Multilayer sheet and method for producing laminate

Abstract

This invention prevents the occurrence of peeling failure during lamination processing using a multilayer sheet. A multilayer sheet 100 is formed by laminating a first base material film 12, an adhesive film 14, a second base material film 16, and a third base material film 18 in this order, and satisfies the following formula (1). Formula (1): P1 < P2 < P3 [In the formula, P1 represents a peel strength between the first base material film and the adhesive film, P2 represents a peel strength between the adhesive film and the second base material film, and P3 represents a peel strength between the second base material film and the third base material film.]

Description

Method for manufacturing multilayer sheet and laminate

[0001] The present invention relates to a method for producing a multilayer sheet and a laminate.

[0002] In the manufacturing process of various products such as semiconductor devices, a lamination process is sometimes carried out using a multilayer sheet consisting of an adhesive film and one or more other films (hereinafter referred to as "substrate films") provided on both sides of the adhesive film (see, for example, Patent Document 1). The lamination process usually includes the following first step (first substrate film peeling step) and second step (laminate formation step): (1) the first step of peeling off the substrate film (first substrate film) provided on one side of the multilayer sheet to expose one side of the adhesive film; and (2) the second step of bonding a member to be laminated (e.g., a semiconductor wafer) to the exposed surface of the adhesive film and applying heat and pressure to obtain a laminate.

[0003] Japanese Patent Application Laid-Open No. 2022-2231

[0004] In performing the lamination process, from the viewpoints of product production efficiency, manufacturing costs, etc., it may be preferable to perform the half-cutting step described below prior to performing the first step, and to perform the second region peeling step described below after performing the half-cutting step and before or simultaneously with performing the first step. (P1) A half-cutting step in which one surface of the multilayer sheet is partially cut (half-cut) halfway through the thickness of the multilayer sheet so as to also cut the adhesive film, thereby dividing the one surface into a first region (e.g., a circular region) and a second region (a region other than the first region) using the cutting line formed by the cutting as a boundary line. (P2) A second region peeling step in which the second region formed on one surface of the multilayer sheet is selectively peeled (removed) from the multilayer sheet so as to include the adhesive film layer. When these steps are performed, the first and second steps are performed on the first region.

[0005] On the other hand, a multilayer sheet having a (first) substrate film, an adhesive film, and a (second) substrate film laminated in this order has a simple three-layer structure and is a typical and representative type of multilayer sheet used in lamination. The inventors have confirmed that, when using the above-described three-layer multilayer sheet in a lamination process including the half-cutting process and the second region peeling process, one or both of the following two types of peeling defects occur simultaneously: (D1) In the first step, in the first region, the adhesive film (which should not be peeled) peels off together with the substrate film (first substrate film) on one side (excessive peeling); (D2) In the second region peeling step, in the second region, part or all of the adhesive film (which should be peeled together with the substrate film (first substrate film) on one side) remains attached to the substrate film (second substrate film) on the other side (insufficient peeling).

[0006] The present invention has been made in consideration of the above circumstances, and aims to provide a multilayer sheet that can suppress the occurrence of the two types of peeling defects mentioned above in a lamination process that includes a half-cutting process in which one surface is divided into a first region and a second region by half-cutting, and a second region peeling process in which the second region is selectively peeled from the multilayer sheet so as to also include the adhesive film layer, and a method for manufacturing a laminate using the same.

[0007] The above object is achieved by the present invention as follows. That is, the multilayer sheet of the present invention comprises a first base film, an adhesive film, a second base film, and a third base film, wherein the first base film, the adhesive film, the second base film, and the third base film are laminated in this order, and satisfies the following formula (1): Formula (1) P1<P2<P3 (In formula (1), P1 represents the peel strength (N / 250 mm) between the first base film and the adhesive film, P2 represents the peel strength (N / 250 mm) between the adhesive film and the second base film, and P3 represents the peel strength (N / 250 mm) between the second base film and the third base film.)

[0008] In one embodiment of the multilayer sheet of the present invention, it is preferable that the following formula (2) is satisfied: Q2 / Q3≦2.0 (in formula (2), Q2 represents the modulus of elasticity (MPa) of the second base film, and Q3 represents the modulus of elasticity (MPa) of the third base film).

[0009] In another embodiment of the multilayer sheet of the present invention, the peel strength P3 is preferably 0.5 N / 250 mm to 15 N / 250 mm.

[0010] In another embodiment of the multilayer sheet of the present invention, the peel strength P2 is preferably greater than 0.1 N / 250 mm and equal to or less than 5 N / 250 mm.

[0011] In another embodiment of the multilayer sheet of the present invention, the peel strength P1 is preferably 0.1 N / 250 mm or more and less than 5 N / 250 mm.

[0012] In another embodiment of the multilayer sheet of the present invention, the third base film preferably comprises a PET film and a pressure-sensitive adhesive layer provided on at least one surface of the PET film.

[0013] In another embodiment of the multilayer sheet of the present invention, it is preferable that the second base film has a release-treated surface on the side that comes into close contact with the adhesive film.

[0014] In another embodiment of the multilayer sheet of the present invention, the adhesive film is preferably made of a resin composition containing an epoxy resin, a curing agent, an inorganic filler, and a black pigment.

[0015] In another embodiment of the multilayer sheet of the present invention, it is preferable that the first base film has a release-treated surface on the side that comes into close contact with the adhesive film.

[0016] Another embodiment of the multilayer sheet of the present invention is preferably used in the manufacture of semiconductor devices.

[0017] The method for producing a laminate of the present invention includes a half-cutting step of partially cutting the multilayer sheet of the present invention from the surface of the multilayer sheet on which the first base film is provided halfway through the thickness direction of the multilayer sheet so as to separate the first base film, the adhesive film, and the second base film, and simultaneously dividing the surface of the multilayer sheet on which the first base film is provided into a first region and a second region other than the first region, using a cutting line formed by the cutting as a boundary line; and a second region peeling step of peeling the second region at an interface between the second base film and the third base film. It is preferable that the method includes a first step of peeling the first region at the interface between the first base film and the adhesive film, and a second step of forming a laminate by heating and pressurizing a laminate obtained by attaching a member to be laminated to the surface of the adhesive film of a sheet main body portion in which the second base film and the adhesive film are laminated in this order on one side of the third base film and in the first region, which is one of two sheets obtained by separating the multilayer sheet into two in its thickness direction by at least going through the second region peeling step and the first step.

[0018] In one embodiment of the method for producing a laminate of the present invention, the first step is preferably carried out after the second region peeling step is carried out.

[0019] In another embodiment of the method for producing a laminate of the present invention, the second region peeling step and the first step are preferably carried out substantially simultaneously.

[0020] In another embodiment of the method for producing a laminate of the present invention, the multilayer sheet is preferably a strip-shaped sheet.

[0021] In another embodiment of the method for producing a laminate of the present invention, the first region is preferably a plurality of circular regions or substantially circular regions arranged along the longitudinal direction of the multilayer sheet.

[0022] In another embodiment of the method for producing a laminate according to the present invention, the member to be laminated is preferably a semiconductor wafer or a glass wafer.

[0023] According to the present invention, it is possible to provide a multilayer sheet that can suppress the occurrence of the two types of peeling defects described above in a lamination process that includes a half-cutting process in which one surface is divided into a first region and a second region by half-cutting, and a second region peeling process in which the second region is selectively peeled from the multilayer sheet so as to also include the adhesive film layer, and a method for manufacturing a laminate using the same.

[0024] 3(a) is a schematic diagram illustrating an example of a lamination process using a multilayer sheet; FIG. 3(b) is a cross-sectional view showing an example of the cross-sectional structure of a multilayer sheet of this embodiment; FIG. 3(c) is a schematic diagram showing an example of a multilayer sheet after half-cutting in a lamination process (first process and second process) using a multilayer sheet of this embodiment; FIG. 3(a) is a plan view showing an example of a multilayer sheet after half-cutting as viewed from the half-cut surface side, and FIG. 3(b) is a cross-sectional view taken along the line A-A in FIG. 3(a). FIG. 3(c) is a plan view showing an example of a state in which a release tape is attached to the half-cut surface of a multilayer sheet after half-cutting in a lamination process (first process) using a multilayer sheet of this embodiment; FIG. 5(a) is a cross-sectional view showing a state in which a multilayer sheet is separated into a sheet main body portion and an unnecessary sheet portion in a lamination process (first process) using a multilayer sheet of this embodiment; FIG. 5(b) is a cross-sectional view of the sheet main body portion, and FIG. 5(b) is a cross-sectional view of the unnecessary sheet portion. 6(a) is a cross-sectional view showing a state in which a multilayer sheet is separated into a sheet main body portion and an unnecessary sheet portion in a lamination process (second process) using the multilayer sheet of this embodiment. Here, FIG. 6(a) is a cross-sectional view of the sheet main body portion, and FIG. 6(b) is a cross-sectional view of the unnecessary sheet portion. Here, FIG. 6(a) is a plan view showing an example of a state in which a release tape is attached to the half-cut surface of the sheet main body portion shown in FIG. 6(a) in a lamination process (second process) using the multilayer sheet of this embodiment. Here, FIG. 6(b) is a cross-sectional view showing the sheet main body portion after the first step (first substrate film peeling step) is performed on the sheet main body portion shown in FIG. 7 in a lamination process (second process) using the multilayer sheet of this embodiment. Here, FIG. 10(a) is a plan view showing an example of a multilayer sheet after half-cutting, as viewed from the half-cut surface side, and FIG. 10(b) is a cross-sectional view taken along the line B-B in FIG. 10(a).12(a) is a cross-sectional view showing a state in which a multilayer sheet is separated into a main sheet portion and an unnecessary sheet portion in a conventional lamination process (first process) using a multilayer sheet; FIG. 12(b) is a cross-sectional view of the main sheet portion, and FIG. 12(b) is a cross-sectional view of the unnecessary sheet portion; FIG. 13(a) is a cross-sectional view of the main sheet portion, and FIG. 13 ... 16(a) is a cross-sectional view showing a sheet main body portion in a state where a peeling defect (insufficient peeling) has occurred in the sheet main body portion shown in FIG. 14 in a lamination process (second process) using a conventional multilayer sheet. 16(b) is a cross-sectional view showing a sheet main body portion in a state where a peeling defect (insufficient peeling) has occurred in the first process, and 16(b) is a cross-sectional view showing a sheet main body portion in a state where a peeling defect (insufficient peeling) has occurred in the second process. 16(a) is a cross-sectional view showing a sheet main body portion in a state where a peeling defect (insufficient peeling) has occurred in the lamination process (first process and second process) using a conventional multilayer sheet. 17(a) is a cross-sectional view showing a sheet main body portion in a state where a peeling defect (insufficient peeling) has occurred in the first process, and 17(b) is a cross-sectional view showing a sheet main body portion in a state where a peeling defect (insufficient peeling) has occurred in the second process.

[0025] (Peeling defects in conventional multilayer sheets) When examining the multilayer sheet of the present embodiment described below, the inventors first examined peeling defects that occur when a lamination process including a half-cut process and a second area peeling process is performed using a conventional multilayer sheet having a three-layer structure.

[0026] FIG. 1 is a schematic diagram illustrating an example of a lamination process using a multilayer sheet. Specifically, it is a side view of a strip-shaped multilayer sheet undergoing lamination, viewed from one side in the width direction of the strip-shaped multilayer sheet. Note that detailed cross-sectional structures of the multilayer sheet are omitted in FIG. 1 (details of the cross-sectional structures will be described in other drawings). In FIG. 1 and other drawings described below, the X, Y, and Z directions refer to mutually perpendicular directions, the XY plane including the X and Y directions refers to a horizontal plane, and the Z direction refers to a vertical direction. In these drawings, the X1 direction may be referred to as the right (side, direction), the X2 direction as the left (side, direction), the Z1 direction as the top (side, direction), the Z2 direction as the bottom (side, direction), and the Y direction as the width direction (of the multilayer sheet).

