JP6978994B2 - Transfer film - Google Patents

Description

The present disclosure relates to transfer films .

An electromagnetic wave shielding film is used to protect electronic circuits from electromagnetic waves. The electromagnetic wave shielding film has a conductive adhesive layer and an insulating protective layer. The electromagnetic wave shielding film is generally manufactured by sequentially forming an insulating protective layer and a conductive adhesive layer on the surface of the base film. The substrate film is removed after the electromagnetic wave shielding film is adhered to the printed wiring board and before the reflow step. In this case, the base film functions as a transfer film whose surface state is transferred to the insulating protective layer. It also functions as a protective film that protects the insulating protective layer until the electromagnetic wave shielding film is adhered to the printed wiring board.

In order to make the surface of the insulating protective layer a matte surface, it is common to provide irregularities on the surface of the transfer film. By providing the unevenness, the adhesion between the transfer film and the insulating protective layer is improved, and the force required for peeling the transfer film is increased. Further, when the electromagnetic wave shielding film is adhered to the printed wiring board, it is common to apply a pressure of several MPa at a temperature of about 150 ° C. to 200 ° C. Exposure to such temperatures and pressures makes it even more difficult to peel off the transfer film and may break the transfer film.

In order to prevent breakage during peeling, it has been studied to make the transfer film itself difficult to tear (see, for example, Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 2015-185569 Japanese Unexamined Patent Publication No. 2016-97522

However, even if the transfer film itself is hard to tear, the productivity will decrease if a large force is required for peeling. In addition, the side of the insulating protective layer may be damaged. In order to allow the transfer film to be easily peeled off, it is desired to control the interaction between the transfer film and the insulating protective layer.

An object of the present disclosure is to realize an electromagnetic wave shielding film in which the transfer film can be easily peeled off.

One aspect of the electromagnetic wave shielding film of the present disclosure includes an insulating protective layer, a transfer film provided on the surface of the insulating protective layer, and a conductive adhesive layer provided on the opposite side of the transfer film of the insulating protective layer. The surface of the transfer film on the insulating protective layer side has a maximum valley depth (Sv) of 1 μm or more and 6 μm or less, and a maximum height (Sz) of 2 μm or more and 10 μm or less.

In one aspect of the electromagnetic wave shielding film, the coefficient of variation of the maximum valley depth (Sv) and the coefficient of variation of the maximum height (Sz) on the surface of the transfer film on the insulating protective layer side can be 0.2 or less.

According to the electromagnetic wave shielding film of the present disclosure, the transfer film can be easily peeled off, and the productivity can be improved.

It is sectional drawing which shows the electromagnetic wave shielding film which concerns on one Embodiment. It is sectional drawing which shows the modification of the electromagnetic wave shielding film. It is sectional drawing which shows the shield printed wiring board which used the electromagnetic wave shielding film which concerns on one Embodiment.

As shown in FIG. 1, the electromagnetic wave shielding film of the present embodiment is provided on the opposite side of the insulating protective layer 112, the transfer film 115 provided on the surface of the insulating protective layer 112, and the transfer film 115 of the insulating protective layer 112. It is provided with the obtained conductive adhesive layer 111. As shown in FIG. 2, a shield layer 113 may be provided between the insulating protective layer 112 and the conductive adhesive layer 111.

The inventors of the present application set the maximum valley depth (Sv) on the surface of the transfer film 115 on the side of the insulating protective layer 112 to be 6 μm or less, preferably 5 μm or less, and the maximum height (Sz) to 10 μm or less, preferably 9 μm or less. By doing so, it was found that the transfer film 115 can be easily peeled off.

On the other hand, it was found that there is a film that is difficult to peel off even if the arithmetic mean height (Sa) is small. It is considered that even if the unevenness has the same average value, if there are pinpoint deep valleys or high peaks, the adhesion will be high in that part and peeling will be difficult. Therefore, it is important to control Sv and Sz of the transfer film 115. The Sa, Sv and Sz of the transfer film 115 can be measured by the method described in the examples.

From the viewpoint of facilitating peeling, it is preferable that the maximum valley depth on the surface of the transfer film 115 on the side of the insulating protective layer 112 is small. From the viewpoint of preventing the transfer film 115 from peeling off before fixing, the Sv is 1 μm or more, preferably 2 μm or more, and the Sz is 2 μm or more, preferably 3 μm or more.

