JP2022052887A - Release film and functional film - Google Patents

Abstract

To provide a release film that allows a functional layer to be applied onto a rugged adherend such as an electronic component-mounted substrate with high accuracy of coating, and provide a functional film having the release film and the functional layer.SOLUTION: A release film has a cushion layer, and a release layer laminated on one side of the cushion layer. When the release film is subjected to viscoelasticity measurement at a temperature of 120°C, a frequency of 1 Hz, and in a torsional mode, the value of I, defined by the formula I=(G'/100000)/tanδ, is 3.5 or more, where G'[Pa] is a storage elastic modulus measured 300 seconds after the start of measurement and tanδ is a loss tangent.SELECTED DRAWING: Figure 1

Description

The present invention relates to a release film and a functional film.

In electronic devices such as mobile phones, smartphones, calculators, electronic newspapers, tablet terminals, videophones, and personal computers, for example, electronic component mounting substrates such as semiconductor elements, capacitors, and coils are mounted on the substrate. Is implemented. Such an electronic component mounting substrate may be sealed with a functional resin layer in order to prevent contact with external factors such as moisture and dust.

For sealing with such a resin, for example, in addition to a potting method in which a substrate on which an electronic component is mounted is placed in a metal cavity and then a thermosetting resin such as a highly fluid urethane resin is injected and sealed, heat is used. A coating method is known in which a plastic resin is applied to an electronic component mounting substrate in a molten state and then solidified to coat (seal) the applied area.

However, in the potting method, it takes time to cure the thermosetting resin, and further, since a metal cavity is usually required for sealing, there is a problem that the weight of the obtained electronic device is increased. Further, in the coating method, there is a problem that it takes time and effort to control the viscosity of the thermoplastic resin to be in a molten state and to separately coat the coated area of the thermoplastic resin.

For the purpose of solving the above-mentioned problems, it has been proposed to attach a barrier film having a hot melt property to an electronic component mounting substrate as a protective layer (functional layer) (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2009-9417

In the encapsulation of an electronic component mounting substrate by attaching a film as in Patent Document 1, the protective layer does not sufficiently follow the unevenness caused by the electronic component mounting substrate provided with the electronic component, and the protective layer does not sufficiently follow the unevenness. As a result, it may not be possible to sufficiently obtain a barrier effect against external factors such as moisture and dust.

In particular, in the region of the electronic component mounting board in which a plurality of electronic components are arranged in a grid pattern, the side surface of the electronic component forming the convex portion of the unevenness when the electronic component mounting board is coated with the protective layer. , And the protective layer may not sufficiently follow the upper surface of the substrate constituting the recess.

The present invention has been made in view of such circumstances. An object of the present invention is to provide a release film used for coating a functional layer on an adherend having irregularities such as an electronic component mounting substrate with excellent coating accuracy, and to provide a release film. It is to provide a functional film which has a mold film and a functional layer.

The present inventors have completed the inventions provided below and solved the above problems.

According to the present invention, the following release films are provided.
A release film comprising a cushion layer and a release layer laminated on one surface of the cushion layer.
When the viscoelasticity of the release film was measured under the conditions of a temperature of 120 ° C., a frequency of 1 Hz, and a twist mode, the storage elastic modulus measured 300 seconds after the start of measurement was G'[Pa], and the loss positive contact was tanδ. When the value of I defined in the following formula is 3.5 or more, the release film.
I = (G'/ 1000000) / tanδ

Further, according to the present invention,
With the above release film,
Provided is a functional film comprising a functional layer laminated on the release layer of the release film.

According to the present invention, there is provided a release film capable of coating a functional layer on a substrate on which an electronic component has irregularities with excellent coating accuracy. Further, according to the present invention, a functional film having the release film and the functional layer is provided.

It is a vertical sectional view which shows a part of embodiment of the functional layer-covered electronic component mounting substrate manufactured by using the functional film of this embodiment. It is a top view which shows the electronic component mounting substrate included in the functional layer covering electronic component mounting substrate shown in FIG. 1. It is a vertical sectional view for demonstrating the manufacturing method which manufactures the functional layer-covered electronic component mounting substrate shown in FIG. 1 using the functional film of this embodiment. FIG. 3B is a plan view showing a state in which the functional film of the present invention is arranged on an electronic component mounting substrate. It is sectional drawing of the functional film of this embodiment. It is sectional drawing of the release film of this embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In all drawings, similar components are designated by the same reference numerals, and description thereof will be omitted as appropriate.
In order to avoid complication, (i) when there are a plurality of the same components in the same drawing, only one of them is coded and all of them are not coded, or (ii) especially the figure. In the second and subsequent stages, the same components as in FIG. 1 may not be designated again.
All drawings are for illustration purposes only. The shape and dimensional ratio of each member in the drawing do not necessarily correspond to the actual article.

In the present specification, the notation "XY" in the description of the numerical range indicates X or more and Y or less unless otherwise specified. For example, "1 to 5% by mass" means "1% by mass or more and 5% by mass or less".

In the notation of a group (atomic group) in the present specification, the notation that does not indicate whether it is substituted or unsubstituted includes both those having no substituent and those having a substituent. For example, the "alkyl group" includes not only an alkyl group having no substituent (unsubstituted alkyl group) but also an alkyl group having a substituent (substituted alkyl group).

The notation "(meth) acrylic" herein represents a concept that includes both acrylic and methacrylic. The same applies to similar notations such as "(meth) acrylate".

As shown in FIG. 6, the release film (release film 1) of the present embodiment includes a cushion layer 13 and a release layer 11 provided on one surface of the cushion layer 13. The release film 1 may have the secondary release layer 12 on the surface of the cushion layer 13 opposite to the side on which the release layer 11 is provided. When the release film 1 is used as the release film of the functional film, as shown in FIG. 5, in the functional film 100, the functional layer 3 is laminated on the surface of the release layer 11 of the release film 1. The structure, in other words, the functional layer 3 / the release layer 11 / the cushion layer 13 / the sub-release layer 12 can have a structure in which they are laminated in this order.

A method of using the functional film 100 including the release film 1 will be described with reference to FIGS. 2 to 4.

[Board for mounting electronic components coated with functional layer]
The functional film of the present embodiment is used for manufacturing an electronic component mounting substrate coated with a functional layer (sometimes referred to as a "functional layer covering component mounting substrate" in the present specification). FIG. 1 is a vertical sectional view of a functional layer-coated electronic component mounting substrate 50 manufactured by using the functional film of the present embodiment, and FIG. 2 is an electron included in the functional layer-coated electronic component mounting substrate 50 shown in FIG. It is a top view which shows the component mounting board 45.
In the following description, the upper side in FIG. 1, the front side of the paper surface in FIG. 2, the lower side in FIG. 1, and the back side of the paper surface in FIG. 2 are referred to as “lower”.

