JPH0572858B2 - - Google Patents

Abstract

PURPOSE:To secure the transmission of super-sonic oscillation to a welding sheet and to simplify an apparatus for the carry-in or the carry-out of a welding article, by making a plane where the horn and the anvil of super-sonic oscillator contact the welding sheet into a specific shape. CONSTITUTION:The side faces of convex parts 5, 5 provided at planes 3, 3 where the horn 1 and the anvil 2 of a super-sonic oscillation contact a welding sheet are inclined at theta degrees and becomes inclined slopes 6. By making the convex parts 5, 5 into trapezoid forms by providing such inclined slopes 6, when multi-layered sheets are welded each other, the convex parts 5 bite into the above-mentioned sheet and transmit super-sonic oscillation certainly deep into the multi-layered sheets, whereby sufficient melting and firm welding can be done. Furthermore as it is possible to transmit super-sonic oscillation certainly to the welding plane, an apparatus to support firmly under interposing used formerly becomes unnecessary, and it can be done only with a conveyer to carry-in or carry-out a welding article 17.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an ultrasonic sealing device for sealing the bottom of a tube container. [Prior art and its problems] Ultrasonic sealing devices that weld a pair of sheet materials together using ultrasonic vibrations include so-called longitudinal vibration type devices that apply ultrasonic vibrations in a direction perpendicular to the welding surface; The so-called transverse vibration type, which applies ultrasonic vibration in a direction parallel to the plane, was developed by the applicant of the present invention in Japanese Patent Application No. 56-123692 (Japanese Unexamined Patent Publication No. 58-33424).
No.) and Japanese Patent Application No. 1987-87765 (Japanese Unexamined Patent Publication No. 58-205723)
There are three types of diagonal vibration type proposed in No. 1, which applies ultrasonic vibration diagonally to the welding surface. Looking at the characteristics of each of these three types, the longitudinal vibration type applies vibration in a direction perpendicular to the welding surface, so a so-called lateral slip phenomenon occurs between the horn and anvil and the sheet material to be welded. However, since vibration is applied in a direction perpendicular to the welding surface, when welding the bottom of a tube container, even if the filling inside the container is attached to the welding surface, the vibration will cause the filling to move out of the welding surface. Therefore, it is not suitable for welding the bottom of a tube container containing cosmetics or the like. On the other hand, the transverse vibration type and diagonal vibration type have the ability to scatter the filler adhering to the welding surface to the outside of the welding surface by vibration, so they have traditionally been used for sealing the bottom of tube containers. It is used. However, with the transverse vibration type, since vibration is applied in a direction parallel to the welding surface, a side-slip phenomenon occurs between the horn and anvil and the sheet material held by them, and the vibrations cause the vibration to be applied to the welding surface. The horn may generate heat due to the heat being not transmitted efficiently to the horn, the frictional heat generated by vibration may not be sufficiently generated, resulting in poor welding, or an unpleasant high-pitched sound may be generated due to sideways slipping. There is a problem that hangnails or scrapes may occur on the surface of the sheet material that is in contact with the material. Therefore, a concavo-convex pattern as shown in FIG. 12 is engraved on the contact surface of the horn and anvil with the sheet-like material, but very good results have not been obtained with the concave-convex pattern shown in FIG. In addition, with the diagonal vibration type, the vibrations are dispersed in the vertical and horizontal directions, so it has the advantages of both the vertical vibration type and the horizontal vibration type, and has the ability to blow away foreign substances attached to the welding surface in the horizontal direction. At the same time, it also has the effect of suppressing the lateral slip phenomenon to some extent, and can perform welding more efficiently than the lateral vibration type. Therefore, good results have been shown in the welding of multilayer sheets, which is not so good with the transverse vibration type. However, the fact remains that a side-slip phenomenon occurs, and this side-slip phenomenon cannot be eliminated even by carving a concave-convex pattern on the contact surface as shown in Fig. 12. Efficient welding is desired. By the way, in the conventional ultrasonic sealing device for sealing the bottom of a tube, before the bottom of the tube container is clamped between the horn and the anvil, the steps shown in FIGS.
After being clamped by a clamping device 20 called a jaw as shown in FIG. 6, the bottom of the tube container 17 is clamped between a horn 1 and an anvil 2 and welded. To explain this clamping device 20, a sliding body 22 is slidably provided in a frame member 12, and this frame member 21 and sliding body 22 are connected to the bottom part of the tube.
The sliding body 22 is biased in the clamping direction by a spring 23 so as to clamp 7. A pair of guide plates 24 are vertically disposed diagonally between the lower part of the frame member 21 and the lower part of the sliding body 22, and guide the circular tube container 17 between the frame member 21 and the sliding body 22 so as to be flat. It's becoming like that. And the reason why we need such a device is
As mentioned above, since welding cannot be performed reliably with conventional sealing devices, such a clamping device 20 is
This is because it is necessary to clamp the bottom of the tube container 17 to assist in reliable welding.In addition, by clamping the bottom of the tube container 17, the molten resin generated on the welding surface during welding by ultrasonic vibrations does not flow into the tube container 17. This is to prevent the influx of However, the need for such a clamping device creates new problems. The first problem is that molten resin accumulates between the part held between the horn and the anvil and the part held by the holding device, and in this part
A bulge 25 as shown in FIG. 2 occurs, resulting in an extremely poor appearance. The second problem is that the presence of such a clamping device complicates the mass production line. That is, to explain a conventional sealing device having such a clamping device, as shown in FIG.
1, a turntable 32 having a plurality of clamping devices 20 around it, and a horn 1 and anvil 2 installed on one side of the turntable 32 to receive and carry out the sealed tube container 17. It is necessary to provide a carry-out conveyor 33, and the carry-in conveyor 31 and the carry-out conveyor 33
In order to transfer or receive the tube container 17 to the clamping device 20, a container holder 34 which also serves as a lifting device is required. If the clamping device 20 is removed, the container holder 34, which also serves as a lifting device, and the turntable 3
2 is no longer necessary, the carry-in conveyor 31 and the carry-out conveyor 33 can be formed by one conveyor, and an extremely simple mass production line can be formed. By the way, as a prerequisite for omitting such a clamping device, it is necessary to improve the uneven pattern carved on the contact surface of the horn and anvil to ensure reliable and strong welding. In order to reliably transmit ultrasonic vibrations, the contact surface parallel to the welding surface should be left as wide as possible on the horn or anvil, and the uneven pattern formed on the horn and anvil should be made to bite into it. Care must be taken to eliminate sideslip. The case where the contact surface parallel to the welding surface is maximum is when no uneven pattern is provided, but in this case, the degree of side slip is also maximum as described above. On the other hand, the case where the penetration of the uneven pattern is maximized is when the convex part and the tip are sharpened, but in this case, there is no contact surface parallel to the welding surface, so ultrasonic vibrations are transmitted to the welding surface. It is difficult to generate frictional heat. Considering the concavo-convex pattern shown in FIG. 12 from this point of view, this is because the diagonal intersecting grooves 4 form convex portions 5 having a rectangular planar shape, and the side surfaces of the convex portions 5 are vertically aligned. Since the surface 41 is formed, the convex portion 5 is difficult to bite into the sheet-like object, and side slipping cannot be reliably suppressed. Also, as another conventional example, Japanese Patent Application Laid-Open No. 60-201928