The peel strength of the transfer film 115 is preferably 5.0 N / 50 mm or less, more preferably 1.5 N / 50 mm or less from the viewpoint of easy peeling, and from the viewpoint of preventing the transfer film 115 from peeling before use. It is preferably 0.2 N / 50 mm or more, more preferably 0.5 N / 50 mm or more. The peel strength of the transfer film 115 can be measured by the method shown in Examples.

From the viewpoint of facilitating peeling, the coefficient of variation of Sv and the coefficient of variation (CV) of Sz on the surface of the transfer film 115 on the side of the insulating protective layer 112 are preferably 0.2 or less, more preferably 0.15 or less. do. The coefficient of variation referred to here is a value obtained from an arithmetic mean and standard deviation of 10 points as shown in Examples.

Further, from the viewpoint of further facilitating peeling, it is preferable to control parameters representing surface texture other than Sv and Sz. For example, the sharpness (Sku) is preferably 2.0 or more, more preferably 3.0 or more, preferably 8.5 or less, and more preferably 7.5 or less. The minimum autocorrelation length (Sal) is preferably 7.5 μm or more, more preferably 8.5 μm or more, preferably 20.0 μm or less, and more preferably 15.0 or less. The aspect ratio (Str) of the surface texture is preferably 0.55 or more, more preferably 0.60 or more, and preferably 0.75 or less. The protruding valley height (Svk) is preferably 0.20 or more, more preferably 0.25 or more, preferably 0.75 or less, and more preferably 0.70 or less. The load area ratio (Smr2) for separating the protruding valley portion and the core portion is preferably 90.0% or more, more preferably 94.0% or more. The parameters representing these surface textures can also be measured by the method shown in the examples.

The material of the transfer film 115 is not particularly limited, and polyester, polyolefin, polyimide, polyethylene naphthalate, pofiphenylene sulfide and the like can be used. The thickness of the transfer film 115 is not particularly limited, but is preferably 25 μm or more, preferably 100 μm or less, from the viewpoint of facilitating peeling.

At least one surface of the transfer film 115 may be sandblasted or the like in order to set Sv and Sz to predetermined values. Further, by containing fine particles, Sv and Sz can be set to predetermined values. The fine particles added to the transfer film 115 are not particularly limited, and are, for example, amorphous silica (colloidal silica), silica, talc, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, and phosphoric acid. Inorganic particles such as magnesium, alumina, carbon black, titanium dioxide, kaolin, and synthetic zeolite, and organic particles such as crosslinked polystyrene particles and crosslinked acrylic particles can be used.

A mold release agent layer (not shown) can be provided between the transfer film 115 and the insulating protective layer 112. The release agent layer can be formed by applying a silicon-based or non-silicon-based release agent to the surface of the transfer film 115 on the insulating protective layer 112 side. When forming the release agent layer, the thickness thereof can be about several μm to several several μm.

In the present embodiment, the insulating protective layer 112 has sufficient insulating properties and is not particularly limited as long as it can protect the conductive adhesive layer 111 and the shield layer 113 if necessary, but for example, a thermoplastic resin and thermosetting. It can be formed by using a sex resin, an active energy ray curable resin, or the like.

The thermoplastic resin is not particularly limited, but a styrene resin, a vinyl acetate resin, a polyester resin, a polyethylene resin, a polypropylene resin, an imide resin, an acrylic resin and the like can be used. The thermosetting resin is not particularly limited, but a phenol-based resin, an epoxy-based resin, a urethane-based resin, a melamine-based resin, a polyamide-based resin, an alkyd-based resin, or the like can be used. The active energy ray-curable resin is not particularly limited, and for example, a polymerizable compound having at least two (meth) acryloyloxy groups in the molecule can be used. The protective layer may be formed of a single material or may be formed of two or more kinds of materials.

The insulating protective layer 112 is not limited to a colorant, but is not limited to a colorant, but is a curing accelerator, a tackifier, an antioxidant, a plasticizer, an ultraviolet absorber, an antifoaming agent, a leveling agent, a filler, a flame retardant, and a viscosity. It may contain one or more modifiers, anti-blocking agents and the like.

The insulating protective layer 112 may be a laminated body having two or more layers having different physical properties such as material, hardness, and elastic modulus. For example, in the case of a laminate of an outer layer having a low hardness and an inner layer having a high hardness, the outer layer has a cushioning effect, so that the pressure applied to the shield layer 113 in the step of heating and pressurizing the electromagnetic wave shield film 101 to the printed wiring substrate 102 is applied. Can be relaxed. Therefore, it is possible to prevent the shield layer 113 from being destroyed by the step provided on the printed wiring board 102.