The functional layer-coated electronic component mounting substrate 50 (electronic device) of FIG. 1 is composed of a substrate 5, an electronic component 4 mounted (mounted) on the substrate 5, and an electron composed of the substrate 5 and the electronic component 4. It has a component mounting board 45 and a functional layer 3 that covers the electronic component mounting board 45 on the upper surface side of the board 5.

The substrate 5 is a flat plate for supporting the electronic component 4, and its plan view shape is usually a quadrangle such as a square or a rectangle. The substrate 5 includes, for example, a sheet-shaped wiring (wiring plate) and a resin layer that covers the wiring above and below the sheet, and the wiring is exposed at a position corresponding to a terminal of the electronic component 4. It is composed of a printed wiring board having a part.

Examples of the electronic component 4 include semiconductor elements, capacitors, coils, connectors, resistors and the like.
The electronic component 4 is mounted on the substrate 5 in a state where the terminals of the electronic component 4 are electrically connected to the wiring in the above-mentioned exposed portion.
In the present embodiment, a plurality of electronic components 4 having the same shape are arranged in a grid pattern (matrix shape) on the substrate 5 in the regions shown in FIGS. 1 and 2.

The substrate 5 and the electronic component 4 constitute an electronic component mounting substrate 45 (sticking substrate). In the electronic component mounting substrate 45, by mounting the electronic component 4 on the substrate 5, an unevenness 6 composed of a convex portion 61 and a concave portion 62 is formed on the substrate 5 (FIGS. 1, FIG. 2, FIG. 3 (a). )reference). In particular, in the regions shown in FIGS. 1 and 2, a plurality of electronic components 4 having the same shape are arranged in a grid pattern on the substrate 5, so that a plurality of recesses 62 formed along the X direction and Y A plurality of recesses 62 formed along the direction are formed side by side in a state of being orthogonal to each other (crossing at 90 °) at the cross portion 63 where these are overlapped with each other.

The functional layer 3 is provided so as to cover the upper surface of the electronic component 4, the side surface of the electronic component 4, and the upper surface of the substrate 5 exposed from the electronic component 4. As a result, the unevenness 6 formed by mounting the electronic component 4 on the substrate 5 is covered.
The functional layer 3 functions as a protective layer having, for example, waterproof, dustproof, antifouling, and the like. The functional layer 3 functions to suppress or prevent contact of the electronic component mounting substrate 45, particularly the electronic component 4, with external factors such as moisture and dust.

The electronic components 4 mounted on the substrate 5 have the same shape in the regions shown in FIGS. 1 and 2, and are arranged in a grid pattern. However, the arrangement is not limited to such a configuration, and the electronic components 4 may be randomly arranged, for example, in the regions shown in FIGS. 1 and 2, having different shapes. Further, other than the regions shown in FIGS. 1 and 2, those having the same shape may be arranged in a grid pattern, or those having different shapes may be randomly arranged.

[Manufacturing method of board for mounting electronic components coated with functional layer]
The functional layer-coated electronic component mounting substrate 50 can be manufactured by using the functional film of the present embodiment.

The functional layer-coated electronic component mounting substrate 50 is manufactured by coating the unevenness 6 included in the electronic component mounting substrate 45 with the functional film of the present embodiment. Specifically, the functional layer-coated electronic component mounting substrate 50 can be obtained as follows.
First, the functional film 100 composed of the release film 1 and the functional layer 3 is arranged on the electronic component mounting substrate 45 so that the functional layer 3 is on the electronic component mounting substrate 45 side.
After that, the cushion layer 13 or, if present, the sub-release layer 12 is hot-pressed to push the functional layer 3 corresponding to the shape of the unevenness 6, and the unevenness 6 is covered with the functional layer 3.
The details of the manufacturing method of the functional layer-coated electronic component mounting substrate 50 are described below.

FIG. 3 is a vertical sectional view showing a method of manufacturing the functional layer-coated electronic component mounting substrate 50 shown in FIG. 1 using the functional film 100 of the present embodiment. FIG. 4 is a plan view showing a state in which the functional film 100 of the present embodiment is arranged with respect to the electronic component mounting substrate 45 in FIG. 3 (b). FIG. 5 is a vertical sectional view of the functional film 100 of the present embodiment.
In the following description, the upper side in FIG. 3 and the front side of the paper surface in FIG. 4 are referred to as “upper”, and the lower side in FIG. 3 and the back side of the paper surface in FIG. 4 are referred to as “lower”.

[1] First, as a substrate for attachment, an electronic component mounting substrate 45 on which the electronic component 4 is mounted is prepared on the substrate 5 (preparation step). The electronic component mounting board 45 mounts the electronic component 4 on the substrate 5 so that the terminal of the electronic component 4 is electrically connected to the wiring in the exposed portion where the wiring of the substrate 5 is exposed from the resin layer. Can be obtained by
In the substrate 5, the exposed portions where the wiring is exposed from the resin layer are usually formed in the same number as the number of terminals included in the electronic component 4 corresponding to the position where the electronic component 4 should be mounted. The electronic component 4 is mounted on the substrate 5 by electrical connection with the terminal of the electronic component 4 corresponding to the exposed portion.

When the electronic component 4 is mounted on the substrate 5, the electronic component 4 is arranged on the substrate 5 in a grid pattern (matrix shape) in the regions shown in FIGS. 1 and 2. Due to such an arrangement of the electronic components 4, the side surfaces of the electronic components 4 are exposed between the adjacent electronic components 4 along two directions orthogonal to each other in the X direction (short direction) and the Y direction (longitudinal direction). The recesses 62 are arranged side by side. That is, the plurality of recesses 62 formed along the X direction and the plurality of recesses 62 formed along the Y direction are formed in a state of being orthogonal to each other (crossing at 90 °) at the cross portion 63 where they overlap each other. Will be done.

[2] Next, the functional film 100 of the present embodiment is used to form a functional layer 3 that covers the upper surface and side surfaces of the electronic component 4 and the upper surface of the substrate 5 exposed from the electronic component 4 (functional layer formation). Process).

In the present embodiment, the functional film 100 is a laminate in which the functional layer 3 and the release film 1 are laminated, and the release film 1 is the release layer 11, the cushion layer 13, and the secondary release layer 12. Explains the case where the functional film 100 is a laminated body in which the functional layer 3, the release layer 11, the cushion layer 13, and the sub-release layer 12 are laminated in this order. do.

[2-1] First, the release film 1 which is a laminated body in which the release layer 11, the cushion layer 13, and the secondary release layer 12 are laminated in this order, and the release layer 11 of the release film 1 are laminated. A functional film 100 having the functional layer 3 is prepared (see FIG. 3A), and the electronic component mounting substrate 45 is on the surface side (upper surface side) on which the electronic component 4 is mounted on the substrate 5. The functional film 100 is laminated (pasted) on the electronic component 4 with the functional layer 3 on the electronic component 4 side (see FIG. 3 (c); pasting step).

