JP5792904B2 - Release film - Google Patents

Description

The present invention relates to a release film that is excellent in releasability, can suppress resin flow even under high-temperature molding conditions, and can suppress defects in product appearance.

In the manufacture of semiconductor products, a semiconductor mold process is performed in which a semiconductor chip is sealed with a resin using a mold to obtain a molded product. In this semiconductor molding process, by performing resin molding in a state where the inner surface of the mold is covered with a release film, productivity is improved and contamination of the mold by the resin is prevented. Conventionally, fluorine-based films have been generally used as mold release films for semiconductor molding processes, but there are cost problems, wrinkles due to heat shrinkage, and environmental aspects that incineration treatment cannot be performed due to generation of fluorine-based gas at the time of disposal. Thus, there is a need for a new release film that does not use a fluorine-based film as a substrate.

Patent Document 1 describes a release sheet for a semiconductor package that includes at least two layers of a release layer (A layer) and a layer that bears heat resistance against heating during molding (B layer), and the B layer is unstretched. Of nylon 6 resin. However, nylon 6 resin has a drawback that it is not suitable for long-term storage because of its high hygroscopicity.

Examples of the resin having a relatively low hygroscopic property include a polyester resin. Patent Document 2 describes a laminated film in which a film made of a fluororesin is laminated on at least one surface of a base film made of a stretched polyester resin film.
However, when a release film having a stretched polyester resin film as a support layer as described in Patent Document 2 is used, when a predetermined amount of resin is injected under a high temperature condition where molding is performed, the resin is outside the mold. It sometimes overflowed.

JP 2004-79567 A JP 2006-49850 A

An object of the present invention is to provide a release film that is excellent in releasability, suppresses resin flow even under high-temperature molding conditions, and can suppress defects in product appearance.

The present invention is a release film having a single layer structure or a multilayer structure support layer having at least one layer containing a polybutylene terephthalate resin, and a release layer.
The present invention is described in detail below.

In order to suppress the overflow of the resin to the outside of the mold (hereinafter, also simply referred to as “resin flow”), the inventor has improved the flexibility of the release film under high-temperature molding conditions, We studied to improve the follow-up performance for As a result, in a release film having a support layer and a release layer, a single layer structure or a multilayer structure having at least one layer containing polybutylene terephthalate resin (PBT) (hereinafter also referred to as “PBT layer”). By using this support layer, it was found that not only the mold releasability was excellent, but also the resin flow could be suppressed even under high temperature molding conditions, and the present invention was completed.

The release film of the present invention has a support layer having a single layer structure or a multilayer structure having at least one PBT layer.
Since the support layer has a PBT layer, the release film of the present invention is highly flexible under high-temperature molding conditions and can exhibit sufficient followability to the mold. Can be suppressed, and defects in the appearance of the product can be suppressed. In addition, by using the PBT layer, the release film of the present invention is economically advantageous because the environmental load during incineration treatment is reduced as compared with the case of using a fluorine-based film. Furthermore, since PBT is a resin having a small amount of low molecular weight components, contamination of a mold or the like due to bleed out of the low molecular weight components accompanying hot pressing can be suppressed.

In this specification, the polybutylene terephthalate resin (PBT) is a polybutylene terephthalate obtained by a polycondensation reaction between 1,4-butanediol (diol component) and terephthalic acid or dimethyl terephthalate (acid component). It may be a modified polybutylene terephthalate obtained by adding a comonomer to the diol component and / or the acid component, respectively, and performing a polycondensation reaction.
Examples of the comonomer of the diol component include ethylene glycol, propylene glycol, tetramethylene glycol, and cyclohexanedimethanol. Examples of the acid component comonomer include isophthalic acid, adipic acid, and sebacic acid. The comonomer of the diol component and the comonomer of the acid component may be used alone or in combination of two or more.
The polybutylene terephthalate resin (PBT) can also be a PBT elastomer (copolymer of hard segment and soft segment) such as a copolymer of polybutylene terephthalate and polyalkylene glycol.
The PBT layer may contain each of the polybutylene terephthalate, modified polybutylene terephthalate, and PBT elastomer alone, or may contain two or more of these in combination.