[Fig. 13a, b, c], a horn for ultrasonic sealing is formed by carving a plurality of uneven lines 42 with corners cut at a constant depth and protruding height along the longitudinal direction of the contact surface. Specifically, it is described that the uneven line 42 is a continuous uneven surface having a sinusoidal shape with no corners in the transverse cross section of the contact surface. However, it is clear from Figure 13a that the ultrasonic sealing device described in this publication is of the longitudinal vibration type (the vibration direction of the ultrasonic wave is in the axial direction of the horn, and the tip of the horn in the axial direction (It is understood that vibration is applied in a direction perpendicular to the welded surface of the sheet because of the contact surface provided.) Therefore, the uneven pattern to prevent side slipping is essentially unnecessary. Nevertheless, the purpose of providing the uneven stripes 42 is to hold the resin melted by ultrasonic vibration in a flowing position at the sealing portion, thereby increasing the welding ability. For example, even if this structure is used in a transverse vibration type or diagonal vibration type device, since the cross section of the uneven stripes 42 is sinusoidal, there is no contact surface parallel to the welding surface, and the frictional heat is not sufficiently absorbed. Irregular lines that do not occur and have dug in 4
2 also has little effect on sideslip. Against this background, the inventors of the present invention etched various uneven patterns on the contact surfaces of horns and anvils and repeated experiments. In order to ensure that the convex part bites into the sheet-like object, the contact surface parallel to the welding surface is at its maximum, i.e., when no convex part is provided.

[Fig. 11a] is the state where the convex part has maximum bite, that is, the tip of the convex part is sharpened.