[0027] The transport path of the multilayer sheet 10 during lamination is outlined below. First, the multilayer sheet 10 is supplied from a multilayer sheet supply roll (not shown) and transported from the right side of the figure to the half-cut section HC. After passing through the half-cut section HC, the multilayer sheet 10 is transported further leftward to reach the peeling section P. At the peeling section P, a portion of the multilayer sheet 10 is peeled off from the multilayer sheet 10, separating the multilayer sheet 10 into a main sheet portion 10A and an unnecessary sheet portion 10B. The main sheet portion 10A is then transported further leftward from the peeling section P and moves to the laminating section R. Meanwhile, the unnecessary sheet portion 10B is transported downward and to the right from the peeling section P, and then transported further rightward, and finally wound up on an unnecessary portion recovery roll (not shown).

[0028] The half-cut section HC has a pair of rolls arranged with their rotation axes parallel to the Y direction (the direction perpendicular to the paper surface in FIG. 1 ), and this pair of rolls consists of a support roll 20 and a half-cut roll 22 arranged below the support roll 20 and facing the support roll 20, with at least one of the rolls being rotated by an electric motor. A flat blade for half-cutting, having a blade pattern corresponding to the shape to be used to half-cut the multilayer sheet 10, is attached to the outer circumferential surface of the half-cut roll 22. When the multilayer sheet 10 passes between the support roll 20 and the half-cut roll 22, the flat blade is pressed into one side of the multilayer sheet 10, thereby half-cutting the multilayer sheet 10.

[0029] The peeling section P includes a peeling claw 30 and a support roll 32 arranged with its rotation axis parallel to the Y direction. The peeling claw 30 is arranged so as to contact the underside of the multilayer sheet 10 located between the half-cut section HC and the laminating section R, and the support roll 32 is arranged so as to contact the underside of the sheet main body 10A located between the half-cut section HC and the laminating section R. In addition, in the conveying direction (X2 direction) of the multilayer sheet 10, the support roll 32 is arranged on the laminating section R side with respect to the peeling claw 30. The peeling claw 30 has a first support surface 30S1 that is parallel to the conveying direction (X2 direction) of the multilayer sheet 10 and contacts the underside of the multilayer sheet 10, and a second support surface 30S2 that contacts one side of the sheet-unnecessary section 10B and intersects the first support surface 30S1 at an acute angle. The vicinity of tip 30T where first support surface 30S1 and second support surface 30S2 intersect is curved. At tip 30T of peeling claw 30, multilayer sheet 10 that has passed through half-cut section HC and been transported to peeling section P is simultaneously subjected to tension pulling it to the left and tension pulling it to the lower right, separating multilayer sheet 10 into main sheet portion 10A that is transported to the left and unnecessary sheet portion 10B that is transported to the lower right.

[0030] During this separation, the underside of the sheet body 10A is supported by a support roll 32 that rotates in accordance with the transport of the sheet body 10A so that the sheet body 10A is not pulled downward immediately after separation. The separated sheet body 10A is then transported to the laminating unit R. The separated unnecessary sheet portion 10B is positioned on the lower right side of the peeling unit P, and when it is transported to a support roll 40 whose rotation axis is parallel to the Y axis, it changes its transport direction from the lower right to the right, using the support roll 40 as a fulcrum, and is finally taken up by an unnecessary portion recovery roll (not shown).

[0031] The laminating unit R includes a pair of pressure rolls 50, 52 arranged opposite each other with their rotation axes parallel to the Y direction, and at least one of the rolls is rotated by an electric motor. The laminating unit R also includes a heating means (e.g., a heater) (not shown). The heating means may be built into at least one of the pair of pressure rolls 50, 52, or may be arranged near the pressure rolls 50, 52. The pair of pressure rolls 50, 52 are arranged such that the pressure roll 50 is located above the pressure roll 52. During lamination, the outer peripheral surface of the pressure roll 50 presses the upper surface of the sheet main body 10A, and the outer peripheral surface of the pressure roll 52 presses the lower surface of the laminate target member 200. In the laminating unit R, the material to be laminated 200 is supplied from the underside of the sheet body 10A being conveyed to the laminating unit R near its entrance (near the right side of the laminating unit R), forming a laminate in which the sheet body 10A and the material to be laminated 200 are stacked together. When this laminate passes between the pressure roll 50 and the pressure roll 52, the laminate is heated and pressurized to obtain a laminated body. This completes the lamination process. The laminated body is then subjected to predetermined post-processing steps in sequence depending on the shape and structure of the final product.

[0032] On the other hand, a strip-shaped multilayer sheet 10 having a conventional three-layer structure used in lamination has a cross-sectional structure shown in Figure 9. The cross-sectional structure of the multilayer sheet 10 shown in Figure 9 illustrates the state immediately before half-cutting at the half-cut section HC. The multilayer sheet 10 has a three-layer structure in which a first base film 12, an adhesive film 14, and a second base film 16 are laminated in this order. Near the entrance of the half-cut section HC (near the right side of the half-cut section HC in Figure 1), the multilayer sheet 10 is positioned so that the first base film 12 faces downward, as shown in Figure 9. The surface of the multilayer sheet 10 on which the first base film 12 is provided is the surface to be half-cut (half-cut surface 10C), and the surface of the multilayer sheet 10 opposite the half-cut surface 10C is the surface not to be half-cut (non-half-cut surface 10N).

[0033] Furthermore, when the peel strength between the first base film 12 and the adhesive film 14 is p1, and the peel strength between the adhesive film 14 and the second base film 16 is p2, the peel strengths p1 and p2 can be set to satisfy any of the following formulas (A) to (C). However, for convenience of explanation, in the explanation of the first process and the second process described below, it is assumed that formula (A) is satisfied. For reference, in FIG. 9 and other drawings, the interfaces between the films and the peel strengths p1 and p2 are shown in correspondence as necessary. Formula (A) p1<p2 Formula (B) p1>p2 Formula (C) p1=p2

[0034] In the lamination process using the multilayer sheet 10, each step can be performed in two patterns (first process or second process). Note that although the order of steps is different between the first process and the second process, the final laminate obtained has the same structure. The first process and the second process are described in detail below.

[0035] <First Process> In the first process, a half-cutting step is first performed in the half-cut section HC, in which the multilayer sheet 10 is half-cut. In the half-cutting step, the multilayer sheet 10 is partially cut partway through the thickness direction from the surface (half-cut surface 10C) on which the first base film 12 of the multilayer sheet 10 is provided, so as to separate the adhesive film 14 along with the first base film 12. In this process, the half-cut surface 10C is divided into a first region and a region other than the first region (a second region) along the cutting line formed by the cutting. FIG. 10 shows an example of the multilayer sheet 10 after half-cutting. FIG. 10(a) is a plan view showing an example of the multilayer sheet 10 after half-cutting, as viewed from the half-cut surface 10C side, and FIG. 10(b) is a cross-sectional view taken along the line B-B in FIG. 10(a).

[0036] In the example shown in Figure 10, the half-cut surface 10C of the multilayer sheet 10 is divided by cutting lines CL into a plurality of circular first regions 10R1 formed at equal intervals along the longitudinal direction (or conveying direction) of the multilayer sheet 10, and a region other than the first regions 10R1 (second regions 10R2). The cutting lines CL are formed to extend from the half-cut surface 10C to the interface between the adhesive film 14 and the second base film 16. The shapes and sizes of the first regions 10R1 and the second regions 10R2 in the XY plane are appropriately selected depending on the shape and structure of the final product manufactured through lamination and subsequent post-processing, as well as the content of the post-processing after lamination. For example, if the final product is a semiconductor device, the shape and size of the first region 10R1 can be approximately the same as that of a semiconductor wafer, carrier wafer, or the like.

[0037] Next, as shown in FIG. 11 , a release tape 60 is applied to the half-cut surface 10C of the multilayer sheet 10 after half-cutting. The application position of this release tape 60 is not particularly limited as long as it can be applied to both the first region 10R1 and the second region 10R2. For example, as illustrated in FIG. 11 , it can be applied to the center of the width of the half-cut surface 10C so that the longitudinal direction of the release tape 60 is parallel to the longitudinal direction of the multilayer sheet 10. In the lamination process shown in FIG. 1 , a release tape application means for continuously applying the release tape 60 to the half-cut surface 10C can be provided between the half-cut section HC and the peeling section P. The configuration of the release tape application means is not particularly limited, but examples include a pressure roll that presses the adhesive surface of the release tape 60 supplied from a release tape 60 supply roll against the half-cut surface 10C to apply it. In this case, the pressure roll used to apply the release tape 60 is positioned on the underside of the multilayer sheet 10 between the half-cut section HC and the peeling section P. The adhesive strength between the release tape 60 and the half-cut surface 10C is set to be significantly greater than the adhesive strength between the films constituting the multilayer sheet 10.

[0038] When the multilayer sheet 10 with the release tape 60 attached thereto is transported to the peeling section P, the multilayer sheet 10 is separated into a sheet main body portion 10A1 (10A) and a sheet unnecessary portion 10B1 (10B) as illustrated in Fig. 12. At this time, (i) the second region peeling step and (ii) the first step (first base film peeling step) are carried out simultaneously. That is, in (i) the second region 10R2, peeling occurs at the interface between the second base film 16 and the adhesive film 14, and the second base film 16 after peeling becomes a member on the sheet main body portion 10A1 side, and the adhesive film 14 and the first base film 12 after peeling, together with the release tape 60 attached to the surface (half-cut surface 10C) of the first base film 12, become members on the sheet unnecessary portion 10B1 side. (ii) Furthermore, in the first region 10R1, peeling occurs at the interface between the adhesive film 14 and the first base film 12, and after peeling, the second base film 16 and the adhesive film 14 become components on the sheet main body portion 10A1 side, and the first base film 12 after peeling, together with the peel tape 60 attached to the surface (half-cut surface 10C) of the first base film 12, become components on the sheet-unnecessary portion 10B1 side.

[0039] 12A and 12B are cross-sectional views showing the cross-sectional structure of the multilayer sheet 10 after it has been separated into a main sheet portion 10A1 and an unnecessary sheet portion 10B1 in the first process by passing through a peeling section P. Here, Fig. 12A is a cross-sectional view showing the cross-sectional structure of the main sheet portion 10A1 (10A) cut at the center in its width direction at position L1 in Fig. 1, and Fig. 12B is a cross-sectional view showing the cross-sectional structure of the unnecessary sheet portion 10B1 (10B) cut at the center in its width direction at position L2 in Fig. 1. As shown in Figure 12, the sheet main body portion 10A1 has a layer structure in which a second base film 16 and an adhesive film 14 consisting only of a portion corresponding to the first region 10R1 are laminated in this order, and the sheet-unnecessary portion 10B1 has a layer structure in which a first base film 12 and an adhesive film 14 consisting only of a portion corresponding to the second region 10R2 are laminated in this order, and a peel-off tape 60 is attached to the surface of the first base film 12 opposite to the side on which the adhesive film 14 is provided (half-cut surface 10C).

[0040] Here, the peel strengths p1 and p2 satisfy the formula (A) "p1 < p2" as described above. Therefore, in the first step (first base film peeling step), peeling occurs in the first region 10R1 at the interface (between the first base film 12 and the adhesive film 14) with the smallest peel strength among the interfaces formed between the films constituting the multilayer sheet 10. On the other hand, in the second region 10R2, initial settings are made before the start of the continuous lamination process shown in FIG. 1 so that peeling automatically occurs at the interface between the adhesive film 14 and the second base film 16 in the second region peeling step, regardless of whether formula (A) is satisfied.