The PBT preferably has a melting point of 200 ° C. or higher measured using a differential scanning calorimeter. By using a polybutylene terephthalate resin having a melting point of 200 ° C. or more, it is not melted or broken under normal hot press conditions of less than 200 ° C., and excellent release properties can be exhibited. The melting point is more preferably 220 ° C. or higher.
An example of the differential scanning calorimeter is DSC 2920 (manufactured by TA Instruments).

The minimum with preferable content of PBT in the said PBT layer is 60 weight%, More preferably, it is 70 weight%, More preferably, it is 80 weight%. When the PBT layer contains PBT in an amount of 60% by weight or more, the excellent effect of the present invention that suppresses the flow of the resin even under high temperature molding conditions and suppresses the defective appearance of the product can be surely exhibited. The upper limit of the content of the polybutylene terephthalate resin is not particularly limited, and 100% by weight may be a polybutylene terephthalate resin.

The PBT layer may contain a thermoplastic resin or a rubber component other than the polybutylene terephthalate resin as long as the effects of the present invention are not impaired.
The thermoplastic resin is not particularly limited, and examples thereof include polyolefin, modified polyolefin, polystyrene, polyvinyl chloride, polyamide, polycarbonate, polysulfone, and polyester.
The rubber component is not particularly limited. For example, natural rubber, styrene-butadiene copolymer, polybutadiene, polyisoprene, acrylonitrile-butadiene copolymer, ethylene-propylene copolymer (EPM, EPDM), polychloroprene, butyl rubber. , Acrylic rubber, silicon rubber, urethane rubber and the like.

The PBT layer may contain additives such as stabilizers, fibers, inorganic fillers, flame retardants, ultraviolet absorbers, antistatic agents, inorganic substances, higher fatty acid salts and the like as long as the effects of the present invention are not impaired. .

The said stabilizer is not specifically limited, For example, a hindered phenolic antioxidant, a heat stabilizer, etc. are mentioned. The hindered phenol antioxidant is not particularly limited. For example, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxybenzyl) benzene, 3 , 9-bis {2- [3- (3-t-butyl-4-hydroxy-5-methylphenyl) -propionyloxy] -1,1-dimethylethyl} -2,4,8,10-tetraoxa Examples include spiro [5,5] undecane. The heat stabilizer is not particularly limited, and examples thereof include tris (2,4-di-t-butylphenyl) phosphite, trilauryl phosphite, 2-t-butyl-α- (3-t-butyl-4- Hydroxyphenyl) -p-cumenylbis (p-nonylphenyl) phosphite, dimyristyl 3,3′-thiodipropionate, distearyl 3,3′-thiodipropionate, pentaerythryltetrakis (3-laurylthiopropio) Nate), ditridecyl 3,3′-thiodipropionate and the like.

The fiber may be an inorganic fiber or an organic fiber. The inorganic fiber is not particularly limited, and examples thereof include glass fiber, carbon fiber, boron fiber, silicon carbide fiber, alumina fiber, amorphous fiber, and silicon-titanium-carbon fiber. The said organic fiber is not specifically limited, For example, an aramid fiber etc. are mentioned.

The inorganic filler is not particularly limited, and examples thereof include calcium carbonate, titanium oxide, mica and talc.
The flame retardant is not particularly limited, and examples thereof include hexabromocyclododecane, tris- (2,3-dichloropropyl) phosphate, pentabromophenyl allyl ether, and the like.
The ultraviolet absorber is not particularly limited. For example, pt-butylphenyl salicylate, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2′-carboxybenzophenone, 2,4,5-tri And hydroxybutyrophenone.
The antistatic agent is not particularly limited, and examples thereof include N, N-bis (hydroxyethyl) alkylamine, alkylallyl sulfonate, and alkyl sulfonate.
The inorganic material is not particularly limited, and examples thereof include barium sulfate, alumina, and silicon oxide.
The higher fatty acid salt is not particularly limited, and examples thereof include sodium stearate, barium stearate, and sodium palmitate.

When the release film support layer of the present invention is a film having a plurality of layers, it may have an intermediate layer. In this case, the layer containing the polybutylene terephthalate resin is preferably in the outermost layer on the side opposite to the release layer.
The intermediate layer preferably contains a polyolefin resin.
Examples of the polyolefin resin include polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, ethylene-methyl methacrylate copolymer, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene- An acrylic acid copolymer etc. are mentioned. These polyethylene resins may be used alone or in combination of two or more.
The said intermediate | middle layer may contain additives, such as a fiber, an inorganic filler, a flame retardant, a ultraviolet absorber, an antistatic agent, an inorganic substance, and a higher fatty acid salt similarly to the said surface layer.