The method of attaching the functional film 100 to the electronic component 4 is not particularly limited, and examples thereof include a vacuum compressed air molding method and a press molding method.

The vacuum pressure pneumatic forming method is a method of covering the upper surface and the side surface of the electronic component 4 and the upper surface of the substrate 5 exposed from the electronic component 4 with the functional film 100 by using, for example, a vacuum pressure type laminator. In the vacuum pressure pneumatic molding method, first, as shown in FIG. 3B, in a closed space that can be under a vacuum atmosphere, the surface of the electronic component 4 opposite to the substrate 5 and the functional layer 3 side of the functional film 100 The electronic component mounting substrate 45 and the functional film 00 are set in a state of being overlapped with each other so as to face each other. Then, under heating, the closed space is placed in a vacuum atmosphere so that the functional film 100 and the electronic component 4 included in the electronic component mounting substrate 45 are uniformly close to each other from the functional film 100 side, and then added. It is carried out by pressing.

As described above, by uniformly pressurizing from the functional film 100 side and creating a vacuum atmosphere in the closed space, the release film 1 pushes the functional layer 3 corresponding to the shape of the recess 62, and in addition to this pushing. The functional layer 3 located on the electronic component 4 side of the release film 1 is deformed to follow the shape of the recess 62. As a result, as shown in FIG. 3C, the upper surface and the side surface of the electronic component 4 and the upper surface of the substrate 5 exposed from the electronic component 4 in a state where the functional layer 3 is pushed in following the shape of the recess 62. Is covered with the functional layer 3.

On the other hand, in the press molding method, for example, the functional film 100 is placed on the electronic component 4 mounted on the substrate 5, and then the cushion material is placed on the functional film 100. It is a method carried out by holding two flat plates from the upper surface side and the lower surface side thereof, and then bringing the two flat plates close to each other and pressurizing them.

In the press molding method, first, the release film 1 corresponds to the shape of the recess 62 by bringing the functional film 100 and the electronic component 4 close to each other with the cushion material placed on the functional film 100. The functional layer 3 is pushed in, and by this pushing, the functional layer 3 located on the electronic component 4 side of the release film 1 is deformed so as to follow the shape of the recess 62. As a result, as shown in FIG. 3C, the upper surface and side surfaces of the electronic component 4 and the substrate 5 exposed from the electronic component 4 in a state where the functional layer 3 is pushed in following the shape of the recess 62. The upper surface is covered with the functional layer 3.

In the pasting step [2-1] using the vacuum compressed air molding method or the press molding method, the sticking temperature is set to a relatively low temperature region when the functional film 100 having the above-mentioned structure is used. Is preferable. Specifically, the temperature is preferably 90 ° C. or higher and 140 ° C. or lower, more preferably 100 ° C. or higher and 130 ° C. or lower, and further preferably 110 ° C. or higher and 120 ° C. or lower. By appropriately setting the heating temperature of the functional film 100 when the vacuum compressed air forming method or the press forming method is used, the functional layer 3 has excellent coating accuracy on the side surface of the electronic component 4 and the upper surface of the substrate 5. Can be covered with.
The pressure to be applied is not particularly limited, but is preferably 0.1 MPa or more and 30.0 MPa or less, and more preferably 0.5 MPa or more and 25.0 MPa or less.
The sticking time is not particularly limited, but is preferably 5 seconds or more and 90 minutes or less, and more preferably 30 seconds or more and 10 minutes or less.
By setting the conditions in the pasting process within the above range, the functional layer 3 is pushed into the recess 62 between the adjacent electronic components 4, and the functional layer 3 is used to press the upper surface and the side surface of the electronic component 4 and the side surface thereof. , The upper surface of the substrate 5 exposed from the electronic component 4 can be covered with excellent covering accuracy.

In the functional film 100, as described above, in the release film 1, the upper surface and the side surface of the electronic component 4 and the upper surface of the substrate 5 exposed from the electronic component 4 are covered with the functional layer 3 with excellent coating accuracy. As described above, the functional layer 3 is pushed in following the shape of the recess 62, and functions as a protective (cushioning) material for preventing the pushed functional layer 3 from breaking. Further, the release film 1 is peeled from the functional layer 3 in the next step [2-2].

[2-2] Next, as shown in FIG. 3D, the release film 1 is peeled off from the functional film 100 attached to the electronic component 4.

In the release of the release film 1, peeling occurs at the interface between the release film 1 and the functional layer 3 in the functional film 100, and as a result, the release film 1 is peeled from the functional layer 3. As a result, the upper surface and side surfaces of the electronic component 4 and the upper surface of the substrate 5 exposed from the electronic component 4 are covered with the functional layer 3 in a state where the release film 1 is peeled off from the functional layer 3. The mounting board 50 can be obtained.

The method of peeling the release film 1 is not particularly limited. For example, it can be peeled off manually. In manual peeling, for example, one end of the release film 1 is first gripped, the release film 1 is peeled from the functional layer 3 from the gripped end, and then from this end to the center. Further, the release film 1 is peeled off from the functional layer 3 by sequentially peeling off the release film 1 to the other end portion.

The peeling temperature is preferably 180 ° C. or lower, more preferably 165 ° C. or lower, still more preferably 150 ° C. or lower.

The substrate 5 exposed from the upper surface and side surfaces of the electronic component 4 and the electronic component 4 in a state where the release film 1 is peeled off from the functional layer 3 by going through the steps [2-1] and [2-2]. A functional layer-covered electronic component mounting substrate 50 whose upper surface is covered with the functional layer 3 can be obtained.

[Release film]
The release film (release film 1) of the present embodiment will be described below. As described above, the release film 1 is preferably used as a release film in the functional film 100 used for manufacturing the functional layer-coated electronic component mounting substrate 50.

As shown in FIG. 6, the release film 1 includes a cushion layer 13 and a release layer 11 provided on one surface of the cushion layer 13. The release film 1 preferably has the secondary release layer 12 on the surface of the cushion layer 13 opposite to the side on which the release layer 11 is provided. When the release film 1 is used as a functional film, as shown in FIG. 5, the functional film 100 has a structure in which the functional layer 3 is laminated on the surface of the release layer 11 of the release film 1, in other words. It is preferable that the functional layer 3 / release layer 11 / cushion layer 13 / sub-release layer 12 have a structure in which they are laminated in this order.

When the viscoelasticity of the release film 1 was measured under the conditions of a temperature of 120 ° C., a frequency of 1 Hz, and a twist mode, the storage elastic modulus measured 300 seconds after the start of the measurement was G'[Pa], and the loss tangent was tanδ. When, the value of I defined by the following formula is 3.5 or more.
I = (G'/ 1000000) / tanδ

Based on the studies and findings of the present inventors, the value of the above formula I correlates well with the followability to the unevenness when covering the uneven structure as described above. The correlation between the value of the formula I and the followability can be explained as follows.