The insulating protective layer 112 can be formed by applying the insulating protective layer composition to the surface of the transfer film 115. The composition for the insulating protective layer may be prepared, for example, by adding an appropriate amount of solvent to the resin for the insulating protective layer.

The thickness of the insulating protective layer 112 is not particularly limited and can be appropriately set as needed, but is preferably 1 μm or more, more preferably 4 μm or more, and preferably 20 μm or less, more preferably 10 μm or less, and further. It can be preferably 5 μm or less. By setting the thickness of the insulating protective layer 112 to 1 μm or more, the conductive adhesive layer 111 and the shield layer 113 can be sufficiently protected. By setting the thickness of the insulating protective layer 112 to 20 μm or less, it becomes easy to set the elastic modulus and the elongation at break of the electromagnetic wave shielding film 101 to predetermined values.

When the shield layer 113 is provided, the shield layer 113 can be formed of a metal foil, a vapor-deposited film, a conductive filler, or the like.

The metal foil is not particularly limited, but may be a foil made of any one of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc and the like, or an alloy containing two or more of them.

The thickness of the metal foil is not particularly limited, but is preferably 0.5 μm or more, and more preferably 1.0 μm or more. When the thickness of the metal foil is 0.5 μm or more, it is possible to suppress the attenuation of the high frequency signal when the high frequency signal of 10 MHz to 100 GHz is transmitted to the shield printed wiring board. The thickness of the metal foil is preferably 12 μm or less, more preferably 10 μm or less, and even more preferably 7 μm or less. When the thickness of the metal layer is 12 μm or less, the raw material cost can be suppressed and the judgment elongation of the shield film becomes good.

The vapor deposition film is not particularly limited, but can be formed by vapor deposition of nickel, copper, silver, tin, gold, palladium, aluminum, chromium, titanium, zinc and the like. For the vapor deposition, an electrolytic plating method, a non-electroplating plating method, a sputtering method, an electron beam vapor deposition method, a vacuum vapor deposition method, a chemical vapor deposition (CVD) method, a metal organic deposition (MOCVD) method, or the like can be used.

The thickness of the thin-film film is not particularly limited, but is preferably 0.05 μm or more, and more preferably 0.1 μm or more. When the thickness of the metal vapor-deposited film is 0.05 μm or more, the electromagnetic wave shielding film has excellent characteristics of shielding electromagnetic waves in the shield-printed wiring substrate. The thickness of the metal vapor deposition film is preferably less than 0.5 μm, more preferably less than 0.3 μm. When the thickness of the metal vapor-deposited film is less than 0.5 μm, the bending resistance of the electromagnetic wave shielding film is excellent, and it is possible to prevent the shield layer from being destroyed by the step provided on the printed wiring board.

In the case of the conductive filler, the shield layer 113 can be formed by applying a solvent containing the conductive filler to the surface of the insulating protective layer 112 and drying it. As the conductive filler, a metal filler, a metal-coated resin filler, a carbon filler, or a mixture thereof can be used. As the metal filler, copper powder, silver powder, nickel powder, silver coat copper powder, gold-coated copper powder, silver-coated nickel powder, gold-coated nickel powder and the like can be used. These metal powders can be produced by an electrolytic method, an atomizing method, or a reducing method. Examples of the shape of the metal powder include a spherical shape, a flake shape, a fibrous shape, and a dendritic shape.

In the present embodiment, the thickness of the shield layer 113 may be appropriately selected according to the required electromagnetic shielding effect and repeated bending / sliding resistance, but in the case of a metal foil, it is 12 μm from the viewpoint of ensuring breaking elongation. The following is preferable.

In the present embodiment, the conductive adhesive layer 111 contains a resin component such as a thermoplastic resin and a thermosetting resin, and a conductive filler.

When the conductive adhesive layer 111 contains a thermoplastic resin, the thermoplastic resin may be, for example, a styrene resin, a vinyl acetate resin, a polyester resin, a polyethylene resin, a polypropylene resin, an imide resin, an acrylic resin or the like. Can be used. These resins may be used alone or in combination of two or more.