The support layer may be a non-stretched resin layer or a stretched resin layer. However, since the support layer is particularly flexible under high-temperature molding conditions and has high followability to the mold, the non-stretched resin layer may be used. A layer is preferred. When the support layer is a stretched resin layer, the stretch ratio is preferably 3 times or less, more preferably 2 times or less, and further preferably 1.5 times or less.
In the present specification, the term “non-stretched resin layer” means that the raw sheet extruded from the die by the extruder is not subjected to a heat stretching process by a stretching device.

The release film preferably has a satin finish on one side or both sides. In addition, when one side is satin-finished, it is preferable that the mold release layer side is satin-finished. In this specification, the satin finish means forming fine irregularities on the surface of the release film.
Since one side or both sides of the release film has been satin-finished, the satin-like shape is shaped on the surface of the molded product, making it difficult to see the resin flow pattern (flow mark), and deteriorating the appearance of the molded product. Can be suppressed.
In addition, since the thickness of a release layer is very thin, as for the said release film, the single side | surface or both surfaces of a support layer may be satin processed. Even when the release layer side of the support layer is satin-finished, fine irregularities can be formed in the same manner as when the release layer itself is satin-finished.

The release film preferably has a ten-point average roughness Rz of 3.0 or more on the textured surface. If the ten-point average roughness Rz is less than 3.0, the appearance of the molded product may be deteriorated due to the resin flow pattern (flow mark). The ten-point average roughness Rz is more preferably 5.0 or more.
The upper limit of the ten-point average roughness Rz is not particularly limited, but is preferably 15.0 or less. When the ten-point average roughness Rz exceeds 15.0, the release property of the release film may be deteriorated. The ten-point average roughness Rz is more preferably 15.0 or less.

In the present specification, it is possible to confirm that the matte finish has been processed and that the ten-point average roughness of the matte finish surface is measured using a surface roughness meter. Note that the ten-point average roughness of the surface means that the altitude of the peak from the highest peak to the fifth highest in the reference length L is Y _p1 , Y _p2 , Y _p3 , Y _p4 and Y _p5 , and the deepest valley bottom. Means the value (unit: μm) obtained by the following formula (1), where Y _v1 , Y _v2 , Y _v3 , Y _v4 and Y _v5 are the elevations of the valley bottom from the depth to the fifth depth, respectively. The larger the value, the rougher the surface, and the smaller the value, the smoother the surface as a whole. Examples of the surface roughness meter include Permeter M1 (manufactured by Mahr).

Although the method of carrying out a satin finish processing to the said release film is not specifically limited, The method of processing by heating and pressurizing the formed release film with the roll which has an embossed shape is preferable.

Although the thickness of the said support layer is not specifically limited, A preferable minimum is 10 micrometers and a preferable upper limit is 200 micrometers. When the thickness of the support layer is less than 10 μm, the strength is impaired, and the release film may be broken during hot pressing or peeling. When the thickness of the support layer exceeds 200 μm, the flexibility of the release film under high-temperature molding conditions is lowered, the followability to the mold is lowered, and the resin flow may not be suppressed. A more preferable lower limit of the thickness of the support layer is 30 μm, and a more preferable upper limit is 100 μm.

The release film of the present invention has a release layer.
The release layer is not particularly limited as long as it can exhibit releasability, but a layer formed by applying a release agent and thermosetting or ultraviolet curing as necessary is preferable. Examples of the release agent include thermosetting release agents such as fluorine and amino alkyd, and ultraviolet curable release agents such as urethane acrylate. Among these, a fluorine-based mold release agent is preferable because it exhibits particularly excellent mold release properties with respect to the mold resin.