The fact that the value of the formula I is 3.5 or more means that the release elastic modulus G'at 120 ° C. of the release film 1 is relatively large and the loss tangent tan δ at 120 ° C. is relatively small. Meaning (120 ° C .: roughly corresponds to the temperature at the time of hot pressing).
The fact that G'at 120 ° C is relatively large and that tan δ at 120 ° C is relatively small (at 120 ° C, elasticity is more predominant than viscosity) is due to heating during hot pressing. This means that the release film 1 does not soften too much and maintains an appropriate rubber elasticity.
Since the release film 1 maintains an appropriate rubber elasticity at the temperature during hot pressing, the release film 1 can maintain its shape to some extent even when it receives an external force (flow is suppressed). It is considered that this makes it difficult for the release film 1 to dissipate the force when the release film 1 is "pushed" into the unevenness when covering the uneven structure. As a result, it is considered that the followability to the unevenness when covering the uneven structure is improved.

By the way, the reason why the values of G'and tan δ of "300 seconds after the start of measurement" are adopted is that the measurement conditions are close to the conditions to which the release film 1 is actually applied (typical). Press conditions: about 2 minutes at about 115 ° C).

The value of the formula I may be 3.5 or more, but from the viewpoint of better followability to unevenness, it is preferably 4 or more, more preferably 5 or more, particularly preferably 5.5 or more, and particularly preferably. 6 or more. There is no particular upper limit to the value of Equation I, but the upper limit is, for example, 30 from the viewpoint of realistic material design and the like.

The value of G'itself at 120 ° C. is, for example, 1.0 × 10 ⁵ to 1.0 × 10 ⁶ [Pa].
The value of tan δ itself at 120 ° C. is, for example, 0.15 to 0.4.
By designing the release film 1 so that G'and tan δ at 120 ° C. fall within the numerical range shown on the left, the above-mentioned "dissipation of force when the release film 1 is pushed into the unevenness" is further suppressed. As a result, it is considered that better followability to unevenness can be obtained.

The release film 1 having the value of the formula I of 3.5 or more can be manufactured by selecting an appropriate material and manufacturing method. The material and manufacturing method of the release film 1 are not limited, but preferably (i) polyethylene and / or polypropylene is used as the material of the cushion layer 13, and (ii) rubber particles are contained in the cushion layer 13. (Iii) Cross-linking the resin in the cushion layer 13 by irradiating with radiation (for example, electron beam), (iv) Making the cushion layer 13 a multi-layer structure, etc. By doing so, the release film 1 having the value of the formula I of 3.5 or more can be manufactured. Details of these will be described later.

Hereinafter, the release film 1 will be described.

(Cushion layer)
The cushion layer 13 preferably contains a polyolefin resin. The cushion layer 13 plays a role of pushing the functional layer 3 so as to follow the shape of the unevenness of the electronic component mounting substrate 45 having the unevenness 6 in the manufacturing process of the electronic component mounting substrate 50 covering the functional layer. That is, the cushion layer 13 makes it possible to obtain the functional film 100 having improved followability (embedding property) to the uneven portion of the functional layer 3.

The polyolefin resin used for the release film 1 is a polymer (including an olefin-based elastomer) composed of an olefin as an essential monomer component, that is, a structure derived from the olefin in the molecule (in one molecule). It is a polymer containing at least a unit. The type of olefin is not particularly limited. For example, α-olefins such as ethylene, propylene, 1-butene and 4-methyl-1-pentene can be mentioned.

As the polyolefin resin, polypropylene resin and / or polyethylene resin are preferably used.

Examples of the polypropylene resin include a propylene homopolymer (homopolypropylene) and a propylene-α-olefin copolymer. Examples of the α-olefin in the propylene-α-olefin copolymer include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and 1-. Examples thereof include α-olefins having 2 to 20 carbon atoms (excluding propylene) such as nonene and 1-decene. As the α-olefin, only one kind may be used, or two or more kinds may be used. The propylene copolymer (propylene-α-olefin copolymer, etc.) may be a block copolymer, a random copolymer, or a graft copolymer.

Examples of the polyethylene resin include ethylene homopolymers and ethylene-α-olefin copolymers. Examples of the polyethylene-based resin include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), medium-density polyethylene (MDPE), and high-density polyethylene (HDPE).
LDPE is, for example, a low-density polyethylene containing a structural unit derived from ethylene as a main component and produced by a high pressure method.
LLDPE is, for example, a low-density polyethylene containing a structural unit derived from ethylene as a main component, produced by a medium-low pressure method, and having a short-chain branch.

Examples of the α-olefin in the ethylene-α-olefin copolymer include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and 1-nonene. , 1-decene and the like α-olefins having 3 to 20 carbon atoms (preferably 1-butene, 1-pentene, 1-hexene, 1-octene, more preferably 1-pentene, 1-hexene, 1-octene) and the like. Can be mentioned. As the α-olefin, only one kind may be used, or two or more kinds may be used.

In a preferred embodiment, the cushion layer 13 contains both a polypropylene resin and a polyethylene resin. As a result, the value of the formula I tends to be 3.5 or more, and more appropriate pushability and unevenness followability can be exhibited. When the cushion layer 13 contains the polypropylene resin and the polyethylene resin, the blending ratio of the polypropylene resin and the polyethylene resin is a mass ratio of polypropylene resin: polyethylene resin, for example, 20:80 to 80:20, preferably 30. : 70 to 70:30, more preferably 40:60 to 60:40.

The cushion layer 13 may contain a polyolefin resin other than the above-mentioned resin. Examples of such resins include ethylene-propylene-rubber (EPR), ethylene-propylene-diene rubber (EPDM), thermoplastic olefin-based elastomer (TPO), ethylene-vinyl acetate copolymer, and ethylene-acrylic acid copolymer. Examples thereof include a coalescence, an ethylene- (meth) alkyl acrylate copolymer, and a modified copolymer obtained by copolymerizing these with maleic anhydride.

As one aspect, the cushion layer 13 preferably contains rubber particles. As a result, the value of the formula I tends to be 3.5 or more, and more appropriate pushability and unevenness followability can be exhibited. The rubber particles have a function of maintaining a high elastic modulus of the cushion layer 13 under heating and imparting flexibility and toughness to the cushion layer 13.

The rubber particles preferably include (meth) acrylic rubber, butadiene rubber, or silicone / acrylic rubber. These may be used alone or in combination of two or more.

The rubber particles are graft copolymers containing a rubber-like polymer (crosslinked polymer), that is, core-shell type rubber particles having a core portion made of a rubber-like polymer (crosslinked polymer) and a shell portion covering the core portion. Is preferable.