When the conductive adhesive layer 111 contains a thermosetting resin, for example, a phenol-based resin, an epoxy-based resin, a urethane-based resin, a melamine-based resin, a polyamide-based resin, an alkyd-based resin, or the like can be used as the thermosetting resin. .. The active energy ray-curable composition is not particularly limited, and for example, a polymerizable compound having at least two (meth) acryloyloxy groups in the molecule can be used. These compositions may be used alone or in combination of two or more.

The thermosetting resin contains, for example, a first resin component having a reactive first functional group and a second resin component that reacts with the first functional group. The first functional group can be, for example, an epoxy group, an amide group, a hydroxyl group, or the like. The second functional group may be selected according to the first functional group. For example, when the first functional group is an epoxy group, it may be a hydroxyl group, a carboxyl group, an epoxy group, an amino group or the like. Specifically, for example, when the first resin component is an epoxy resin, the second resin component is an epoxy group-modified polyester resin, an epoxy group-modified polyamide resin, an epoxy group-modified acrylic resin, an epoxy group-modified polyurethane polyurea resin, or a carboxyl. Basically modified polyester resin, carboxyl group modified polyamide resin, carboxyl group modified acrylic resin, carboxyl group modified polyurethane polyurea resin, urethane modified polyester resin and the like can be used. Among these, a carboxyl group-modified polyester resin, a carboxyl group-modified polyamide resin, a carboxyl group-modified polyurethane polyurea resin, and a urethane-modified polyester resin are preferable. When the first resin component is a hydroxyl group, the second resin component includes an epoxy group-modified polyester resin, an epoxy group-modified polyamide resin, an epoxy group-modified acrylic resin, an epoxy group-modified polyurethane polyurea resin, and a carboxyl group-modified polyester resin. A carboxyl group-modified polyamide resin, a carboxyl group-modified acrylic resin, a carboxyl group-modified polyurethane polyurea resin, a urethane-modified polyester resin, and the like can be used. Among these, a carboxyl group-modified polyester resin, a carboxyl group-modified polyamide resin, a carboxyl group-modified polyurethane polyurea resin, and a urethane-modified polyester resin are preferable.

The thermosetting resin may contain a curing agent that promotes a thermosetting reaction. When the thermosetting resin has a first functional group and a second functional group, the curing agent can be appropriately selected depending on the type of the first functional group and the second functional group. When the first functional group is an epoxy group and the second functional group is a hydroxyl group, an imidazole-based curing agent, a phenol-based curing agent, a cationic-based curing agent, or the like can be used. These can be used alone or in combination of two or more. In addition, an antifoaming agent, an antioxidant, a viscosity modifier, a diluent, an antioxidant, a leveling agent, a coupling agent, a coloring agent, a flame retardant and the like may be contained as optional components.

The conductive filler is not particularly limited, and for example, a metal filler, a metal-coated resin filler, a carbon filler, and a mixture thereof can be used. Examples of the metal filler include copper powder, silver powder, nickel powder, silver coat copper powder, gold-coated copper powder, silver-coated nickel powder, and gold-coated nickel powder. These metal powders can be produced by an electrolytic method, an atomizing method, a reducing method, or the like. Of these, any of silver powder, silver-coated copper powder and copper powder is preferable.

From the viewpoint of contact between the fillers, the conductive filler has an average particle size of preferably 1 μm or more, more preferably 3 μm or more, preferably 50 μm or less, and more preferably 40 μm or less. The shape of the conductive filler is not particularly limited, and may be spherical, flake-shaped, dendritic, fibrous, or the like.

The content of the conductive filler can be appropriately selected depending on the intended use, but is preferably 5% by mass or more, more preferably 10% by mass or more, preferably 95% by mass or less, more preferably 95% by mass or less in the total solid content. It is 90% by mass or less. From the viewpoint of embedding property, it is preferably 70% by mass or less, more preferably 60% by mass or less. Further, in the case of realizing anisotropic conductivity, it is preferably 40% by mass or less, more preferably 35% by mass or less.

The conductive adhesive layer 111 can be formed, for example, by applying the composition for a conductive adhesive layer on the insulating protective layer 112 or the shield layer 113 formed on the insulating protective layer 112. The composition for the conductive adhesive layer may be prepared by adding an appropriate amount of solvent to the resin and filler for the conductive adhesive layer.

The thickness of the conductive adhesive layer 111 is preferably 1 μm to 50 μm from the viewpoint of controlling the embedding property.