[0041] This initial setting is performed as follows. First, before the start of the continuous lamination process shown in FIG. 1 , the interface between the adhesive film 14 and the second base film 16 is manually and forcibly peeled in advance at the peeling section P to separate the first sheet consisting of only the second base film 16 and the second sheet consisting of a laminate of the first base film 12 and the adhesive film 14. The manually separated first sheet (second base film 16) is then pulled and set to a position where a subsequent process will be performed, such as the lamination section R, and the manually separated second sheet (laminate of the first base film 12 and the adhesive film 14) is pulled and set via the support roll 40 to a waste portion recovery roll (not shown). If the continuous lamination process is performed after performing this initial setting, peeling will occur automatically and continuously at the interface between the adhesive film 14 and the second base film 16 in the peeling section P during the lamination process, as specified by the initial setting.

[0042] In order for peeling to occur automatically and continuously at the interface between the adhesive film 14 and the second base film 16 only in the second region 10R2 in the peeling section P after the continuous lamination process has begun following the initial settings, the first region 10R1 and the second region 10R2 must each satisfy the following conditions: (i) The first region 10R1 must be a discontinuous region (or a plurality of discretely dispersed regions) in the longitudinal direction (conveying direction) of the multilayer sheet 10, as exemplified in Figure 10(a). (ii) The second region 10R2 must be a continuous region in the longitudinal direction (conveying direction) of the multilayer sheet 10, as exemplified in Figure 10(a).

[0043] The unnecessary sheet portion 10B1 separated in the peeling section P is transported to the right in FIG. 1 , using the support roll 40 as a fulcrum, and is finally wound up on an unnecessary portion recovery roll (not shown). The main sheet portion 10A1 separated in the peeling section P is transported to the laminating section R in FIG. 1 . Near the entrance of the laminating section R, a laminate is formed by laminating a target material 200 onto the surface of the adhesive film 14 corresponding to the first region 10R1 of the main sheet portion 10A1. This laminate is then heated and pressurized as it passes between a pair of pressure rolls 50, 52 constituting the laminating section R, thereby obtaining a laminate. This completes the second process (laminate formation process). The resulting laminate is then subjected to a predetermined post-process depending on the structure, shape, etc. of the final product.

[0044] <Second Process> In the second process, first, a half-cutting step is performed in which the multilayer sheet 10 is half-cut in the half-cut section HC. The half-cutting step performed in the second process is performed in the same manner as the half-cutting step performed in the first process. This results in a half-cut multilayer sheet 10 as shown in Figure 10.

[0045] The half-cut multilayer sheet 10 is conveyed as is to the peeling section P, where the multilayer sheet 10 is separated into a sheet main body section 10A2 (10A) and an unnecessary sheet section 10B2 (10B) as shown in Fig. 13. At this time, a second region peeling step is carried out. That is, in the second region 10R2, peeling occurs at the interface between the second base film 16 and the adhesive film 14, and after peeling, the second base film 16 becomes a component on the sheet main body section 10A2 side, and the adhesive film 14 and first base film 12 become components on the unnecessary sheet section 10B2 side.

[0046] 13A and 13B are cross-sectional views showing the cross-sectional structure of the multilayer sheet 10 after it has passed through the peeling section P in the second process and been separated into a main sheet portion 10A2 and an unnecessary sheet portion 10B2. Fig. 13A is a cross-sectional view showing the cross-sectional structure of the main sheet portion 10A2 (10A) cut at the center in the width direction at position L1 in Fig. 1, and Fig. 13B is a cross-sectional view showing the cross-sectional structure of the unnecessary sheet portion 10B2 (10B) cut at the center in the width direction at position L2 in Fig. 1. As shown in Figure 13, the sheet main body portion 10A2 has a layer structure in which a second base film 16, an adhesive film 14 consisting only of a portion corresponding to the first region 10R1, and a first base film 12 consisting only of a portion corresponding to the first region 10R1 are laminated in this order, and the sheet-unnecessary portion 10B2 has a layer structure in which a first base film 12 consisting only of a portion corresponding to the second region 10R2 and an adhesive film 14 consisting only of a portion corresponding to the second region 10R2 are laminated in this order.

[0047] Here, the peel strengths p1 and p2 satisfy the formula (A) "p1 < p2" as described above. However, in the second region 10R2, an initial setting is made before the start of the continuous lamination process shown in Figure 1 so that peeling automatically occurs at the interface between the adhesive film 14 and the second base film 16 in the second region peeling step, regardless of whether formula (A) is satisfied or not. This initial setting is the same as the initial setting in the first process.

[0048] The unnecessary sheet portion 10B2 separated in the peeling section P is transported in the right direction in FIG. 1 with the support roll 40 as a fulcrum, and is finally taken up by an unnecessary portion recovery roll (not shown).

[0049] Meanwhile, as the sheet main body 10A2 separated at the peeling section P is transported to the laminating section R in FIG. 1 , a peeling tape 60 is attached to the half-cut surface 10C (first region 10R1). The attachment position of this peeling tape 60 is not particularly limited as long as it can be attached to the half-cut surface 10C (first region 10R1). For example, as illustrated in FIG. 14 , the peeling tape 60 can be attached to the widthwise center of the half-cut surface 10C (first region 10R1) so that the longitudinal direction of the peeling tape 60 is parallel to the longitudinal direction (transport direction) of the sheet main body 10A2. In the laminating process shown in FIG. 1 , a peeling tape attachment means for continuously attaching the peeling tape 60 to the half-cut surface 10C (first region 10R1) can be provided between position L1 and the laminating section R. The configuration of the release tape applying means is not particularly limited, but may be, for example, a pressure roll that presses the adhesive surface of the release tape 60 supplied from a release tape 60 supply roll against the half-cut surface 10C (first region 10R1) to apply the tape. In this case, the pressure roll used to apply the release tape 60 is disposed on the underside of the sheet main body 10A2, which is located between position L1 and the laminating section R. The adhesive strength between the release tape 60 and the half-cut surface 10C (first region 10R1) is set to be significantly greater than the adhesive strength between the films that make up the sheet main body 10A2.

[0050] 1 , the sheet main body 10A2 to which the release tape 60 has been attached is further transported to the laminating unit R. As the release tape 60 is pulled in a direction (e.g., a lower right direction in FIG. 1 ) intersecting the transport direction (X2 direction) of the sheet main body 10A2, the release tape 60 is peeled from the sheet main body 10A2 while remaining integrated with the first base film 12. This completes the first step (first base film peeling step). The means for performing the first step (first base film peeling step) is not particularly limited, and may be, for example, a means having a configuration substantially similar to that of the peeling unit P illustrated in FIG. 1 . The first base film 12, which has been peeled from the sheet main body 10A2 while remaining integrated with the release tape 60, is ultimately wound up on a base film recovery roll (not shown).

[0051] In the first step (first base film peeling step), peeling occurs at the interface between the first base film 12 and the adhesive film 14, which has a relatively weak peel strength among the interfaces between the films constituting the sheet main body 10A2. Therefore, the sheet main body 10A2 to which the peel tape 60 is attached is separated into two members with this interface as the peel interface.

[0052] For reference, Fig. 15 shows the cross-sectional structure of the sheet body 10A2' (10A) obtained by performing the first step (first substrate film peeling step) on the sheet body 10A2. As shown in Fig. 15, the sheet body 10A2' has the same cross-sectional structure as the sheet body 10A1 shown in Fig. 12(a).

[0053] The sheet body 10A2′ from which the first base film 12 has been peeled off after the first step (first base film peeling step) is transported to the laminating unit R in FIG. 1 . Near the entrance of the laminating unit R, a laminate is formed by laminating a member to be laminated 200 onto the surface of the adhesive film 14 corresponding to the first region 10R1 of the sheet body 10A2′. This laminate is heated and pressurized as it passes between a pair of pressure rolls 50, 52 that constitute the laminating unit R, thereby obtaining a laminate. This completes the second step (laminate formation step). The resulting laminate is then subjected to a predetermined post-processing step depending on the structure, shape, etc. of the final product.

[0054] <Modes of Occurrence of Peel Defects in the First Process and the Second Process and Their Causes> The above description of the first process and the second process is based on the assumption that the processes proceed under ideal conditions without any peel defect. However, when the inventors actually tried the first process and the second process, they confirmed that peel defects (insufficient peeling) occurred as described in (a) and (b) below.

[0055] (a) In the first process, when the second region peeling step was performed in the peeling portion P, in the second region 10R2, the adhesive film 14 did not peel cleanly at the interface between the adhesive film 14 and the second base film 16, and a part or all of the adhesive film 14 remained attached to the second base film 16 constituting the sheet main body portion 10A1, resulting in a peeling defect (insufficient peeling). (b) In the second process, when the second region peeling step was performed in the peeling portion P, the adhesive film 14 did not peel cleanly at the interface between the adhesive film 14 and the second base film 16, and a peeling defect (insufficient peeling) occurred in the second region 10R2, and a part or all of the adhesive film 14 remained attached to the second base film 16 constituting the sheet main body portion 10A2.

[0056] For reference, Fig. 16 shows an example of the cross-sectional structure of a cut surface cut at the widthwise center of a sheet main body 10A in which a peeling failure (insufficient peeling) occurred. Fig. 16(a) is a cross-sectional view showing an example of a sheet main body 10A1 in which a peeling failure (insufficient peeling) occurred in the first process, and Fig. 16(b) is a cross-sectional view showing an example of a sheet main body 10A2 in which a peeling failure (insufficient peeling) occurred in the second process. In the sheet main bodies 10A1 and 10A2 shown in Fig. 16, as is clear from a comparison with Figs. 12(a) and 13(a), the adhesive film 14, which should not be present in the second region 10R2, remains attached to the second base film 16.

[0057] The main reason for the peeling failure (insufficient peeling) as illustrated in Figure 16 is thought to be the following: "Even if the initial setting is such that peeling occurs at the interface between the second base film 16 and the adhesive film 14 in the second region 10R2, the peel strength p2 is relatively greater than the peel strength p1, so that the adhesive film 14 is more likely to adhere to the second base film 16 in the second region peeling step after the start of the lamination process."

[0058] On the other hand, if the main cause of the above-mentioned peel failure (insufficient peeling) is due to peel strengths p1 and p2 satisfying formula (A) "p1<p2," then it is thought that in order to suppress the occurrence of peel failure (insufficient peeling), peel strengths p1 and p2 should satisfy formula (B) "p1>p2" or formula (C) "p1=p2." Therefore, in the first process and the second process, the inventors performed lamination using a multilayer sheet 10 satisfying formula (B) or formula (C) instead of a multilayer sheet 10 satisfying formula (A).

[0059] As a result, when a multilayer sheet 10 satisfying formula (B) was used, the occurrence of the above-mentioned peeling failure (excessive peeling) was significantly suppressed. This is thought to be because, when formula (B) is satisfied, the adhesive film 14 adheres more firmly to the first base film 12 side than to the second base film 16 side, so that in the second region peeling step, peeling at the interface between the second base film 16 and the adhesive film 14 (the interface with the weakest peel strength) in the second region 10R2 continues to occur stably, as in the initial setting. However, when a multilayer sheet 10 satisfying formula (B) was used, the occurrence of new peeling failures (excessive peeling) shown in the following (c) and (d) was confirmed in the first step (first base film peeling step) performed on the first region 10R1.