Examples of the rubber-like polymer include a butadiene-based crosslinked polymer, a (meth) acrylic-based crosslinked polymer, and an organosiloxane-based crosslinked polymer. Among them, a (meth) acrylic crosslinked polymer is preferable, and an acrylic crosslinked polymer (acrylic rubber-like polymer) is more preferable, from the viewpoint that the transparency of the obtained cushion layer is not easily impaired.

That is, it is preferably an acrylic graft copolymer containing an acrylic rubber-like polymer. The acrylic graft copolymer containing the acrylic rubber-like polymer is preferably core-shell type particles having a core portion containing the acrylic rubber-like polymer and a shell portion covering the core portion. Such core-shell type particles are a multi-stage polymer obtained by polymerizing at least one stage or more of a monomer mixture containing a methacrylic acid ester as a main component in the presence of an acrylic rubber-like polymer. The polymerization can be carried out by an emulsification polymerization method. The polymer of the monomer mixture constituting the shell portion is a graft component for the acrylic rubber-like polymer. The monomer mixture preferably contains a methacrylic acid ester as a main component.

The average particle size of the rubber particles is preferably 100 to 700 nm, more preferably 300 to 600 nm. When the average particle size is 100 nm or more, the cushion layer 13 may have an elastic modulus appropriate for exhibiting the pushability to the functional layer 3, and when it is 700 nm or less, the transparency of the cushion layer 13 decreases. Hateful.

The average particle size of the rubber particles is specified as an average value of the equivalent circle diameters of 100 particles obtained by SEM or TEM photography of the film surface and sections. The equivalent circle diameter can be obtained by converting the projected area of the particles obtained by photographing into the diameter of a circle having the same area. At this time, the rubber particles (acrylic graft copolymer) observed by SEM observation and / or TEM observation at a magnification of 5000 times are used for calculating the average particle size. The average particle size of the rubber particles (acrylic graft copolymer) in the dispersion can be measured by a zeta potential / particle size measurement system (ELSZ-2000ZS manufactured by Otsuka Electronics Co., Ltd.).

The content of the rubber particles is, for example, 1 to 20% by mass, preferably 3 to 18% by mass, and more preferably 5 to 15% by mass with respect to the entire cushion layer 13. By using the rubber particles with a content within the above range, the cushion layer 13 obtained has an appropriate elastic modulus, has relatively few irregularities due to the rubber particles, and has a certain degree of transparency.

As one aspect, the cushion layer 13 preferably contains a crosslinked polyolefin resin. It is considered that this is because the crosslinked polyolefin resin has a high crosslink density and thus maintains a high elastic modulus at high temperatures.

The crosslinked polyolefin resin is prepared by mixing an uncrosslinked polyolefin resin with, for example, (i) a method of irradiating radiation (electron beam or the like), (ii) a polyethylene organic silane compound, and allowing water to permeate in the presence of a catalyst. It can be obtained by cross-linking by a known or conventional method such as a method of cross-linking with (iii) a method of mixing and heating a cross-linking agent (organic peroxide or the like). In the present embodiment, the crosslinked polyolefin resin is preferably (i) a polyolefin resin crosslinked by radiation (electron beam or the like) from the viewpoint of good workability.
Here, examples of the "uncrosslinked polyolefin resin" include the above-mentioned polypropylene resin and polyethylene resin.

As one aspect, the cushion layer 13 may be composed of two or more layers. Of course, the cushion layer 13 may be a single layer as long as the value of the formula I is 3.5 or more.

From the viewpoint of further enhancing the effect of following the unevenness, the cushion layer 13 is on the opposite side of the first cushion layer in contact with the release layer 11 and the surface of the first cushion layer on the release layer 11 side. It is preferable to include 2 cushion layers. When the mass ratio of polyethylene in the total resin contained in the first cushion layer is p1, and the mass ratio of polyethylene in the total resin contained in the second cushion layer is p2, it is preferable that p1> p2.
Similarly, the cushion layer 13 includes a first cushion layer in contact with the release layer 11, a second cushion layer on the side opposite to the surface of the first cushion layer on the release layer 11 side, and a second cushion layer. It is preferable to include a third cushion layer on the side opposite to the surface on the one cushion layer side. Then, the mass ratio of polyethylene in the total resin contained in the first cushion layer is p1, the mass ratio of polyethylene in the total resin contained in the second cushion layer is p2, and the mass ratio of polyethylene in the total resin contained in the third cushion layer is p2. When the mass ratio is p3, it is preferable that p1>p2> p3.
Incidentally, when a part of the resin contained in the first cushion layer is polyethylene, the rest of the resin contained in the first cushion layer is, for example, polypropylene. The same applies to the second cushion layer.

p1> p2 or p1>p2> p3, that is, the mass ratio of polyethylene on the release layer 11 side in the cushion layer 13 is large, and the mass of polyethylene on the secondary release layer 12 side in the cushion layer 13 is large. The reason why a small ratio is preferable can be explained as follows.
As a general tendency, when the mass ratio of the polyethylene resin in the cushion layer 13 is large, G'at 120 ° C. is small, and when the mass ratio of the polyester resin in the cushion layer is small, G'at 120 ° C. is large. For example, when the cushion layer 13 has a two-layer structure and p1> p2, (the storage elastic modulus of the first cushion layer at 120 ° C.) <(the storage elastic modulus of the second cushion layer at 120 ° C.). It is considered to be.
When the release film 1 is used, pressure is applied from the side of the second cushion layer or the third cushion layer (from the side of the secondary release layer 12, if any). Therefore, in terms of "suppressing the dissipation of force when the release film 1 is pushed into the unevenness", the force is increased because the second cushion layer or the third cushion layer, in which the pressure is transmitted more directly, is harder. Dissipation is considered to be further suppressed.
In addition, the second cushion layer or the third cushion layer has a relatively large G'at 120 ° C. and is difficult to plastically deform, while the first cushion layer has a relatively small G'at 120 ° C. and the second cushion layer or the second cushion layer. 3 It is considered that the fact that it is more easily plastically deformed than the cushion layer is also related to the further improvement of the followability to unevenness.

When the cushion layer 13 includes the first cushion layer and the second cushion layer, the value of p1-p2 is, for example, 5 to 30% by mass, preferably 5 to 25% by mass. Further, the value of p1 itself is, for example, 30 to 50% by mass, and the value of p2 itself is, for example, 10 to 40% by mass.
When the cushion layer 13 includes the first cushion layer, the second cushion layer, and the third cushion layer, the value of p1-p2 is, for example, 5 to 15% by mass, and the value of p2-p3 is, for example, 5 to 15% by mass. %. Further, the value of p1 itself is, for example, 30 to 50% by mass, the value of p2 itself is, for example, 20 to 40% by mass, and the value of p3 itself is, for example, 10 to 30% by mass.