If necessary, a peelable protective film may be attached to the surface of the conductive adhesive layer 111.

As shown in FIG. 3, the electromagnetic wave shielding film 101 of the present embodiment can be combined with the printed wiring board 102 to form a shielded wiring board 103. The electromagnetic wave shielding film 101 may have a shielding layer 113.

The printed wiring board 102 has, for example, a printed circuit including a base member 122 and a ground circuit 125 provided on the base member 122. The insulating film 121 is adhered on the base member 122 by the adhesive layer 123. The insulating film 121 is provided with an opening that exposes the ground circuit 125. A surface layer such as a gold plating layer may be provided on the exposed portion of the ground circuit 125. The printed wiring board 102 may be a flexible board or a rigid board.

When the electromagnetic wave shielding film 101 is adhered to the printed wiring board 102, the electromagnetic wave shielding film 101 is arranged on the printed wiring board 102 so that the conductive adhesive layer 111 is located above the opening. Then, the electromagnetic wave shield film 101 and the printed wiring board 102 are sandwiched from above and below by two heating plates (not shown) heated to a predetermined temperature (for example, 120 ° C.), and a predetermined pressure (for example, 0.5 MPa) is sandwiched between them. ) For a short time (for example, 5 seconds). As a result, the electromagnetic wave shielding film 101 is temporarily fixed to the printed wiring board 102.

Subsequently, the temperature of the two heating plates is set to a predetermined temperature (for example, 170 ° C.) higher than that at the time of the temporary fixing, and the pressure is applied at a predetermined pressure (for example, 3 MPa) for a predetermined time (for example, 30 minutes). As a result, the electromagnetic wave shielding film 101 can be fixed to the printed wiring board 102. When the pressure is applied, the conductive adhesive layer 111 is sufficiently embedded in the opening, so that the strength and conductivity required by the electromagnetic wave shielding film 101 can be realized.

After fixing the electromagnetic wave shielding film 101 to the printed wiring board 102, the transfer film 115 is peeled off. After that, solder reflow for component mounting is performed. In the electromagnetic wave shielding film 101 of the present embodiment, the transfer film 115 can be easily peeled off after the electromagnetic wave shielding film 101 is fixed to the printed wiring substrate 102, so that the production efficiency can be improved and the competition can be made.

Hereinafter, the electromagnetic wave shielding film of the present disclosure will be described in more detail using examples. The following examples are exemplary and are not intended to limit the invention.

<Making an electromagnetic wave shield film>
A mold release agent was applied to the surface of a predetermined transfer film. The composition for the insulating protective layer was applied to the surface of the transfer film coated with the release agent using a wire bar, and heated and dried to form the insulating protective layer. Next, the composition for the conductive adhesive layer was applied onto the insulating protective layer with a wire bar, and then dried at 100 ° C. for 3 minutes to prepare an electromagnetic wave shielding film.

The composition for the insulating protective layer has a two-layer structure consisting of a hard coat layer of a polyester-based transparent resin having a thickness of 2 μm and a soft coat layer of a carbon black-containing epoxy-based black resin having a thickness of 3 μm. The composition for the conductive adhesive layer was prepared by adding a dendritic silver-coated copper powder having an average particle diameter of 5 μm as conductive fine particles to a phosphorus-based flame retardant-containing epoxy resin. The thickness of the conductive adhesive layer was 15 μm.

<Measurement of surface texture>
The parameters related to the surface texture were measured according to ISO25178 using a laser microscope (VK-X210, manufactured by KEYENCE CORPORATION, lens magnification 50 times). The measurement was performed on the surface of the unused transfer film cut out to 5.0 cm × 5.0 cm to form the insulating protective layer. Measurements were made at any 10 points in the plane, and the arithmetic mean value was adopted as the measured value. In addition, the standard deviation (SD) and the coefficient of variation (CV) were calculated.

<Measurement of peel strength>
The electromagnetic wave shield film was pressed using a press machine under the conditions of temperature: 170 ° C., time: 30 minutes, and pressure: 2 to 3 MPa. After the electromagnetic wave shielding film returned to room temperature, the peeling strength of the transfer film was measured using a peeling strength tester (PFT50S, manufactured by Palmec Co., Ltd.) for the peeling film on the surface. The measurement was performed at room temperature under the conditions of a tensile speed of 1000 mm / min and a peeling angle of 170 °. The measurement was performed 10 times, and the minimum value, the maximum value and the average value were obtained.