[0060] (c) In the first process, a peeling failure (excessive peeling) occurred in the first region 10R1 of the multilayer sheet 10, in which not only the first base film 12 (the object to be peeled) but also the adhesive film 14 was peeled together with the first base film 12. (d) In the second process, a peeling failure (excessive peeling) occurred in the first region 10R1 of the sheet main body 10A2, in which not only the first base film 12 (the object to be peeled) but also the adhesive film 14 was peeled together with the first base film 12.

[0061] For reference, Fig. 17 shows an example of the cross-sectional structure of a cut surface cut at the widthwise center of a sheet main body portion 10A in which peeling failure (excessive peeling) occurred. Here, Fig. 17(a) is a cross-sectional view showing an example of a sheet main body portion 10A1 in which peeling failure (excessive peeling) occurred in the first process, and Fig. 17(b) is a cross-sectional view showing an example of a sheet main body portion 10A2' in which peeling failure (excessive peeling) occurred in the second process. In the sheet main bodies 10A1 and 10A2' shown in Fig. 17, as is clear from a comparison with Fig. 12(a) and Fig. 15, there are portions in the first region 10R1 where the adhesive film 14 that should originally be present is missing.

[0062] 17 may occur due to the following reason: "Because peel strength p1 is relatively greater than peel strength p2, adhesive film 14 adheres more firmly to first base film 12 than to second base film 16. As a result, in the first step (first base film peeling step) performed on first region 10R1, not only first base film 12 (the object to be peeled) but also adhesive film 14, integrated with first base film 12, is easily peeled."

[0063] Furthermore, it was confirmed that when a multilayer sheet 10 satisfying formula (C) was used, the peeling failure (too little peeling) illustrated in Fig. 16 and the peeling failure (too much peeling) illustrated in Fig. 17 occurred together. This is thought to be because formula (C) exhibits intermediate characteristics between formulas (A) and (B).

[0064] As explained above, when lamination was performed using a multilayer sheet 10 having a conventional three-layer structure, either one or both of the following peeling defects (1) and (2) occurred in both the first and second processes: (1) Peeling defects occurring in the second region peeling step (insufficient peeling as exemplified in FIG. 16 ) (2) Peeling defects occurring in the first step (first substrate film peeling step) (excessive peeling as exemplified in FIG. 17 ).

[0065] Based on the above findings, the present inventors have discovered the multilayer sheet of the present embodiment described below.

[0066] (Multilayer Sheet of the Present Embodiment) The multilayer sheet of the present embodiment includes a first base film, an adhesive film, a second base film, and a third base film, in which the first base film, the adhesive film, the second base film, and the third base film are laminated in this order, and satisfies the following formula (1): P1<P2<P3.

[0067] In formula (1), P1 represents the peel strength (N / 250 mm) between the first base film and the adhesive film, P2 represents the peel strength (N / 250 mm) between the adhesive film and the second base film, and P3 represents the peel strength (N / 250 mm) between the second base film and the third base film.

[0068] The multilayer sheet of this embodiment has a four-layer structure in which a third base film is newly provided on the second base film 16 side of the conventional three-layer multilayer sheet 10, and also satisfies formula (1). This makes it possible to significantly suppress the two types of peeling defects described above (the insufficient peeling exemplified in FIG. 16 and the excessive peeling exemplified in FIG. 17).

[0069] From formula (1), the ratios of the peel strengths at two interfaces adjacent in the thickness direction in the multilayer sheet of this embodiment are 1.0<P2 / P1 and 1.0<P3 / P2. However, if P2 / P1 or P3 / P2 is too close to 1.0, it may be difficult to intentionally and reproducibly cause peeling at any of the three interfaces. Therefore, P2 / P1 is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.3 or more. Furthermore, P3 / P2 is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.3 or more.

[0070] Next, details of a lamination process including a half-cutting step and a second region peeling step using the multilayer sheet of this embodiment are described below with reference to the drawings. In the following description of the components and parts constituting the multilayer sheet of this embodiment and the main sheet portion and unnecessary sheet portion obtained by separating the multilayer sheet into two, components and parts that are identical or similar in function, material, or location to those in the conventional three-layer multilayer sheet 10 are denoted by the same or similar reference numerals as those in the multilayer sheet 10. For reference, in FIG. 2 and other drawings, the multilayer sheet, main sheet portion, and unnecessary sheet portion of this embodiment are shown, as necessary, with the elastic moduli Q1, R, Q2, and Q3 of each film corresponding to each other, and the peel strengths P1, P2, and P3 of each film corresponding to each other.

[0071] Fig. 2 is a cross-sectional view showing an example of the cross-sectional structure of the multilayer sheet of this embodiment. The multilayer sheet 100 of this embodiment has a four-layer structure in which a first base film 12, an adhesive film 14, a second base film 16, and a third base film 18 are laminated in this order. The multilayer sheet 100 is positioned so that the first base film 12 is on the lower surface near the entrance of the half-cut portion HC (near the right side of the half-cut portion HC in Fig. 1), as shown in Fig. 2.

[0072] When laminating the multilayer sheet 100 of this embodiment, the lamination process shown in FIG. 1 can be applied, just as with a conventional multilayer sheet 10. The conveyance path of the multilayer sheet 100 of this embodiment during lamination is outlined below. First, the multilayer sheet 100 supplied from a multilayer sheet supply roll (not shown) is conveyed from the right side of the figure to the half-cutting section HC, where it is half-cut. Next, the half-cut multilayer sheet 100 is conveyed further leftward to reach the peeling section P. Then, at the peeling section P, some layers of the multilayer sheet 100 are peeled from the multilayer sheet 100, separating it into a main sheet portion 100A and an unnecessary sheet portion 100B. The main sheet portion 100A is then conveyed further leftward from the peeling section P to the laminating section R. The sheet body 100A moving to the laminating section R forms a laminate in which the sheet body 100A and the lamination target material 200 are stacked together, and this laminate is heated and pressed in the laminating section R to obtain a laminate. This completes the lamination process. The laminate is then subjected to various post-processing steps depending on the shape and structure of the final product. Meanwhile, the unnecessary sheet portion 100B is transported from the peeling section P downward and to the right, and then further transported to the right, and finally wound up on an unnecessary portion recovery roll (not shown).

[0073] When laminating using the multilayer sheet 100 of this embodiment, each step can be performed in two patterns (first process or second process) as in the case of laminating using the conventional multilayer sheet 10. The first process and second process will be described in detail below.

[0074] <First Process> In the first process, a half-cutting step is first performed in the half-cut section HC, in which the multilayer sheet 100 is half-cut. In the half-cutting step, the multilayer sheet 100 is partially cut partway through the thickness direction from the surface (half-cut surface 10C) on which the first base film is provided, so as to separate the first base film 12, the adhesive film 14, and the second base film 16. In this process, the half-cut surface 10C is divided into a first region and a region other than the first region (a second region) along a cutting line formed by the cutting. FIG. 3 shows an example of the multilayer sheet 100 after half-cutting. FIG. 3(a) is a plan view showing an example of the half-cut multilayer sheet 100 as viewed from the half-cut surface 10C, and FIG. 3(b) is a cross-sectional view taken along the line A-A in FIG. 3(a).

[0075] 3 is formed in the same manner as the example shown in Fig. 10, except that the cutting line CL provided on the multilayer sheet 100 is formed so as to extend from the half-cut surface 10C to the interface between the second base film 16 and the third base film 18. Next, in the same manner as when a release tape 60 is applied to a conventional multilayer sheet 10 after half-cutting (Fig. 11), a release tape 60 is applied to the half-cut surface 10C of the multilayer sheet 100 of this embodiment after half-cutting, as shown in Fig. 4.

[0076] When the multilayer sheet 100 with the release tape 60 attached thereto is transported to the peeling section P, the multilayer sheet 100 is separated into a sheet main body portion 100A1 (100A) and a sheet unnecessary portion 100B1 (100B) as illustrated in FIG. 5 . At this time, (i) the second region peeling step and (ii) the first step (first base film peeling step) are performed simultaneously. That is, in (i) the second region 10R2, peeling occurs at the interface between the third base film 18 and the second base film 16, and the third base film 18 after peeling becomes a member on the sheet main body portion 100A1 side, and the second base film 16, adhesive film 14, and first base film 12 after peeling, together with the release tape 60 attached to the surface (half-cut surface 10C) of the first base film 12, become members on the sheet unnecessary portion 10B1 side. (ii) Furthermore, in the first region 10R1, peeling occurs at the interface between the adhesive film 14 and the first base film 12, and after peeling, the third base film 18, the second base film 16 and the adhesive film 14 become components on the sheet main body portion 100A1 side, and the first base film 12 after peeling, together with the peel tape 60 attached to the surface (half-cut surface 10C) of the first base film 12, become components on the sheet-unnecessary portion 100B1 side.

[0077] 5A and 5B are cross-sectional views showing the cross-sectional structure of the multilayer sheet 100 after it has passed through the peeling section P in the first process and been separated into a main sheet portion 100A1 and an unnecessary sheet portion 100B1. Here, Fig. 5A is a cross-sectional view showing the cross-sectional structure of the main sheet portion 100A1 (100A) cut at the center in the width direction at position L1 in Fig. 1, and Fig. 5B is a cross-sectional view showing the cross-sectional structure of the unnecessary sheet portion 100B1 (100B) cut at the center in the width direction at position L2 in Fig. 1. As shown in Figure 5, the sheet main body portion 100A1 has a layer structure in which a third base film 18, a second base film 16 consisting only of a portion corresponding to the first region 10R1, and an adhesive film 14 consisting only of a portion corresponding to the first region 10R1 are laminated in this order, and the sheet-unnecessary portion 100B1 has a layer structure in which a first base film 12, an adhesive film 14 consisting only of a portion corresponding to the second region 10R2, and a second base film 16 consisting only of a portion corresponding to the second region 10R2 are laminated in this order, and a peel-off tape 60 is attached to the surface of the first base film 12 opposite to the side on which the adhesive film 14 is provided (half-cut surface 10C).

[0078] Here, the peel strengths P1, P2, and P3 satisfy the formula (1) "P1 < P2 < P3" as described above. Therefore, in the first step (first base film peeling step), peeling occurs in the first region 10R1 at the interface with the smallest peel strength (the interface between the first base film 12 and the adhesive film 14) among the interfaces formed between the films constituting the multilayer sheet 100. On the other hand, in the second region 10R2, initial settings are made before the start of the continuous lamination process shown in FIG. 1 so that peeling automatically occurs at the interface between the second base film 16 and the third base film 18 in the second region peeling step.

[0079] This initial setting is performed as follows. First, before the start of the continuous lamination process shown in Fig. 1 , the interface between the second substrate film 16 and the third substrate film 18 is manually and forcibly peeled off in advance in the peeling section P to separate the second substrate film 16 into a first sheet consisting of only the third substrate film 18 and a second sheet consisting of a laminate of the first substrate film 12, the adhesive film 14, and the second substrate film 16 laminated in this order. The manually separated first sheet (third substrate film 18) is then pulled and set to a position where a subsequent process will be performed, such as the laminating section R, and the manually separated second sheet (a laminate of the first substrate film 12, the adhesive film 14, and the second substrate film 16 laminated in this order) is pulled and set via the support roll 40 to a waste portion recovery roll (not shown). After performing such initial settings, if a continuous lamination process is carried out, peeling will occur automatically and continuously at the interface between the second substrate film 16 and the third substrate film 18 in the peeling section P during the lamination process, as per the initial settings for the second region 10R2.