When the cushion layer 13 includes the first cushion layer and the second cushion layer, the thickness ratio thereof is, for example, the first cushion layer: the second cushion layer = 10: 90 to 90:10, specifically, The first cushion layer: the second cushion layer = 15:85 to 85:15.
When the cushion layer 13 includes the first cushion layer, the second cushion layer, and the third cushion layer, the thickness ratio is, for example, the first cushion layer: the second cushion layer: the third cushion layer = 10: 45 :. 45 to 96: 2: 2, specifically, the first cushion layer: the second cushion layer: the third cushion layer = 30:35:35 to 90: 5: 5.

(Release layer)
As shown in FIG. 5, the release layer 11 is laminated on one surface of the cushion layer 13. When the release film 1 is used as the material of the functional film 100, the functional layer 3 is laminated on the surface of the release layer 11. The release layer 11 is a layer having a release property with respect to the functional layer 3.

The release layer 11 preferably contains a polyolefin resin. Examples of the polyolefin resin used for the release layer 11 include linear high-density polyethylene, linear low-density polyethylene, high-pressure low-density polyethylene, isotactic polypropylene, syndiotactic polypropylene, block polypropylene, and random polypropylene. Examples thereof include polybutene, 1,2-polybutadiene, 4-methylpentene, cyclic polyolefins and copolymers thereof (for example, ethylene-methyl methacrylic acid copolymer and the like).

The release layer 11 may contain additives such as antistatic agents, process oils, plasticizers, mold release agents, pigments and the like, if necessary. Further, the outer surface of the release layer 11 (the surface on which the functional layer 3 is laminated) may be subjected to a release treatment such as application of a release agent or heat treatment for the purpose of improving the release property.

(Secondary mold release layer)
As shown in FIG. 5, the sub-release layer 12 is laminated on the surface of the cushion layer 13 opposite to the surface on which the release layer 11 is laminated, if necessary. When the release film 1 is used as the material of the functional film 100, it is press-molded on the secondary release layer 12 in the step of attaching the functional film 100 using the above-mentioned press molding method [2-1]. Cushion material is placed.

The secondary release layer 12 preferably contains a polyolefin resin. Specific examples of the polyolefin include the polyolefin exemplified as the material constituting the release layer 11. The release layer 11 and the sub-release layer 12 may contain the same polyolefin resin or may contain different polyolefin resins.

The secondary mold release layer 12 may contain, for example, an antistatic agent, a process oil, a plasticizer, a mold release agent, a pigment, or the like, if necessary. Further, the outer surface of the secondary mold release layer 12 (the surface opposite to the surface on which the cushion layer 13 is laminated) is subjected to a mold release treatment such as application of a mold release agent or heat treatment for the purpose of improving the mold release property. It may be given.

As an example, the secondary release layer 12 preferably contains inorganic particles such as silica and aluminosilicate (zeolite). The inorganic particles function, for example, as an anti-blocking agent. When inorganic particles are used, the amount thereof is, for example, 5 to 30% by mass, preferably 10 to 20% by mass in the secondary release layer 12.

(Other layers)
The release film (release film 1) of the present embodiment may include a layer other than the cushion layer, the release layer, and the secondary release layer. This layer can be placed at any position.

(Thickness of each layer)
In the release film 1, the thickness of the cushion layer 13 is, for example, 50 to 400 μm, preferably 100 to 350 μm, and more preferably 150 to 300 μm. When the release film 1 including the cushion layer 13 is used as the release film of the functional film 100, the pushability to the functional layer 3 is improved because the thickness of the cushion layer 13 is within the above range. It is possible to obtain a functional film 100 having excellent followability.

The thickness of the release layer 11 is, for example, 5 to 100 μm, preferably 15 to 80 μm, and more preferably 30 to 60 μm. When the release film 1 is used as the release film of the functional film 100 because the thickness of the release layer 11 is within the above range, the releaseability and functionality of the release film 1 at the time of release. It is possible to achieve both the ability to follow the unevenness of the film.

The thickness of the secondary release layer 12 is, for example, 5 to 100 μm, preferably 15 to 80 μm, and more preferably 30 to 60 μm. The secondary release layer 12 having a thickness within the above range is for press molding, which is arranged on the secondary release layer 12 in the application step [2-1] of the functional film 100 using the above press molding method. Has good mold releasability with respect to the cushioning material of.

The thickness of the entire release film 1 can be, for example, 100 to 500 μm.

(Relationship between each layer)
In the release film 1, the mass ratio of polyethylene in the total resin contained in the cushion layer 13 is P1, the mass ratio of polyethylene in the total resin contained in the release layer 11 is P2, and the mass ratio of polyethylene in the secondary release layer 12 is all resin. When the mass ratio of polyethylene in the film is P3, it is preferable that P1> P2 and P1> P3.
When the release film 1 is used, pressure is applied from the side of the secondary release layer 12. P1> P3, that is, the cushion layer 13 contains more polyethylene having a relatively low melting point than the secondary release layer 12, so that the secondary release layer 12 is “harder” at 120 ° C. and the cushion layer. 13 is considered to be "softer". In terms of suppressing the dissipation of force when the release film 1 is pushed into the unevenness, it is considered that the dissipation of force is further suppressed because the secondary release layer 12 to which the pressure is directly transmitted is harder.
Further, since P1> P2, the cushion layer 13 can be sufficiently deformed while suppressing the tackiness of the material of the release layer 11, so that the releaseability after the release film 1 is used is improved. Can be done.

The value of P1-P2 is, for example, 1 to 50% by mass, specifically 5 to 40% by mass.
The value of P1-P3 is, for example, 1 to 50% by mass, specifically 5 to 40% by mass.
The value of P1 itself is, for example, 20 to 50% by mass, specifically 25 to 50% by mass.
The value of P2 itself is, for example, 0 to 30% by mass, specifically 0 to 20% by mass.
The value of P3 itself is, for example, 0 to 30% by mass, specifically 0 to 20% by mass.

[Manufacturing method of release film]
The release film 1 can be manufactured, for example, by a coextrusion method. Specifically, it is molded by a resin melt extrusion method such as a tubular method, an inflation method, or a T-die method. More specifically, the release film 1 is prepared by, for example, using a plurality of extruders set to predetermined temperatures to form a release layer, a cushion layer, and, if necessary, a secondary release layer. Each is charged and manufactured by co-extruding a laminated structure containing a raw material for a release layer, a raw material for a cushion layer, and a raw material for a secondary release layer in this order from a co-extruder.

The co-extruded laminated structure is usually cooled by using a cooling drum or the like. Although the cooling method is not limited, it is preferable to cool the resin under conditions close to quenching or quenching (for example, a water cooling method) because crystallization of the resin is suppressed and transparency is improved. Therefore, the cooling temperature is preferably 0 to 70 ° C, more preferably 10 to 60 ° C.