The fluorine-based mold release agent is not particularly limited. For example, MR W-6823-AL, MR W-6833-AL, MR W-684-AL, MR W-6881-AL, MR F-6441-AL, MR F-6711-AL, MR F-6758-AL, MR F-6811-AL, MR EF-6521-AL, MR K-6714-AL, MR X-6712-AL (manufactured by AGC Sey Chemical) F-release 600, F-release 360, F-release 390, F-release 1200, F-release 1300, F-release 1900, F-release 351, F-release 380, F-release 450, F-release 11F, F-release 50GA, F-release 20, F-release 22, F-release 23, F-release 26, F-release 800, F-release 410, Release 430, FRX-AS24, Release 44, Release PH206, Release PH300, FRX-AZ15 (above, manufactured by Neos), GW-200, GW-201, GW-250, GW-251, GW-280 , GF-500, GF-501, GF-550, GF-350, MS-600, GA-3000, GA-7500, GA-7550, GA-7550B, GA-7550C, FB-961, FB-962 (or above) , Manufactured by Daikin Industries, Ltd.).
The amino alkyd release agent is not limited, and examples thereof include Tesfine 303, Tesfine 305, Tesfine 314, Tesfine 319, and TA31-209E (manufactured by Hitachi Chemical Co., Ltd.).
The urethane acrylate release agent is not particularly limited, and examples thereof include TA37-400A, TA37-400B, TA37-400C, TA37-401A, TA37-401B, TA37-401C (above, manufactured by Hitachi Chemical Co., Ltd.). .

The thickness of the release layer is not particularly limited, but a preferable lower limit is 0.1 μm and a preferable upper limit is 10 μm. When the thickness of the release layer is less than 0.1 μm, the release property of the release layer may not be sufficiently exhibited. When the thickness of the release layer exceeds 10 μm, the cost becomes high, and problems such as poor drying in the coating process may occur depending on the type of the release agent. A more preferable lower limit of the thickness of the release layer is 0.3 μm, and a more preferable upper limit is 5 μm.

In the release film of the present invention, the preferable lower limit of the elastic modulus at 170 ° C. of the release film is 20 MPa, and the preferable upper limit is 150 MPa. When the release film has an elastic modulus at 170 ° C. of less than 20 MPa, wrinkles occur in the release film during adsorption to the mold or during hot pressing, and the wrinkles are transferred to a molded product or released during hot pressing. The film may be torn. When the elastic modulus at 170 ° C. of the release film exceeds 150 MPa, the flexibility of the release film under high-temperature molding conditions is lowered, the followability to the mold is lowered, and the resin flow may not be suppressed. The more preferable lower limit of the elastic modulus at 170 ° C. of the release film is 40 MPa, and the more preferable upper limit is 70 MPa.
In this specification, the elastic modulus at 170 ° C. can be measured by using a universal testing machine (for example, AUTOGRAPH AGS-X manufactured by Shimadzu Corporation).

The method for producing the release film of the present invention is not particularly limited, but a release agent is applied to the formed support layer, heat-cured or UV-cured as necessary, and then heated with a roll having an embossed shape. -A method of processing by pressurization is preferred.
Examples of the method for forming the support layer include a method of forming a film by a water-cooled or air-cooled coextrusion inflation method and a coextrusion T-die method. Especially, when the said support layer is a multilayer, since it is excellent in thickness control of each layer, the method of forming into a film by a coextrusion T-die method is preferable.

The release film of the present invention is preferably used in the semiconductor molding process to improve the productivity by coating the inner surface of the mold and prevent the mold from being contaminated by the resin.
However, the use of the release film of the present invention is not limited to the above-mentioned use. For example, a copper-clad laminate or a copper foil is hot-pressed on a substrate via a prepreg or a heat-resistant film, and a printed wiring board, a flexible printed board, or a multilayer is used. When manufacturing a printed wiring board, it may be used to prevent adhesion between the heat-pressed board and the obtained printed wiring board, flexible printed board or multilayer printed wiring board, or via a thermosetting adhesive When a cover lay film is bonded to a substrate on which a copper circuit is formed by hot pressing to manufacture a flexible printed circuit board, the bonding between the hot pressing plate and the cover lay film or the bonding between the cover lay films is prevented. May be used.

ADVANTAGE OF THE INVENTION According to this invention, the mold release film which can be excellent in mold release property, can suppress the outflow of resin also on high temperature molding conditions, and can suppress the defect of a product external appearance can be provided.