[0080] In order for peeling to occur automatically and continuously at the interface between the second base film 16 and the third base film 18 only in the second region 10R2 in the peeling section P after the continuous lamination process has begun following the initial settings, the first region 10R1 and the second region 10R2 must each satisfy the following conditions: (i) The first region 10R1 must be a discontinuous region (or a plurality of discretely dispersed regions) in the longitudinal direction (conveying direction) of the multilayer sheet 100, as exemplified in Figure 3(a). (ii) The second region 10R2 must be a continuous region in the longitudinal direction (conveying direction) of the multilayer sheet 100, as exemplified in Figure 3(a).

[0081] The unnecessary sheet portion 100B1 separated in the peeling section P is transported to the right in FIG. 1 using the support roll 40 as a fulcrum and is finally wound up on a waste portion recovery roll (not shown). The main sheet portion 100A1 separated in the peeling section P is transported to the laminating section R in FIG. 1. Near the entrance of the laminating section R, a laminate is formed by laminating a target material 200 onto the surface of the adhesive film 14 corresponding to the first region 10R1 of the main sheet portion 100A1. This laminate is then heated and pressurized as it passes between a pair of pressure rolls 50, 52 constituting the laminating section R, thereby obtaining a laminate. This completes the second process (laminate formation process). The resulting laminate is then subjected to a predetermined post-process depending on the structure, shape, etc. of the final product.

[0082] <Second Process> In the second process, first, a half-cutting step is performed in which the multilayer sheet 100 is half-cut in the half-cut section HC. The half-cutting step performed in the second process is performed in the same manner as the half-cutting step performed in the first process. This results in the half-cut multilayer sheet 100 shown in Figure 3.

[0083] The half-cut multilayer sheet 100 is conveyed as is to a peeling section P, where the multilayer sheet 100 is separated into a sheet main body section 100A2 (100A) and an unnecessary sheet section 100B2 (100B) as shown in Fig. 6 . At this time, a second region peeling step is carried out. That is, in the second region 10R2, peeling occurs at the interface between the third base film 18 and the second base film 16, and after peeling, the third base film 18 becomes a component on the sheet main body section 100A2 side, and the second base film 16, adhesive film 14, and first base film 12 become components on the unnecessary sheet section 100B2 side.

[0084] 6A and 6B are cross-sectional views showing the cross-sectional structure of the multilayer sheet 100 after it has passed through the peeling section P in the second process and been separated into a main sheet portion 100A2 and an unnecessary sheet portion 100B2. Here, Fig. 6A is a cross-sectional view showing the cross-sectional structure of the main sheet portion 100A2 (100A) cut at the center in its width direction at position L1 in Fig. 1, and Fig. 6B is a cross-sectional view showing the cross-sectional structure of the unnecessary sheet portion 100B2 (100B) cut at the center in its width direction at position L2 in Fig. 1. As shown in Figure 6, the sheet main body portion 100A2 has a layer structure in which a third base film 18, a second base film 16 consisting only of a portion corresponding to the first region 10R1, an adhesive film 14 consisting only of a portion corresponding to the first region 10R1, and a first base film 12 consisting only of a portion corresponding to the first region 10R1 are laminated in this order, and the sheet-unnecessary portion 100B2 has a layer structure in which a first base film 12 consisting only of a portion corresponding to the second region 10R2, an adhesive film 14 consisting only of a portion corresponding to the second region 10R2, and a second base film 16 consisting only of a portion corresponding to the second region 10R2 are laminated in this order.

[0085] Here, the peel strengths P1, P2, and P3 satisfy the formula (1) "P1 < P2 < P3" as described above. However, in the second region 10R2, an initial setting is made before the start of the continuous lamination process shown in Fig. 1 so that peeling automatically occurs at the interface between the second base film 16 and the third base film 18 in the second region peeling step, regardless of whether formula (1) is satisfied. This initial setting is the same as the initial setting in the first process.

[0086] The unnecessary sheet portion 100B2 separated in the peeling section P is transported in the right direction in FIG. 1 with the support roll 40 as a fulcrum, and is finally taken up by an unnecessary portion recovery roll (not shown).

[0087] Meanwhile, a release tape 60 is attached to the half-cut surface 10C (first region 10R1) of the sheet main body 100A2 separated at the peeling section P while it is being transported to the laminating section R in Fig. 1. The attachment position of this release tape 60 is not particularly limited as long as it can be attached to the half-cut surface 10C (first region 10R1). However, in the same way as when the release tape 60 is attached to the sheet main body 10A2 obtained by separating a conventional multilayer sheet 10 at the peeling section P (Fig. 14), the release tape 60 is attached to the half-cut surface 10C (first region 10R1) of the sheet main body 100A2 as shown in Fig. 7.

[0088] 1 , the sheet main body 100A2 to which the release tape 60 has been attached is further transported to the laminating section R, whereby the release tape 60 is pulled in a direction (for example, the lower right direction in FIG. 1 ) intersecting the transport direction (X2 direction) of the sheet main body 100A2, whereby the release tape 60 is peeled off from the sheet main body 100A2 while remaining integrated with the first base film 12. This completes the first step (first base film peeling step). The first base film 12, which has been peeled off from the sheet main body 100A2 while remaining integrated with the release tape 60, is finally taken up on a base film recovery roll (not shown).

[0089] In the first step (first base film peeling step), peeling occurs at the interface between the first base film 12 and the adhesive film 14, which has the weakest peel strength among the interfaces between the films constituting the sheet main body 100A2. Therefore, the sheet main body 100A2 to which the peel tape 60 is attached is separated into two members with this interface as the peel interface.

[0090] For reference, Fig. 8 shows the cross-sectional structure of the sheet body 100A2' (100A) obtained by performing the first step (first base film peeling step) on the sheet body 100A2. As shown in Fig. 8, the sheet body 100A2' has the same cross-sectional structure as the sheet body 100A1 shown in Fig. 5(a).

[0091] The sheet body 100A2′ from which the first base film 12 has been peeled off after the first step (first base film peeling step) is transported to the laminating unit R in FIG. 1 . Near the entrance of the laminating unit R, a laminate is formed by laminating a member to be laminated 200 onto the surface of the adhesive film 14 corresponding to the first region 10R1 of the sheet body 100A2′. This laminate is heated and pressurized as it passes between a pair of pressure rolls 50, 52 that constitute the laminating unit R, thereby obtaining a laminate. This completes the second step (laminate formation step). The resulting laminate is then subjected to a predetermined post-process depending on the structure, shape, etc. of the final product.

[0092] <Method for manufacturing laminated body> Specific examples of the lamination process using the multilayer sheet 100 of this embodiment have been described above with reference to the drawings. However, as long as the lamination process using the multilayer sheet 100 of this embodiment (in other words, the method for manufacturing a laminated body) includes at least the half-cutting step, the second region peeling step, the first step, and the second step described below, the embodiment is not limited to only the specific examples described above (the first process and the second process).

[0093] Half-cutting process: A process of partially cutting the multilayer sheet 100 from the surface (half-cut surface 10C) on which the first base film 12 of the multilayer sheet 100 is provided, halfway through the thickness of the multilayer sheet 100, so as to separate the first base film 12, the adhesive film 14, and the second base film 16, and simultaneously dividing the surface (half-cut surface 10C) on which the first base film 12 of the multilayer sheet 100 is provided into a first region 10R1 and a second region 10R2, which is a region other than the first region 10R1, using the cutting line CL formed by the cutting as a boundary line.

[0094] Second Region Peeling Step: A step of peeling the second region 10R2 at the interface between the second base film 16 and the third base film 18.

[0095] First step: A step of peeling the first base film 12 and the adhesive film 14 at the interface therebetween in the first region 10R1.

[0096] Second step: A step of forming a laminate by bonding a laminate target material 200 to the surface of the adhesive film 14 of the sheet main body portions 100A1, 100A2' (a sheet in which the second base film 16 and the adhesive film 14 are laminated in this order on one side of the third base film 18 and in the first region 10R1), which is one of the two sheets obtained by separating the multilayer sheet 100 into two in its thickness direction by at least going through the second region peeling step and the first step, and then heating and pressurizing the laminate obtained.

[0097] Here, the order of performing the second area peeling step and the first step may be such that the second area peeling step and the first step are performed substantially simultaneously, as in the first process, or such that the second area peeling step is performed followed by the first step, as in the second process. The planar shape of the multilayer sheet 100 used in the method for producing a laminate according to this embodiment is not particularly limited and can be appropriately selected depending on the implementation of the lamination process. For example, if the lamination process is a continuous process as illustrated in Figure 1, the multilayer sheet may be a strip-shaped sheet elongated in the longitudinal direction, as illustrated in Figures 1 and 2. If the lamination process is a sheet-by-sheet process, the multilayer sheet may be a rectangular or rectangular sheet with an aspect ratio of approximately 1:3 to 3:1.

[0098] The planar shape of the first region 10R1 is selected as appropriate depending on the shape and structure of the laminate to be manufactured and the final product, and can be, for example, circular, approximately circular, or polygonal. When the multilayer sheet 100 used in the lamination process is a strip-shaped sheet, the planar shape of the first region 10R1 may be a single continuous region along the longitudinal direction of the strip-shaped multilayer sheet 100, but is typically preferably a plurality of regions (e.g., multiple circular or approximately circular regions) arranged along the longitudinal direction of the strip-shaped multilayer sheet 100. The lamination target member 200 constituting the laminate can be selected depending on the various post-processing steps to be performed after the laminate manufacturing method of this embodiment and the shape and structure of the final product manufactured through these post-processing steps. For example, a semiconductor wafer or a glass wafer (glass carrier substrate) can be used.

[0099] <Post-Processing for Laminate> As described above, the content of the post-processing performed on the laminate obtained by the first process or the second process is determined appropriately depending on the structure, shape, etc. of the final product. However, when the final product is a semiconductor device, for example, after the second process (laminate formation process) is completed, the laminate is separated at the interface between the adhesive film 14 and the second base film 16 to obtain a laminate (a laminate of the laminate target member 200 and the adhesive film 14). Various processes necessary for manufacturing a semiconductor device (e.g., an electrode formation process, a mounting process, a molding process, a polishing process, a wiring formation process, etc.) are performed on the laminate target member 200. In this case, a glass wafer (glass carrier substrate), a semiconductor wafer, etc. are used as the laminate target member 200 depending on the manufacturing process of the semiconductor device.

[0100] <Details of Multilayer Sheet> Next, details of each film constituting the multilayer sheet 100 of this embodiment and preferred characteristic values ​​will be described below.

[0101] In addition to satisfying formula (1), the multilayer sheet 100 of this embodiment more preferably satisfies the following formula (2): Q2 / Q3≦2.0 (2) In formula (2), Q2 represents the modulus of elasticity (MPa) of the second base film, and Q3 represents the modulus of elasticity (MPa) of the third base film. In the following description, the modulus of elasticity (MPa) of the first base film will be referred to as Q1, and the modulus of elasticity (MPa) of the adhesive film (in an uncured state) will be referred to as R.

[0102] The multilayer sheet 100 of the present embodiment, compared to the conventional three-layer multilayer sheet 10, has four film layers constituting the multilayer sheet 100, and satisfies formula (1). This significantly reduces the two types of peeling defects (excessive peeling and insufficient peeling) that occur in the conventional three-layer multilayer sheet 10. However, it has been confirmed that a new type of peeling defect may occur in the multilayer sheet 100 of the present embodiment due to the four-layer structure. This peeling defect occurs when wrinkles form between the third substrate film 18 and the second substrate film 16 constituting the sheet main body portion 100A in the second step (laminate formation step), and unintended peeling occurs at the interface between the third substrate film 18 and the second substrate film 16, starting from these wrinkles (hereinafter, this peeling defect may be referred to as "wrinkle-induced peeling"). The inventors therefore investigated the cause of wrinkle-induced peeling. As a result, it was found that when tension is applied to the third base film 18 in its longitudinal direction in the second step, if the third base film 18 is too soft relative to the second base film 16, the third base film 18 will stretch in the longitudinal direction, causing wrinkles to form between the third base film 18 and the second base film 16, which will lead to wrinkle-induced peeling.