(Example 1)
A PET film having a thickness of 50 μm was used as the transfer film. The surface of the insulating protective layer after the transfer film was peeled off was a matte surface. The Sv on the insulating protective layer forming surface of the transfer film was 3.1 μm, the Sz was 8.0 μm, and the Sa was 0.69 μm. The coefficient of variation of Sv was 0.15, and the coefficient of variation of Sz was 0.02. The minimum value of the peel strength was 0.51 N / 50 mm, the maximum value was 0.75 N / 50 mm, and the average value was 0.63 N / 50 mm.

(Example 2)
A PET film having a thickness of 50 μm was used as the transfer film. The surface of the insulating protective layer after the transfer film was peeled off was a matte surface. The Sv on the insulating protective layer forming surface of the transfer film was 2.5 μm, the Sz was 6.6 μm, and the Sa was 0.41 μm. The coefficient of variation of Sv was 0.12, and the coefficient of variation of Sz was 0.08. The minimum value of the peel strength was 0.60 N / 50 mm, the maximum value was 0.76 N / 50 mm, and the average value was 0.68 N / 50 mm.

(Example 3)
A PET film having a thickness of 50 μm was used as the transfer film. The surface of the insulating protective layer after the transfer film was peeled off was a matte surface. The Sv on the insulating protective layer forming surface of the transfer film was 5.9 μm, the Sz was 9.6 μm, and the Sa was 0.69 μm. The coefficient of variation of Sv was 0.07, and the coefficient of variation of Sz was 0.09. The minimum value of the peel strength was 0.98 N / 50 mm, the maximum value was 1.50 N / 50 mm, and the average value was 1.25 N / 50 mm.

(Comparative Example 1)
A PET film having a thickness of 50 μm was used as the transfer film. The surface of the insulating protective layer after the transfer film was peeled off was a matte surface. The Sv on the insulating protective layer forming surface of the transfer film was 6.8 μm, the Sz was 11.4 μm, and the Sa was 0.48 μm. The coefficient of variation of Sv was 0.43, and the coefficient of variation of Sz was 0.40. The minimum value of the peel strength was 7.0 N / 50 mm, and the maximum value exceeded 10 N / 50 mm, so that it could not be measured.

(Comparative Example 2)
A PET film having a thickness of 50 μm was used as the transfer film. The surface of the insulating protective layer after the transfer film was peeled off was a glossy surface. Sv on the insulating protective layer forming surface of the transfer film was 0.8 μm, Sz was 1.3 μm, and Sa was 0.06 μm. The coefficient of variation of Sv was 0.23, and the coefficient of variation of Sz was 0.13. The minimum value of the peel strength was 0.08 N / 50 mm, the maximum value was 0.15 N / 50 mm, and the average value was 0.10 N / 50 mm.

Table 1 summarizes the results of each example and comparative example. In addition to Sv and Sz, sharpness (Sku), minimum autocorrelation length (Sal), surface aspect ratio (Str), protruding valley height (Svk), and load separating the protruding valley and core. Data is also described for the area ratio (Smr2).

The electromagnetic wave shielding film of the present disclosure can easily peel off the transfer film and improve productivity.

101 Electromagnetic wave shield film 102 Printed wiring board 103 Shield wiring board 111 Conductive adhesive layer 112 Insulation protection layer 113 Shield layer 115 Transfer film 121 Insulation film 122 Base member 123 Adhesive layer 125 Ground circuit

Claims (4)

A transfer film in which a resin layer is formed on a resin layer forming surface coated with a mold release agent, and the surface of the resin layer is used as a matte surface due to the unevenness of the resin layer forming surface.
The resin layer forming surface of the transfer film has a maximum valley depth (Sv) of 1 μm or more and 5 μm or less, a maximum height (Sz) of 2 μm or more and 9 m or less, and a minimum autocorrelation length (Sal) of 8. A transfer film having a thickness of .5 μm or more and 20 μm or less. The transfer film according to claim 1, wherein the coefficient of variation of the maximum valley depth (Sv) and the coefficient of variation of the maximum height (Sz) on the resin layer forming surface of the transfer film are 0.2 or less. The transfer film according to claim 1 or 2, wherein the load area ratio (Smr2) for separating the protruding valley portion and the core portion on the resin layer forming surface of the transfer film is 90% or more. The transfer film according to any one of claims 1 to 3, which contains fine particles.

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