Hereinafter, embodiments of the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
A mixed resin of 75 parts by weight of polybutylene terephthalate (PBT) and 25 parts by weight of a PBT elastomer (a copolymer of polybutylene terephthalate and polytetramethylene glycol) was extruded into an extruder (GM Engineering Co., Ltd., GM30-28 (screw diameter 30 mm). L / D28)) and extruded at a T die width of 400 mm to form a support layer.
A thermosetting type fluorine-based release agent was applied to the obtained support layer and thermally cured to form a release layer having a thickness of 0.3 μm.
Furthermore, a release film having a thickness of 50 μm was obtained with a textured finish on both surfaces (surface 10-point average roughness Rz = 12 μm) of the embossed roll.
In addition, the elastic modulus at 170 ° C. was measured using AUTOGRAPH AGS-X (manufactured by Shimadzu Corporation).

( Examples 5-12, Comparative Examples 5-7 )
As shown in Tables 1 and 2, a release film was obtained in the same manner as in Example 1 except that the presence or absence of the satin finish, the Rz value, and the release agent of the release layer were changed.

(Comparative Example 1)
A commercially available fluorine-based release film (tetrafluoroethylene-ethylene copolymer (ETFE), unstretched, “Aflex” manufactured by Asahi Glass Co., Ltd.)) having a concavo-convex process on both sides with a thickness of 50 μm was used as the release film. .

(Comparative Example 2)
A commercially available fluorine-based release film (ETFE, unstretched, “Aflex” manufactured by Asahi Glass Co., Ltd.) with a concavo-convex process on both sides with a thickness of 50 μm is used as a support layer, and the support layer contains (HMDI) and octadecanediol. A release agent made of urethane acrylate was applied and thermally cured to form a release layer having a thickness of 0.3 μm to obtain a release film.

(Comparative Example 3)
Using a commercially available polyethylene terephthalate film (PET, “Lumirror 38F99” manufactured by Toray Industries, Inc.) with a concavo-convex surface on one side having a thickness of 38 μm as a support layer, the support layer is made of urethane acrylate containing (HMDI) and octadecanediol. A release agent having a thickness of 3 μm was formed by applying a release agent and thermosetting to obtain a release film.

(Comparative Example 4)
Polybutylene terephthalate (PBT) was extruded at a T die width of 400 mm using an extruder (GM Engineering Co., Ltd., GM30-28 (screw diameter 30 mm, L / D28)) to obtain a release film having a thickness of 50 μm. .

<Evaluation>
The following evaluation was performed about the release film obtained by the Example and the comparative example. The results are shown in Tables 1 and 2.

(1) Release layer The release layer side of the release film and the epoxy adhesive sheet were stacked and hot-pressed at 170 ° C. and 220 kN for 2 minutes, and then subjected to a 180 ° peel test at a test speed of 500 mm / min. Evaluation was made according to the following criteria.
A: Peeling force is 0 gf / cm (natural peeling)
○: Peeling force exceeds 0 gf / cm but less than 3.0 gf / cm ×: Peeling force is 3.0 gf / cm or more

(2) Follow-up (resin flow)
A coverlay film (having an epoxy adhesive layer) with a hole of φ = 1 mm is placed on a copper-clad laminate (also referred to as CCL), and a release film is further laminated at 170 ° C. and 220 kN for 2 minutes. Hot pressed. At this time, the distance of the epoxy adhesive which flowed into the hole was measured while observing with an optical microscope. Evaluation was made according to the following criteria.
◎: The distance of the flowed epoxy adhesive is less than 60 μm ○: The distance of the flowed epoxy adhesive is 60 μm or more and less than 70 μm ×: The distance of the flowed epoxy adhesive is 70 μm or more

(3) Heat shrinkage rate The release film was heat-treated at 170 ° C. for 30 minutes, and the heat shrinkage rate (MD direction) was calculated by the following formula.
ΔL = [(L1-L0) / L0] × 100
ΔL: thermal shrinkage rate (heating dimensional change rate) (%)
L1: Dimensions after heating (mm)
L0: Dimensions before heating (mm)
Evaluation was made according to the following criteria.
○: −1% ≦ ΔL ≦ 1%
×: Outside the above range