[0103] Based on the above findings, the present inventors have found that wrinkle-induced peeling can be significantly suppressed if formula (2) is satisfied. From the viewpoint of further suppressing wrinkle-induced peeling, Q2 / Q3 is preferably 1.35 or less, and even more preferably 1.1 or less. While the lower limit of Q2 / Q3 is not particularly limited, from the viewpoint of the availability of films usable as the second base film 16 and the third base film 18, it is preferably 0.2 or more, and more preferably 0.4 or more, in practice.

[0104] The elastic modulus R of the adhesive film 14 is not particularly limited, but if the elastic modulus R is too large, the adhesive film 14 is more likely to self-destruct during the lamination process shown in Figure 1, which may result in poor peeling. Therefore, the elastic modulus R of the adhesive film 14 is preferably 20 MPa or less, and more preferably 10 MPa or less. The lower limit of the elastic modulus R is not particularly limited, but from a practical standpoint, it is preferably 1.0 MPa or more, and more preferably 0.5 MPa or more.

[0105] Furthermore, the values ​​of the peel strengths P1, P2, and P3 are not particularly limited as long as they satisfy formula (1), but the peel strength P1 is preferably 0.1 N / 250 mm or more and less than 5 N / 250 mm, more preferably 0.1 N / 250 mm to 1 N / 250 mm, and even more preferably 0.1 N / 250 mm to 0.5 N / 250 mm; the peel strength P2 is preferably more than 0.1 N / 250 mm and 5 N / 250 mm or less, more preferably more than 0.5 N / 250 mm and 5 N / 250 mm or less, and even more preferably more than 0.5 N / 250 mm and 1.5 N / 250 mm or less; and the peel strength P3 is preferably 0.5 N / 250 mm to 15 N / 250 mm, more preferably 1 N / 250 mm to 10 N / 250 mm, and even more preferably more than 1.5 N / 250 mm and 10 N / 250 mm or less. By setting the peel strength P3 to 15 N / 250 mm or less, the second region peeling step can be carried out stably.

[0106] The multilayer sheet 100 of this embodiment has a layered structure in which a first substrate film 12, an adhesive film 14, a second substrate film 16, and a third substrate film 18 are laminated in this order. Each of the films 12, 14, 16, and 18 has a uniform thickness in the horizontal direction (X and Y directions) and is not pre-cut (i.e., no cutting line CL is provided to divide each film horizontally). The planar shape of the multilayer sheet 100 of this embodiment is not particularly limited and can be appropriately selected to suit the lamination process. For example, when lamination is performed using a continuous processing method as illustrated in FIG. 1 , the multilayer sheet 100 of this embodiment is typically used as a strip-shaped sheet. When lamination is performed using a batch processing method, the multilayer sheet 100 of this embodiment is typically used as a rectangular sheet with an aspect ratio of approximately 1:3 to 3:1.

[0107] Furthermore, the first base film 12, adhesive film 14, second base film 16, and third base film 18 are not particularly limited in material, thickness, etc., as long as they satisfy formula (1) and the adhesive film 14 has adhesiveness and hardens when heated. However, it is particularly preferable that these films 12, 14, 16, and 18 be the films described below.

[0108] First Base Film 12 Examples of materials constituting the first base film 12 include polyolefin resins such as polypropylene (PP) resin and polymethylpentene resin, polyester resins such as polyethylene terephthalate (PET) resin and polyethylene naphthalate resin, polyimide resin, polyetherimide resin, and other resin materials. The first base film 12 may be a single-layer film composed of only one type of resin material, or a multilayer film composed of two types of films. However, when the first base film 12 is composed of a multilayer film, the adhesive strength between each film constituting the multilayer structure of the first base film 12 is set to be sufficiently greater than the peel strengths P1, P2, and P3 so that peeling does not occur at the interface between the films when an external force is applied to the multilayer sheet 100 in the thickness direction at the peeling portion P or the like. In addition, it is preferable that the surface of the first base film 12 (at least the surface that comes into close contact with the adhesive film 14, or both surfaces) be release-treated with a release agent or the like. The thickness of the first base film 12 is not particularly limited, but is preferably 15 μm to 100 μm, and more preferably 20 μm to 50 μm, from the viewpoints of cost, strength, workability, etc. Examples of the release agent include a silicone-based release agent, a long-chain alkyl-based release agent, and a fluorine-based release agent.

[0109] Adhesive Film 14 The adhesive film 14 is a film that has adhesive properties and hardens when heated, and is generally composed of a thermosetting resin composition. Examples of such thermosetting resin compositions include a resin composition containing an epoxy resin, a curing agent, and an inorganic filler. The thermosetting resin composition that constitutes the adhesive film 14 may also contain a black pigment such as carbon, if necessary. Using a black adhesive film 14 containing dispersed black pigment can ensure the concealment of components (e.g., semiconductor elements) formed or placed on one or the other side of the adhesive film 14 in a post-lamination process, and can also enable laser marking of the cured layer of the adhesive film 14.

[0110] The thickness of the adhesive film 14 is not particularly limited, but is preferably 1 μm to 50 μm, more preferably 10 μm to 50 μm, and even more preferably 15 μm to 40 μm, from the viewpoints of ensuring sufficient adhesion and suppressing warping of the obtained laminate. If hiding properties are required in a post-lamination process, the thickness of the black adhesive film 14 is preferably 10 μm or more from the viewpoint of ensuring hiding properties.

[0111] When the thermosetting resin composition constituting the adhesive film 14 contains an epoxy resin, a curing agent, and an inorganic filler, and further contains a black pigment as required, it is preferable to use the materials described below.

[0112] Examples of epoxy resins include bisphenol A epoxy resins, bisphenol F epoxy resins, phenol novolac epoxy resins, alicyclic epoxy resins, siloxane epoxy resins, biphenyl epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, hydantoin epoxy resins, and naphthalene ring-containing epoxy resins. Two or more types can be used in combination. Furthermore, from the viewpoints of adhesiveness and the reliability of the resulting laminate and the final product, it is preferable to use a combination of a solid epoxy resin and a liquid epoxy resin at room temperature. The content of the epoxy resin in the thermosetting resin composition is not particularly limited, but is preferably 15 to 45 parts by weight per 100 parts by weight of the nonvolatile components constituting the thermosetting resin composition to ensure sufficient adhesion to the laminate target member 200 in the second step (laminate formation step).

[0113] Examples of the curing agent include known curing agents for epoxy resins, such as imidazole-based curing agents, amine-based curing agents, and phosphorus-based curing agents. From the viewpoint of the storage stability and reactivity of the thermosetting resin composition constituting the adhesive film 14, it is preferable to use a combination of at least 2-phenyl-1-benzyl-1H-imidazole, dicyandiamide, and other curing agents. The content of the curing agent is not particularly limited, but is preferably 0.5 to 3 parts by mass per 100 parts by mass of the nonvolatile components constituting the thermosetting resin composition. In this specification, the term "curing agent" includes not only curing agents in the narrow sense, but also compounds known as curing catalysts and curing accelerators.

[0114] The inorganic material constituting the inorganic filler is SiO ２ (Silica), Al ２ O ３ Examples of inorganic fillers include alumina, AlN, and BN, with silica being preferred from the viewpoint of reducing the linear expansion coefficient, and alumina and BN being preferred from the viewpoint of improving thermal conductivity. The content of the inorganic filler is not particularly limited, but from the viewpoint of suppressing warping of the resulting laminate, it is preferably 60 to 90 parts by mass per 100 parts by mass of the nonvolatile components constituting the thermosetting resin composition, more preferably 60 to 80 parts by mass when the inorganic filler is a silica filler, and more preferably 70 to 90 parts by mass when the inorganic filler is an alumina filler or a BN filler.

[0115] Examples of black pigments include carbon and titanium, with carbon being more preferred from the viewpoint of easily obtaining superior hiding power. The content of the black pigment is not particularly limited, but from the viewpoint of easily ensuring hiding power, it is preferably 0.05 parts by mass to 3 parts by mass per 100 parts by mass of the non-volatile components of the thermosetting resin composition containing the black pigment.

[0116] Second Base Film 16 Examples of materials constituting the second base film 16 include polyolefin resins such as polypropylene resin and polymethylpentene resin, polyester resins such as polyethylene terephthalate resin and polyethylene naphthalate resin, polyimide resin, and polyetherimide resin. The second base film 16 may be a single-layer film composed of only one type of resin material, or a multilayer film composed of two types of films. However, when the second base film 16 is composed of a multilayer film, the adhesive strength between each film constituting the multilayer structure of the second base film 16 is set to be sufficiently greater than the peel strengths P1, P2, and P3 so that peeling does not occur at the interface between the films when an external force is applied to the multilayer sheet 100 in the thickness direction at the peeling portion P or the like. The second base film 16 may be a single-layer film or a multilayer film combining two or more types of films. It is also preferable that only one surface of the second base film 16 is release-treated with a release agent or the like. In this case, when producing the multilayer sheet 100, the release-treated surface of the second base film 16 is brought into close contact with the adhesive film 14. Examples of the release material include silicone-based release materials, long-chain alkyl-based release materials, and fluorine-based release materials. The thickness of the second base film 16 is not particularly limited, but from the standpoints of cost, processability, etc., it is preferably 15 μm to 100 μm, and more preferably 20 μm to 75 μm.

[0117] Third Substrate Film 18 The material and layer structure of the third substrate film 18 are not particularly limited. For example, the third substrate film 18 may have the same or similar material and layer structure as the second substrate film 16. However, from the viewpoint of easily satisfying formula (1), a self-adhesive film (adhesive film) is typically preferred. In this case, the self-adhesive property is imparted to the surface of the third substrate film 18 that comes into close contact with the second substrate film 16. When the third substrate film 18 is an adhesive film, the third substrate film 18 may be any film that includes an adhesive layer and a base layer, such as an adhesive film having a two-layer structure in which an adhesive layer and a base layer are laminated in this order. Furthermore, the adhesive strength between the adhesive layer and the base layer is set to be sufficiently greater than the peel strengths P1, P2, and P3 so that peeling does not occur at the interfaces of the layers that make up the adhesive film when an external force that divides the multilayer sheet 100 in half in the thickness direction is applied at the peeling portion P or the like.

[0118] The pressure-sensitive adhesive layer preferably has adhesive strength at room temperature and sufficient adhesion to an adherend such as the second base film 16. Examples of materials constituting the pressure-sensitive adhesive layer include acrylic resins, various synthetic rubbers, natural rubbers, and polyimide resins.

[0119] The substrate layer may be a known resin film, such as a plastic film such as a polyester film, a polytetrafluoroethylene film, a polyethylene (PE) film, a polypropylene film, or a polymethylpentene film. Among these, a polyester film is preferred, and a polyethylene terephthalate film is more preferred. The substrate layer may also be a laminate film formed by laminating two of the above-listed resin films. However, the adhesive strength between the resin films constituting the laminate film is set to be sufficiently greater than the peel strengths P1, P2, and P3 so that peeling does not occur at the interface between the resin films constituting the laminate film when an external force is applied to the multilayer sheet 100 in the thickness direction, such as at the peeling portion P.