When the cushion layer 13 is crosslinked, the method can be performed by a known or conventional method such as the above-mentioned methods (i) to (iii). When the cushion layer is crosslinked by irradiation, radiation is applied to the release layer side, the sub-release layer side, or both sides of the obtained laminated structure. Examples of radiation include α-rays, β-rays, electron-rays, γ-rays, and X-rays. Among them, electron beams and γ-rays are preferable, and electron beams are more preferable, from the viewpoint of large cross-linking effect before and after irradiation.

When irradiating an electron beam as radiation, the acceleration voltage is preferably 150 to 500 kV. The irradiation dose is preferably 50 to 200 kilogray (kGy). When the acceleration voltage and / or the irradiation dose is equal to or higher than the above lower limit value, the cross-linking of the polyolefin resin in the cushion layer proceeds sufficiently. When the acceleration voltage and / or the irradiation dose is not more than the above upper limit value, the decomposition of the resin contained in the release layer or the secondary release layer can be further suppressed.

[Manufacturing method of functional film]
The functional film 100 of the present embodiment is produced by laminating a functional layer 3 prepared in advance on a release film 1 by an extrusion laminating method, or by dry laminating the functional layer 3 prepared in advance. Can be done.

The thickness of the functional layer 3 is, for example, 3 to 300 μm. When the thickness of the functional layer 3 is within the above range, the function can be fully exhibited.

The thickness of the entire functional film 100 can be, for example, 100 to 800 μm.

Although the embodiments of the present invention have been described above, these are examples of the present invention, and various configurations other than the above can be adopted. Further, the present invention is not limited to the above-described embodiment, and modifications, improvements, and the like to the extent that the object of the present invention can be achieved are included in the present invention.

Embodiments of the present invention will be described in detail based on Examples and Comparative Examples. As a reminder, the invention is not limited to examples.

<Manufacturing of mold release film>
(Manufacturing of mold release film in which the cushion layer contains rubber particles)
-Examples 1 to 4
Random polypropylene (manufactured by Sumitomo Chemical Co., Ltd., S131) 100% by mass was used as a raw material constituting the release layer.
Random polypropylene (manufactured by Japan Polypropylene Corporation, EG7FTB) 40% by mass, low density polyethylene (density: 0.928 g / cm ³ , manufactured by Japan Polyethylene Corporation, LF280H) 60% by mass, and rubber particles are used as raw materials constituting the cushion layer. (Average particle size: 500 μm, manufactured by Mitsubishi Chemical Corporation, W-450A) was used. The rubber particles were used in the blending amount shown in Table 1 (mass% with respect to the total amount of random polypropylene and low-density polyethylene).
Random polypropylene (manufactured by Sumitomo Chemical Co., Ltd., S131) 85% by mass and silica (manufactured by Nittetsu Chemical & Materials Co., Ltd., product name: SC10-32F) 15% by mass were used as raw materials constituting the secondary release layer.
Using the raw materials for each layer prepared above, a laminate was formed by a coextrusion method using a feed block and a multi-manifold die, and the total thickness was 350 μm (thickness ratio: release layer / cushion layer / secondary release layer). A release film was produced as a coextruded film having a laminated structure of = 1 / 5.5 / 1). At this time, the temperature of the multi-manifold die was 250 ° C. and the temperature of the cooling drum was 40 ° C.

-Comparative example 1
A release film was produced in the same manner as in Example 1 except that rubber particles were not used.

(Manufacturing of a release film containing a polyolefin resin having a crosslinked cushion layer)
-Examples 2-1 to 2-10
Random polypropylene (manufactured by Sumitomo Chemical Co., Ltd., S131) 100% by mass was used as a raw material constituting the release layer.
As raw materials constituting the cushion layer, 40% by mass of random polypropylene (manufactured by Japan Polypropylene Corporation, EG7FTB) and 60% by mass of low density polyethylene (density: 0.928 g / cm ³ , manufactured by Japan Polyethylene Corporation, LF280H) were used.
Random polypropylene (manufactured by Sumitomo Chemical Co., Ltd., S131) 85% by mass and silica (manufactured by Nittetsu Chemical & Materials Co., Ltd., product name: SC10-32F) 15% by mass were used as raw materials constituting the secondary release layer.
Using the raw materials for each layer prepared above, a laminate was formed by a coextrusion method using a feed block and a multi-manifold die. With the acceleration voltage and irradiation dose shown in Table 2 below, low-density polyethylene was crosslinked by electron beam irradiation from the release layer side, the secondary release layer side, or both sides, and the total thickness was 350 μm (thickness ratio:: A release film was produced as a coextruded film having a laminated structure of a release layer / cushion layer / sub-release layer = 1 / 5.5 / 1). At this time, the temperature of the multi-manifold die was 250 ° C. and the temperature of the cooling drum was 40 ° C.

-Comparative Example 2-1
A release film was produced in the same manner as in Example 2-1 except that electron beam irradiation was not performed.

(Manufacturing a release film with a multi-layered cushion layer)
-Example 3-1
First, the following were prepared as materials for each layer.
Release layer: Random polypropylene (manufactured by Sumitomo Chemical Co., Ltd., S131) 100% by mass
Cushion layer: As the first cushion layer, a mixture of polypropylene (i) and polyethylene (ii) at a mass ratio of 60:40 was prepared. As the second cushion layer, a mixture of polypropylene (i) and polyethylene (ii) at a mass ratio of 70:30 was prepared.
(I) Random polypropylene manufactured by Japan Polypropylene Corporation, trade name: Novatec PP, grade: EG7FTB
(Ii) Low-density polyethylene manufactured by Japan Polyethylene Corporation, trade name: Novatec LD, grade: LF280H
Sub-release layer: Random polypropylene (manufactured by Sumitomo Chemical Co., Ltd., S131) 85% by mass, and silica (manufactured by Nittetsu Chemical & Materials Co., Ltd., product name: SC10-32F) 15% by mass.

Using the raw materials for each layer prepared above, a laminate was formed by a coextrusion method using a feed block and a multi-manifold die. Then, as a release film as a coextruded film having a laminated structure having a total thickness of 350 μm (thickness ratio: release layer / cushion layer (total in the case of multiple layers) / sub-release layer = 1 / 5.5 / 1). Was produced. At this time, the temperature of the multi-manifold die was 250 ° C. and the temperature of the cooling drum was 40 ° C.

-Examples 3-2 to 3-7 and Comparative Example 3-1
A release film was produced in the same manner as in Example 3-1 except that the configurations of the cushion layer and the secondary release layer were as shown in Table 3.