(4) Molded product appearance Using the mold release film, molding was performed by a molding apparatus. The obtained molded product was visually confirmed and evaluated according to the following criteria.
◎: There is no appearance defect and a moderate matting effect is obtained. ○: There is no appearance defect due to flow marks or wrinkles on the surface. △: There is no appearance defect due to wrinkles, but there is a flow mark on the surface. There is a noticeable appearance defect due to

(Example 13)
Polybutylene terephthalate (PBT) was extruded with a T die width of 400 mm using an extruder (GM Engineering Co., Ltd., GM30-28 (screw diameter 30 mm, L / D28)) to form a support layer.
A thermosetting type fluorine-based release agent was applied to the obtained support layer and thermally cured to form a release layer having a thickness of 0.3 μm.
Further, a release film having a thickness of 50 μm was obtained by heating and pressurizing with a roll having an embossed shape so that both surfaces were textured (surface 10-point average roughness Rz = 12 μm of the release layer).
In addition, the elastic modulus at 170 ° C. was measured using AUTOGRAPH AGS-X (manufactured by Shimadzu Corporation).

( Examples 17 to 24, Comparative Examples 8 to 10 )
As shown in Tables 3 and 4, a release film was obtained in the same manner as in Example 1 except that the presence or absence of the satin finish, the Rz value, and the release agent of the release layer were changed.

<Evaluation>
Evaluation similar to the above was performed on the release films obtained in the examples and comparative examples. The results are shown in Tables 3 and 4.

( Comparative Example 11 )
A mixed resin of 75 parts by weight of polybutylene terephthalate (PBT) and 25 parts by weight of a PBT elastomer (a copolymer of polybutylene terephthalate and polytetramethylene glycol) was extruded using an extruder (GM Engineering Co., Ltd., GM30-28 (screw diameter 30 mm, L / D28)) was extruded at a T die width of 400 mm to form a support layer.
A thermosetting type fluorine-based release agent was applied to the obtained support layer and thermally cured to form a release layer having a thickness of 0.3 μm.
Further, a release film having a thickness of 50 μm was obtained by heating and pressurizing with a roll having an embossed shape so that both surfaces were textured (surface 10-point average roughness Rz = 12 μm of the release layer).
In addition, the elastic modulus at 170 ° C. was measured using AUTOGRAPH AGS-X (manufactured by Shimadzu Corporation).

( Examples 28 to 35, Comparative Examples 12 and 13 )
As shown in Table 5, a release film was obtained in the same manner as in Example 1 except that the presence or absence of the satin finish, the Rz value, and the release agent of the release layer were changed.

<Evaluation>
Evaluation similar to the above was performed on the release films obtained in the examples and comparative examples. The results are shown in Table 5.

( Comparative Example 14 )
Polybutylene terephthalate (PBT) was extruded at a T-die width of 400 mm using an extruder (GM Engineering Co., Ltd., GM30-28 (screw diameter 30 mm, L / D28)), and a longitudinal stretching machine and a transverse stretching machine 2 were used. The support layer was formed by stretching three times by axial stretching.
A thermosetting type fluorine-based release agent was applied to the obtained support layer and thermally cured to form a release layer having a thickness of 0.3 μm.
Furthermore, the release film by which it extended 3 times and both surfaces were satin-finished (surface 10 point average roughness Rz = 12 micrometers of a release layer) was obtained by heating and pressurizing with the roll which has an embossed shape.

( Comparative Examples 15-17 )
As shown in Table 6, a release film was obtained in the same manner as in Example 1 except that the presence or absence of the stretching treatment, the presence or absence of the satin finish, the Rz value, and the release agent of the release layer were changed.

<Evaluation>
Evaluation similar to the above was performed on the release films obtained in the examples and comparative examples. The results are shown in Table 6.

ADVANTAGE OF THE INVENTION According to this invention, the mold release film which can be excellent in mold release property, can suppress the outflow of resin also on high temperature molding conditions, and can suppress the defect of a product external appearance can be provided.

Claims (2)

A release film having a support layer having a single layer structure or a multilayer structure having at least one layer containing a polybutylene terephthalate resin, and a release layer,
The support layer is an unstretched resin layer,
A release film characterized in that at least the surface of the release layer side of the release film has been satin-finished, and the ten-point average roughness Rz of the textured surface is 3.0 or more. 2. The release film according to claim 1, wherein the ten-point average roughness Rz of the surface of the release film that has been textured is 15.0 or less.