[0120] Examples of adhesive films include PET-type adhesive films consisting of a PET film and an adhesive layer provided on at least one side of the PET film, EVA-type adhesive films consisting of an EVA (ethylene-vinyl acetate copolymer resin) film and an adhesive layer provided on at least one side of the EVA film, and OPP-type adhesive films consisting of an OPP (biaxial centrifugal polypropylene resin) film and an adhesive layer provided on at least one side of the OPP film. PET-type adhesive films are preferred from the viewpoint of ensuring easy rigidity. The thickness of the adhesive film is not particularly limited, but is preferably 25 μm to 100 μm from the viewpoints of cost and preventing wrinkles when tension is applied horizontally to the multilayer sheet 100, and more preferably 30 μm to 75 μm from the viewpoint of ease of handling.

[0121] In addition, when a semiconductor device is manufactured as a final product by performing further post-processing on a laminate produced using the multilayer sheet 100 of this embodiment, the third base film 18 may function as a backgrind tape.

[0122] Manufacturing Method of Multilayer Sheet 100 The manufacturing method of the multilayer sheet 100 of this embodiment is not particularly limited, and the multilayer sheet 100 can be appropriately manufactured, for example, by the following procedures (i) and (ii). (i) First, a coating liquid for forming the adhesive film 14 is applied to one side of the first base film 12, followed by drying to form the adhesive film 14. Next, a second base film 16 is laminated onto the adhesive film 14, and further, a third base film made of a pressure-sensitive adhesive film is laminated onto the second base film 16. (ii) First, a coating liquid for forming the adhesive film 14 is applied to one side of the second base film 16, followed by drying to form the adhesive film 14. Next, the first base film 12 is laminated onto the adhesive film 14, and the third base film made of a pressure-sensitive adhesive film is laminated onto the second base film 16.

[0123] The coating liquid for forming the adhesive film 14 is prepared by dissolving the thermosetting resin composition that constitutes the adhesive film 14 in a solvent to prepare a solution having a viscosity suitable for coating. The method for applying the coating liquid is not particularly limited, and for example, a roll coater or the like can be used.

[0124] Uses of the Multilayer Sheet 100 The multilayer sheet 100 of this embodiment can be used in lamination processes and post-processing to form a laminate or to further manufacture a final product from the laminate, similar to the conventional multilayer sheet 10. However, the multilayer sheet 100 of this embodiment is particularly suitable for use in manufacturing various semiconductor devices as final products. In this case, the member to be laminated 200 can be a glass carrier substrate, a semiconductor wafer, or the like, depending on the manufacturing process of the semiconductor device.

[0125] Specific examples of the present invention will be described below with reference to examples, but the present invention is not limited to the examples described below.

[0126] 1. Films and Coating Liquids for Producing Multilayer Sheets The films and coating liquids used in producing the multilayer sheets of the Examples and Comparative Examples were as follows.

[0127] (1) First Base Film D-1: PET film with one release-treated surface (pure water contact angle: 102°, 31B tape peel strength: 115 mN / 25 mm, thickness: 25 μm, elastic modulus Q1: 3500 MPa) D-2: PET film with one release-treated surface (pure water contact angle: 115°, 31B tape peel strength: 275 mN / 25 mm, thickness: 25 μm, elastic modulus Q1: 3500 MPa) D-3: PP film with one release-treated surface (pure water contact angle: 110°, 31B tape peel strength: 125 mN / 25 mm, thickness: 25 μm, elastic modulus Q1: 1700 MPa) D-4: PET film with release treatment on one side (pure water contact angle: 89°, 31B tape peel strength: 4125 mN / 25 mm, thickness: 38 μm, elastic modulus Q1: 3500 MPa)

[0128] Here, "pure water contact angle" refers to the contact angle of pure water on the release-treated surface of the first base film. Furthermore, "31B tape peel strength" refers to the peel strength when 31B tape (manufactured by Nitto Denko) is attached to the release-treated surface of the first base film and then peeled at a peel speed of 300 mm / min and a peel angle of 180°. These points also apply to the second base film described below.

[0129] (2) Coating liquid C-1 for forming adhesive film: A coating liquid obtained by dissolving 76 parts by mass of nonvolatile components having the following composition in 24 parts by mass of an organic solvent. Nonvolatile component composition: 30 parts by mass of epoxy resin, 1.2 parts by mass of curing agent, 0.8 parts by mass of carbon, 68 parts by mass of silica filler. Elastic modulus R of the film (thickness 20 μm) obtained by applying and drying the coating liquid: 1.5 MPa

[0130] C-2: A coating liquid prepared by dissolving 86 parts by mass of nonvolatile components having the following composition in 14 parts by mass of an organic solvent. Nonvolatile component composition: 23 parts by mass of epoxy resin, 1 part by mass of curing agent, 76 parts by mass of silica filler. Elastic modulus R of a film (thickness 20 μm) obtained by applying and drying the coating liquid: 2.5 MPa

[0131] C-3: A coating liquid prepared by dissolving 87 parts by mass of nonvolatile components having the following composition in 13 parts by mass of an organic solvent. Nonvolatile component composition: 23.9 parts by mass of epoxy resin, 1 part by mass of curing agent, 0.1 part by mass of carbon, 75 parts by mass of silica filler. Elastic modulus R of a film (thickness 20 μm) obtained by applying and drying the coating liquid: 3.0 MPa

[0132] C-4: A coating liquid prepared by dissolving 89 parts by mass of nonvolatile components having the following composition in 11 parts by mass of an organic solvent. Nonvolatile component composition: 13.4 parts by mass of epoxy resin, 0.5 parts by mass of curing agent, 0.6 parts by mass of carbon, 85.5 parts by mass of alumina filler. Elastic modulus R of a film (thickness: 20 μm) obtained by applying and drying the coating liquid: 3.5 MPa

[0133] (3) Second base film B-1: PET film with one release-treated surface (pure water contact angle: 96°, 31B tape peel strength: 2313 mN / 25 mm, thickness: 38 μm, elastic modulus Q2: 3500 MPa) B-2: PET film with one release-treated surface (pure water contact angle: 94°, 31B tape peel strength: 688 mN / 25 mm, thickness: 38 μm, elastic modulus Q2: 3500 MPa) B-3: PET film with one release-treated surface (pure water contact angle: 96°, 31B tape peel strength: 2313 mN / 25 mm, thickness: 25 μm, elastic modulus Q2: 3500 MPa) B-4: B-1: PET film with release treatment on one side (pure water contact angle: 89°, 31B tape peel strength: 4125 mN / 25 mm, thickness: 38 μm, elastic modulus Q2: 3500 MPa) B-2: PET film with release treatment on one side (pure water contact angle: 73°, 31B tape peel strength: 7500 mN / 25 mm, thickness: 38 μm, elastic modulus Q2: 3500 MPa) B-3: PET film with release treatment on one side (pure water contact angle: 102°, 31B tape peel strength: 115 mN / 25 mm, thickness: 25 μm, elastic modulus Q2: 3500 MPa) B-4: PET film with release treatment on one side (pure water contact angle: 102°, 31B tape peel strength: 115 mN / 25 mm, thickness: 25 μm, elastic modulus Q2: 3500 MPa) B-5: PET film with release treatment on one side (pure water contact angle: 89°, 31B tape peel strength: 4125 mN / 25 mm, thickness: 38 μm, elastic modulus Q2: 3500 MPa) B-6: PET film with release treatment on one side (pure water contact angle: 102°, 31B tape peel strength: 115 mN / 25 mm, thickness: 25 μm, elastic modulus Q2: 3500 MPa) PP film with release treatment on one side (pure water contact angle: 110°, 31B tape peel strength: 125 mN / 25 mm, thickness: 25 μm, elastic modulus Q2: 1700 MPa)

[0134] (4) Third base film A-1: ​​Film having a pressure-sensitive adhesive layer on one side of a base layer (PET film) (180° peel strength against 188 μm polyester: 0.17 N / 25 mm, total thickness: 50 μm, elastic modulus Q3: 3500 MPa) A-2: Film having a pressure-sensitive adhesive layer on one side of a base layer (PET film) (180° peel strength against 188 μm polyester: 0.20 N / 25 mm, total thickness: 38 μm, elastic modulus Q3: 3500 MPa) A-3: Film having a pressure-sensitive adhesive layer on one side of a base layer (PET film) (180° peel strength against 188 μm polyester: 0.49 N / 25 mm, total thickness: 50 μm, elastic modulus Q3: 3500 MPa) A-4: A-5: A film having an adhesive layer on one side of a base layer (PET film) (180° peel strength against 188 μm polyester: 1.23 N / 25 mm, total thickness: 50 μm, elastic modulus Q3: 3500 MPa) A-6: A film having an adhesive layer on one side of a base layer (PE film) (180° peel strength against 188 μm polyester: 0.08 N / 25 mm, total thickness: 50 μm, elastic modulus Q3: 3500 MPa) A-7: A film having an adhesive layer on one side of a base layer (PE film) (180° peel strength against 188 μm polyester: 0.13 N / 25 mm, total thickness: 70 μm, elastic modulus Q3: 1000 MPa)

[0135] Here, the term "180° peel strength against 188 μm polyester" refers to the peel strength measured when a polyester film (thickness: 188 μm) is attached to the surface of the third base film on which the pressure-sensitive adhesive layer is provided using a roller, and then the film is left at room temperature for 30 minutes, after which it is peeled off at a peel speed of 300 mm / min and a peel angle of 180°.

[0136] 2. Preparation of Multilayer Sheets Next, as shown in Tables 1 to 3, multilayer sheets of each Example and Comparative Example were prepared by combining a first substrate film, a coating liquid for an adhesive film, a second substrate film, and a third substrate film. Specifically, in preparing the multilayer sheets, the coating liquid for the adhesive film was first applied to one side (the release-treated side) of the first substrate film using a roll coater, and then dried to form an adhesive film (20 μm thick). Next, a second substrate film was bonded to the surface of this adhesive film. In this case, the release-treated side of the second substrate film was bonded to the surface of the adhesive film. Then, the surface of the third substrate film on which the adhesive layer was provided was bonded to the surface of the second substrate film to prepare a strip-shaped multilayer sheet.

[0137] 3. Evaluation Results The results of evaluation of peel defects for the multilayer sheets of each Example and Comparative Example, along with the type of each film constituting the multilayer sheet and the property values ​​of the multilayer sheet (peel strength, elastic modulus, etc.), are shown in Tables 1 to 3. The results of evaluation of the hiding property (L value) for the multilayer sheets of some Examples are shown in Table 4. Details of the evaluation methods for peel strength, elastic modulus, peel defects (processability, releasability, lamination), and hiding property (L value) shown in the tables are explained in Section 4 below.

[0138]

[0139]

[0140]

[0141] 4. Evaluation Methods For the multilayer sheets of each Example and Comparative Example, the peel strengths P1, P2, and P3 were measured, and the modulus of elasticity of each film constituting the multilayer sheet was also measured. Furthermore, using the multilayer sheets of each Example and Comparative Example, peel failure was evaluated when lamination processing was performed using the continuous processing method shown in Figure 1. Details of these evaluation methods are described below.

[0142] 4.1 Measurement of Peel Strength (1) Measurement of Peel Strength P1 Using a measurement sample obtained by cutting the multilayer sheet to a width of 250 mm and a length of 250 mm, peel strength P1 was measured using an autograph (Shimadzu Science Autograph AGS-X (load cell: 5N)). For the measurement, the measurement sample was fixed to a flat-surfaced sample stage with the side on which the first base film was provided facing up, and one end of the longitudinal direction of the sample was set to 0°. Starting from one end of the measurement sample as the peel initiation point, the first base film was peeled in a 180° direction (toward the other end) (i.e., at a peel angle of 180°) at a peel speed of 500 mm / min. The peel strength at this time was then measured. Peel strength measurements were performed on five measurement samples, and the average of the five measured strengths was calculated as peel strength P1.