<Measurement of viscoelasticity of release film>
Using the viscoelasticity measuring device "MCR301" manufactured by AntonioPaar, the viscoelasticity was measured in the twist mode with the following settings. Then, the storage elastic modulus G'[Pa] and the loss tangent tan δ measured 300 seconds after the start of the measurement were obtained.
-Distance between gaps: Film thickness minus 0.03 to 0.05 mm (set so that the normal force is 0.5 to 1N)
・ Temperature: 120 ℃
・ Frequency: 1Hz
-Sample: The release film produced in the above Example or Comparative Example was cut into pieces of about 4 cm x 4 cm.
・ Gamma (degree of twist): initial 1%, end point 0.1%

<Manufacturing of functional film>
As a resin material (liquid material) for forming a functional layer, 22 parts by weight of epoxy resin (manufactured by DIC, trade name: EPICRON N-670) and acrylic rubber (manufactured by Nagase Chemtex, trade name: SG-708) are used. A solution containing 22 parts by weight of -6), 11 parts by weight of a phenol novolac resin (manufactured by Sumitomo Bakelite Co., Ltd., trade name: PR-HF-3) and further containing methyl ethyl ketone as a solvent was prepared. A functional layer (thickness: 50 μm) was produced by applying a resin material on the released mold release PET between the delivery roller and the take-up roller and then drying the material.
A functional layer is dry-laminated on the release films of the above-mentioned Examples and Comparative Examples, and then the release PET is peeled off to obtain a functional film having a structure in which the release film and the functional layer are laminated. Obtained.

<Manufacturing of electronic component mounting boards with recesses>
In order to obtain an electronic component mounting substrate 45 provided with a recess 62, first, a FR4 substrate (a pseudo-wiring board formed by sealing a glass fiber cloth with a cured product of an epoxy resin) is 5 mm long × horizontal. An electronic component mounting substrate 45 was obtained by arranging 10 mm × 0.8 mm thick Si substrates (pseudo-electronic components) in a grid pattern so that the separation distance between adjacent Si substrates was 0.2 mm.

<Performance evaluation of functional film>
(1. Releasability)
The releasability of the release film in the functional films obtained in each Example and Comparative Example was evaluated by the following method.
A release film with a functional film is placed on an electronic component mounting substrate 45 provided with a recess 62 so that the longitudinal direction of the release film is parallel to the longitudinal direction of the electronic component mounting substrate 45 and the functional film. Was arranged so as to be in contact with the electronic component mounting board 45.
Next, using a vacuum press machine (KVHCIII manufactured by Kitagawa Seiki Co., Ltd.), the functional film is pressed under the conditions of a pressure of 13 MPa (execution pressure on the electronic component mounting substrate 45), a temperature of 115 ° C., and a time of 180 seconds to press the functional film into electronic components. By attaching to the mounting board 45, the functional layer provided in the functional film was pushed in so as to correspond to the shape of the recess 62 provided in the electronic component mounting board 45.
Next, the release film was peeled off from the functional film attached to the electronic component mounting substrate 45 by holding one end of the release film.
The appearance of the functional layer after the release film was peeled off was visually observed, and the results were evaluated based on the evaluation criteria shown below. The evaluation results are shown in each table.
[Evaluation criteria]
⊚: No roughness is observed in the appearance of the functional layer coated on the electronic component mounting board.
◯: A slight roughness is observed in the appearance of the functional layer covered with the electronic component mounting board.
X: Clear roughness is observed in the appearance of the functional layer coated on the electronic component mounting substrate.

(2. Followability 1 (followability to the bottom))
The followability of the functional films obtained in each Example and Comparative Example to the uneven portion of the electronic component mounting substrate was evaluated by measuring the defect height of the functional layer.
The defect height was measured by the following method.
The release film was peeled off from the functional film attached to the electronic component mounting substrate 45 by holding one end of the release film in the same manner as described in the above-mentioned evaluation of “1. Releasability”. Then, with respect to the functional layer pushed in so as to correspond to the shape of the recess 62, the coating accuracy of the bottom of the recess 62 was visually observed, and the result was evaluated based on the evaluation criteria shown below. The evaluation results are shown in each table.
[Evaluation criteria]
◎ ◎: The functional layer can be covered up to the bottom of the recess 62, and no protrusion due to floating of the functional layer from the bottom of the recess 62 is observed.
⊚: The functional layer can be covered up to the bottom of the recess 62, but a very small protrusion of the functional layer is observed around the cross portion 63.
◯: The functional layer can be covered up to the bottom of the recess 62, but small protrusions of the functional layer are observed around the cross portion 63.
X: The functional layer can be covered up to the bottom of the concave portion 62, but a clear protrusion due to the floating of the functional layer from the bottom of the concave portion 62 is observed in the peripheral portion of the cross portion 63.

(3. Followability 2 (followability to the wall surface))
In the same manner as in the method described in "2. Followability 1" described above, the release film was peeled off from the functional film attached to the electronic component mounting substrate 45 by holding one end of the release film. Then, in order to evaluate the covering accuracy of the side surface (wall surface) of the convex portion 61, it was cut and fragmented along the concave portion 62 using a dicer. The covering defect of the side surface (wall surface) of the convex portion 61 after being individualized was measured using a microscope. The measurement results are shown in each table.

The functional film of the example was excellent in both the releasability of the release film and the followability of the functional layer to the uneven portion of the electronic component mounting substrate.

1 Release film 3 Functional layer 4 Electronic component 5 Board 6 Concavo-convex 11 Detachable layer 12 Sub-separation layer 13 Cushion layer 45 Electronic component mounting board 50 Functional layer Covered electronic component mounting board 61 Convex part 62 Concave 63 Cross part 100 Functionality the film

Claims (10)

A release film comprising a cushion layer and a release layer laminated on one surface of the cushion layer.
When the viscoelasticity of the release film was measured under the conditions of a temperature of 120 ° C., a frequency of 1 Hz, and a twist mode, the storage elastic modulus measured 300 seconds after the start of measurement was G'[Pa], and the loss positive contact was tanδ. When the value of I defined in the following formula is 3.5 or more, the release film.
I = (G'/ 1000000) / tanδ The release film according to claim 1.
The cushion layer is a release film containing a polyolefin resin. The release film according to claim 2.
The polyolefin resin is a release film containing 1 or 2 or more selected from the group consisting of polypropylene and polyethylene. The release film according to any one of claims 1 to 3.
The cushion layer is a release film containing rubber particles. The release film according to any one of claims 1 to 4.
The cushion layer is a release film containing a crosslinked polyolefin resin. The release film according to any one of claims 1 to 5.
A release film further comprising a secondary release layer laminated on a surface of the cushion layer opposite to the surface on which the release layer is laminated. The release film according to claim 6.
The secondary release layer is a release film containing a polyolefin resin. The release film according to any one of claims 1 to 7.
The release layer is a release film containing a polyolefin resin. The release film according to claim 6 or 7.
The mass ratio of polyethylene in the total resin contained in the cushion layer is P1.
The mass ratio of polyethylene in the total resin contained in the release layer is P2.
When the mass ratio of polyethylene in the total resin contained in the secondary release layer is P3,
A release film in which P1> P2 and P1> P3. The release film according to any one of claims 1 to 9, and the release film.
A functional film comprising a functional layer laminated on the release layer of the release film.

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