature and pressure was changed from 70 parts to 100 parts. got

(Production Example 4 Preparation of powder composition 4)
A powder composition 4 was obtained in the same manner as in Production Example 3, except that the amount of expanded graphite was changed from 50 parts to 40 parts.

(Production Example 5 Preparation of powder composition 5)
A powder composition 5 was obtained in the same manner as in Production Example 2, except that the amount of expanded graphite was changed from 90 parts to 120 parts.

(Example 1)
<Production of adhesive sheet>
A PET film (base film) having a thickness of 100 μm with a release treatment and a release treatment different from the base film were applied to a pair of rolling rolls of a heating roll laminator (manufactured by Hirano Giken Kogyo Co., Ltd.). The powder composition 1 was continuously supplied in a state in which a PET film (cover film) having a thickness of 75 μm was laid (adhered) on the surface of each rolling roll, and the powder composition 1 was placed between the base film and the cover film. By conveying the powder composition 1, it was allowed to pass through the gap between the rolling rolls to obtain a long sheet (thickness: 1300 µm). A pressure-sensitive adhesive sheet of 150 mm×50 mm (thickness: 1300 μm) was cut out from the resulting sheet.
The rolling conditions are as follows.
Gap width: 1100 μm
Roll temperature: 100°C
Roll line pressure: 0.35t (ton)/cm
Roll speed: 1 m/min The compressibility and thickness of the obtained adhesive sheet were measured. Table 1 shows the results.
<Production of composite sheet>
A PET film (base film) having a thickness of 100 μm with a release treatment and a release treatment different from the base film were applied to a pair of rolling rolls of a heating roll laminator (manufactured by Hirano Giken Kogyo Co., Ltd.). The pressure-sensitive adhesive sheet was supplied between the base film and the cover film in a state in which a PET film (cover film) having a thickness of 75 μm was laid on (adhered to) the surface of each rolling roll. The powder composition 2 prepared in Production Example 2 was supplied at a supply rate of 250 g/min from the back of the adhesive sheet in the conveying direction, and the adhesive sheet and the powder composition were continuously placed in this order across the gap between the rolling rolls. A composite sheet was obtained in a state in which the adhesive sheet was bonded to the downstream end portion in the conveying direction.
The rolling conditions are as follows.
Gap width: 650 μm
Roll temperature: 100°C
Roll line pressure: 0.35t (ton)/cm
Roll speed: 1 m/min After the rolling, the adhesive force to the substrate film was measured for each of the pressure-sensitive adhesive sheet and the composite sheet. Moreover, during the rolling, the suppression of peeling from the base film and the suppression of adhesion to the cover film were evaluated. Furthermore, the thickness, the content ratio of the filler, and the volume average particle size of the obtained composite sheet were measured. Table 1 shows the results. In addition, the content ratio of the filler is obtained by dividing the mass of the filler contained in the composite sheet by the density to obtain the volume occupied by the filler, and the ratio of the filler to 100% by volume of the composite sheet ( volume %).

(Examples 2-4)
In the preparation of the pressure-sensitive adhesive sheet, powder composition 2 (Example 2), powder composition 3 (Example 3), and powder composition (Example 4) were used instead of powder composition 1. Except for this, a pressure-sensitive adhesive sheet and a composite sheet were produced in the same manner as in Example 1, and various measurements and evaluations were performed. Table 1 shows the results.

(Example 5)
A pressure-sensitive adhesive sheet and a composite sheet were produced in the same manner as in Example 1, except that the gap width was changed from 650 μm to 1100 μm, and various measurements and evaluations were performed. Table 1 shows the results.

(Comparative example 1)
A composite sheet was produced in the same manner as in Example 1, except that no adhesive sheet was produced and no adhesive sheet was used in producing the composite sheet, and various measurements and evaluations were performed. Table 1 shows the results.

(Comparative example 2)
A pressure-sensitive adhesive sheet and a composite sheet were prepared in the same manner as in Example 1, except that powder composition 5 was used instead of powder composition 1 in preparing the pressure-sensitive adhesive sheet, and various measurements and evaluations were performed. Table 1 shows the results.

From Table 1, it can be seen that in Examples 1 to 5, peeling of the composite sheet from the base film during transportation can be sufficiently suppressed.
In addition, in Example 2, the powder composition 2 is used for both the preparation of the pressure-sensitive adhesive sheet and the composite sheet. However, there is a difference between the pressure-sensitive adhesive sheet and the composite sheet in the adhesive strength to the base film after rolling, and the pressure-sensitive adhesive sheet is larger. This is presumably because the pressure-sensitive adhesive sheet that has been preformed before rolling can more efficiently reflect the pinching pressure of roll rolling on the adhesive strength.

According to the manufacturing method of the composite sheet of the present invention, even when the content of the filler in the composite sheet is increased, the separation of the composite sheet from the base film during transportation can be suppressed.

1 Base film 2 Winding bodies 31, 32 Rolling roll 4 Adhesive sheet 5 Powder feeder 6 Powder composition 7 Composite sheet 8 Cover film 9 Feed roll 10 Winding machine F Conveying direction

Claims (7)

A base film and a powder composition containing a resin and a filler supplied on the base film are conveyed, and the powder composition is passed through a gap between a pair of rolling rolls to roll the powder composition. , a method for producing a composite sheet, comprising the step of forming a composite sheet having a filler content of 30% by volume or more on the base film,
The rolling is arranged on the same surface as the supply surface of the powder composition on the base film and on the downstream side of the powder composition in the conveying direction of the base film. The composite sheet is formed in a state of being joined to the adhesive sheet by continuously passing the adhesive sheet and the adhesive sheet through the gap,
A method for producing a composite sheet, wherein the pressure-sensitive adhesive sheet has a higher adhesive strength to the base film than the composite sheet to the base film after the rolling. 2. The method for producing a composite sheet according to claim 1, wherein said filler contained in said composite sheet is a particulate material having a volume average particle size of 100 [mu]m or less. The method for producing a composite sheet according to claim 1 or 2, wherein the filler is a scale-like particulate material. When the thickness of the pressure-sensitive adhesive sheet under pressure in the thickness direction under conditions of 0.2 MPa and 50° C. is T _P and the thickness of the pressure-sensitive adhesive sheet before pressure is T ₀ , the following formula (1):
Compression ratio={1-(T _P /T ₀ )}×100(%) (1)
The method for producing a composite sheet according to any one of claims 1 to 3, wherein the pressure-sensitive adhesive sheet has a compressibility of 5% or more before the rolling, calculated by: The method for producing a composite sheet according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive sheet has an adhesive strength of 0.3 N or more and 10 N or less to the base film after the rolling. The method for producing a composite sheet according to any one of claims 1 to 5, wherein the composite sheet has a thickness of 800 µm or more. The method for producing a composite sheet according to any one of claims 1 to 6, wherein the thickness of said pressure-sensitive adhesive sheet before said rolling is greater than the width of said gap.

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