[0143] (2) Measurement of Peel Strength P2 The first base film was removed from the multilayer sheet to expose the surface of the adhesive film. Next, a peel-assisting PET film (thickness: 25 μm, no release treatment on both sides of the film) was attached to the exposed surface of the adhesive film using a laminator at a temperature of 80 °C and a lamination speed of 0.3 m / min to assist in peeling at the interface between the second base film and the adhesive film, thereby obtaining a laminate. Next, the obtained laminate was cut into a measurement sample with a width of 250 mm and a length of 250 mm, and the peel strength P2 was measured using an autograph. During the measurement, the measurement sample was fixed to a flat-surfaced sample stage with the side on which the peel-assisting PET film was provided facing up, and one end of the longitudinal direction of the measurement sample was set to 0°. Using one end of the measurement sample as the peel starting point, the two-layer film (the peel-assisting PET film and the adhesive film) was peeled in a 180° direction (toward the other end) at a peel speed of 500 mm / min. The peel strength at this time was then measured. The peel strength was measured for five samples, and the average value of the five measured strengths was determined as the peel strength P2.

[0144] (3) Measurement of Peel Strength P3 After removing the first base film and adhesive film from the multilayer sheet, the multilayer sheet was cut into a 250 mm wide and 250 mm long sample. The peel strength P3 of the resulting sample was measured using an autograph. The measurement sample was fixed to a flat sample stage with the side on which the third base film was provided facing up, and one end of the longitudinal direction of the sample was set at 0°. Starting from one end of the sample as the peel initiation point, the third base film was peeled in a 180° direction (toward the other end) at a peel speed of 500 mm / min. The peel strength at this time was then measured. The peel strength measurement was performed on five samples, and the average of the five measured strengths was calculated as the peel strength P3.

[0145] 4.2 Measurement of Elastic Modulus For the first base film, second base film, and third base film used in the preparation of the multilayer sheet, test pieces 25 mm wide x 23 cm long were cut out from each film. Furthermore, when measuring the elastic modulus of the adhesive film, an adhesive film was applied to a PET film and dried under the same conditions as when the multilayer sheets of each Example and Comparative Example were prepared, and then peeled off from the PET film to cut out a test piece 25 mm wide x 23 cm long. Next, the elastic modulus of the test piece was measured using a Shimadzu Science Autograph AGS-X (load cell: 5 kN) in accordance with JIS K7127 (1999) under the conditions of a measurement temperature of 23±2°C, 50±5% RH, and a pulling speed of 5 mm / min.

[0146] 4.3 Evaluation of Peeling Defects (1) Evaluation of Processability (Evaluation of Insufficient Peeling Occurring in the Second Region Peeling Step) The lamination process (first process) shown in Figure 1 was performed using the multilayer sheets of each Example and Comparative Example. However, during the lamination process, the second step (laminate formation step) was not performed on the laminated portion R, and only the sheet main body portion was collected. This test was performed 100 times, and 100 sheet main bodies obtained were visually observed. Those with insufficient peeling (peel defects in which the film constituting the second region 10R2, which should not be present in the sheet main body portion, still remained) were judged as defective. The percentage of non-defective products (non-defective product rate (%)) among the 100 sheet main bodies was then calculated. <Notes> The multilayer sheets of each Example and Comparative Example 1 were all four-layer multilayer sheets. Here, "non-defective products" in the four-layer multilayer sheet refers to the sheet main body portion 100A1 having the cross-sectional structure shown in Figure 5(a). Furthermore, in a four-layer multilayer sheet, a "defective product" means a state in which the adhesive film 14 and the second base film 16 still remain in the second region 10R2 in the sheet main body portion 100A1 shown in Figure 5(a), which in the case of a conventional three-layer multilayer sheet 10 would correspond to a state in which poor peeling has occurred, as illustrated in Figure 16(a).

[0147] (2) Evaluation of Peelability (Evaluation of Excessive Peeling Occurring in the First Step) The lamination process (first process) shown in FIG. 1 was performed using the multilayer sheets of each Example and Comparative Example. However, during the lamination process, the second step (laminate formation step) was not performed on the laminated portion R, and only the sheet main body portion was collected. In the longitudinal direction of the obtained sheet main body portion, assuming a 100% non-defective product rate, a section where 100 consecutive first regions 10R1 were formed (a section equivalent to 100 first regions 10R1 formed by half-cutting) was visually observed to determine whether excessive peeling (a peeling defect in which the film constituting the first region 10R1 that should be present in the sheet main body portion was not present) occurred in the 100 first regions 10R1. The total number of sections (non-defective products) where no excessive peeling occurred was then counted, and the percentage of non-defective products (non-defective product rate (%)) was calculated. <Notes> The multilayer sheets of each Example and Comparative Example 1 are all four-layer multilayer sheets. Here, a "good product" in a four-layer multilayer sheet refers to a sheet body 100A1 having the cross-sectional structure shown in Fig. 5(a). Furthermore, a "defective product" in a four-layer multilayer sheet refers to a state in which the adhesive film 14 that should be present in the first region 10R1, or the adhesive film 14 and the second base film 16, are not present in the sheet body 100A1 shown in Fig. 5(a). In the case of a conventional three-layer multilayer sheet 10, this corresponds to a state in which a peeling defect occurs, as shown in Fig. 17(a).

[0148] (3) Evaluation of lamination properties (evaluation of wrinkle-induced peeling occurring in the second step) The lamination process (first process) shown in Fig. 1 was carried out using the multilayer sheet of each example. Note that a glass substrate having the same shape and size as the first region 10R1 was used as the member to be laminated 200. The laminated body obtained after passing through the laminating section R (a laminated body in which the third base film 18, the second base film 16, the adhesive film 14, and the member to be laminated 200 are laminated in this order) was further subjected to a peeling process in which a peel tape was attached to the surface of the laminated body on which the member to be laminated 200 was provided, and then the peel tape was pulled downward to cause peeling at the interface with the smallest peel strength (the interface between the adhesive film 14 and the second base film 16), thereby separating the laminated body into a member in which the third base film 18 and the second base film 16 were laminated (a sheet-unnecessary portion) and a member in which the adhesive film 14 and the member to be laminated 200 were laminated (a main body portion of the laminated body). Then, for the 100 laminate body main parts obtained after the peeling process, when the side on which the adhesive film 14 was provided was visually observed, if the surface of the adhesive film 14 was exposed, it was judged to be a "good product," and if the second base film 16 with wrinkles on the surface was further attached to the adhesive film 14 (wrinkle-induced peeling), it was judged to be a "defective product," and the percentage of good products (good product rate (%)) was calculated.

[0149] 4.4 Evaluation of Concealment Ability (L Value) An adhesive film was formed by applying the coating liquid for forming the adhesive film used in each Example and Comparative Example to the surface of a 1 mm thick PET film and then drying it. In this case, the thickness of the adhesive film formed on the PET film was set to be the same as the thickness of the adhesive film constituting the multilayer film of each Example and Comparative Example. Next, the lightness L value in the Lab color system of the adhesive film formed on the surface of the PET film on white clean paper was measured. The lightness L value was measured using a spectrophotometer (NF999 SPECTRO PHOTOMETER, manufactured by NIPPON DENSHOKU) with measurement mode: color difference meter and measurement conditions: C / 2°. The evaluation criteria are as follows: A: L value is 20 or less; B: L value is more than 20 and less than 50; C: L value is 50 or more.

[0150] 10: Multilayer sheet 10A, 10A1, 10A2, 10A2': Sheet main body portion 10B, 10B1, 10B2: Sheet unnecessary portion 10C: Half-cut surface 10N: Non-half-cut surface 10R1: First region 10R2: Second region 12: First base film 14: Adhesive film 16: Second base film 18: Third base film 20: Support roll 22: Half-cut roll 30: Peeling claw 30S1: First support surface 30S2: Second support surface 30T: Tip portion 32: Support roll 40: Support roll 50: Pressure roll 52: Pressure roll 60: Peeling tape 100: Multilayer sheet 100A, 100A1, 100A2, 100A2': Sheet main body portion 100B, 100B1, 100B2: Sheet unnecessary portion 200: Lamination target material CL: Cutting line HC: Half cut portion P: Peeling portion R: Laminated portion

Claims

1. A multilayer sheet comprising a first base film, an adhesive film, a second base film, and a third base film, the first base film, the adhesive film, the second base film, and the third base film being laminated in this order, and satisfying the following formula (1): Formula (1) P1<P2<P3 (In the formula (1), P1 represents the peel strength (N / 250 mm) between the first base film and the adhesive film, P2 represents the peel strength (N / 250 mm) between the adhesive film and the second base film, and P3 represents the peel strength (N / 250 mm) between the second base film and the third base film.) 2. The multilayer sheet according to claim 1, which satisfies the following formula (2): Q2 / Q3≦2.0 (in formula (2), Q2 represents the elastic modulus (MPa) of the second base film, and Q3 represents the elastic modulus (MPa) of the third base film).

3. The multilayer sheet according to claim 1 or 2, wherein the peel strength P3 is 0.5 N / 250 mm to 15 N / 250 mm.

4. A multilayer sheet according to any one of claims 1 to 3, wherein the peel strength P2 is greater than 0.1 N / 250 mm and not more than 5 N / 250 mm.

5. A multilayer sheet according to any one of claims 1 to 4, wherein the peel strength P1 is 0.1 N / 250 mm or more and less than 5 N / 250 mm.

6. The multilayer sheet according to any one of claims 1 to 5, wherein the third base film comprises a PET film and an adhesive layer provided on one side of the PET film.

7. A multilayer sheet according to any one of claims 1 to 6, wherein the surface of the second base film that comes into close contact with the adhesive film is release-treated.

8. The multilayer sheet according to any one of claims 1 to 7, wherein the adhesive film is made of a resin composition containing an epoxy resin, a curing agent, an inorganic filler, and a black pigment.

9. The multilayer sheet according to any one of claims 1 to 8, wherein the surface of the first base film that comes into close contact with the adhesive film is release-treated.

10. The multilayer sheet according to any one of claims 1 to 9, which is used in the manufacture of a semiconductor device.

11. A half-cutting process for partially cutting the multilayer sheet according to any one of claims 1 to 10 from the surface of the multilayer sheet on which the first base film is provided halfway through the thickness direction of the multilayer sheet so as to separate the first base film, the adhesive film and the second base film, and simultaneously dividing the surface of the multilayer sheet on which the first base film is provided into a first region and a second region other than the first region, with a cutting line formed by the cutting as a boundary line; a second region peeling process for peeling the second region at the interface between the second base film and the third base film; and a first process for peeling the first region at the interface between the first base film and the adhesive film. a second step of forming a laminate by heating and pressurizing a laminate obtained by bonding a member to be laminated to a surface of the adhesive film of a sheet main body portion in which the second base material film and the adhesive film are laminated in this order on one side of the third base material film and in the first region, the sheet being one of two sheets obtained by separating the multilayer sheet into two in its thickness direction by at least undergoing the second region peeling step and the first step.

12. The method for producing a laminate according to claim 11, wherein the first step is carried out after the second region peeling step is carried out.

13. The method for producing a laminate according to claim 11, wherein the second region peeling step and the first step are carried out substantially simultaneously.

14. The method for producing a laminate according to any one of claims 11 to 13, wherein the multilayer sheet is a strip-shaped sheet.

15. The method for producing a laminate according to claim 14, wherein the first region is a plurality of circular or substantially circular regions arranged along the longitudinal direction of the multilayer sheet.

16. The method for producing a laminate according to claim 15, wherein the member to be laminated is a semiconductor wafer or a glass wafer.

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