[11th
Intermediate state with Figure b

It has been found that the method shown in FIG. 11c is the most effective. The present invention was made against this background, and an object of the present invention is to improve the uneven pattern to be engraved on the contact surface of the horn and anvil that clamp the tube container in an ultrasonic sealing device for sealing the bottom of the tube container. As a result, ultrasonic vibrations are efficiently transmitted to the sheet-like material, and welding is performed reliably and firmly.Thereby, the clamping device is omitted, and the entire ultrasonic sealing device is simplified. The technical challenge is to achieve this goal. [Means for Solving the Problems] In order to solve the above-mentioned technical problem, the present invention has a horn 1 and an anvil 2 that sandwich the bottom of a tube container made of thermoplastic resin, and generate ultrasonic vibrations. In an ultrasonic sealing device that welds the bottom of the tube container using frictional heat, the following technical measures were taken. Note that the ultrasonic sealing device in this case is limited to a transverse vibration type or an oblique vibration type, as a logical premise for the purpose of the present invention. The gist of the present invention is to form a plurality of convex portions 5 whose upper surfaces are flat by forming grooves 4 on each contact surface 3 of the horn 1 and anvil 2 that contact the bottom of the tube container 17, and to form a plurality of convex portions 5 whose upper surfaces are flat. The side surface of the convex part 5 is made into an inclined surface 6 so that the cross-section of
A conveyor is installed between the horn 1 and the anvil 2 to directly position the bottom of the tube container 17. First, the uneven pattern to be carved on each contact surface 3 of the horn 1 and anvil 2 will be described. The inclination angle θ of the inclined surface 6 of the convex portion 5 formed by the groove 4 needs to be changed somewhat depending on the material of the tube container 17 to be welded, but it is generally 5 to 5.
45 degrees, preferably 10-30 degrees. Further, grooves 4 for forming the plurality of convex portions 5 are provided.
It is conceivable that there are cases in which a straight pattern is carved so as to intersect with each other, and there are cases in which it is carved so as to form a curved pattern that is not straight. In the former case, as shown in Figures 7 and 8,
The rectangular or triangular convex portions 5 are formed in a continuous pattern, and in the latter case, a zigzag pattern or a wave pattern is formed when viewed from a plane, or the octagonal convex portions 5 are alternately formed as shown in Fig. 9. , a pattern in which hexagonal (honeycomb) convex portions 5 are continuously repeated (Fig. 3), and even circular convex portions 5
An example of this is the case where a pattern (FIG. 10) is formed in which the following steps are repeated. The size of the pattern formed by these grooves 4 and convex portions 5 is determined by taking into consideration the factors of generating more frictional heat, shortening the sealing time, and minimizing the pressing force by the horn 1 and the anvil 2. The distance l (pattern pitch) from one end of one convex part 5 to one end of another convex part 5 adjacent to it is 0.5 to 2.0.
mm, preferably 0.8 to 1.6 mm.
In addition, the shape and size of the convex portion 5 on the horn 1 side,
The shape and size of the convex portion 5 on the anvil 2 side may be made different. Furthermore, in order to obtain sufficient frictional heat, it is necessary to leave a certain amount of plane parallel to the welding surface.
For example, in the case of the honeycomb convex portion 5, the ratio of the ratio occupied by the grooves 4 to the proportion occupied by the flat surface of the upper surface of the honeycomb convex portion 5 is 30:70 to 64:36, preferably around 40:60. In addition, if the groove 4 for forming the convex part 5 is too deep, the convex part 5 will bite too deeply into the sheet of the tube container 17, such as when welding a tube container 17 made of thermoplastic resin, and the thickness of the welded part will increase. There is a risk that the groove may become thin and be torn off, and the
If the volume of the seal becomes too large, a large amount of molten resin will enter the seal, and if the resin solidifies, the appearance of the sealed portion will deteriorate. On the other hand, if the groove 4 is too shallow, the amount of bite of the convex portion 5 will be small, making it insufficient to suppress the side-slip phenomenon, and the efficiency of generating frictional heat at the welding surface will deteriorate. Therefore, the depth of the groove 4 is 35 times the thickness of one sheet of the tube container 17 to be welded.
~65%, preferably 40-60% is preferred. By the way, the grooves 4 on the horn 1 side and the grooves 4 on the anvil 2 side do not need to have the same depth.
One may be deeper than the other. By the way, tube containers to be welded by the ultrasonic sealing device of the present invention include a single layer sheet of thermoplastic resin, a multilayer sheet of thermoplastic resin, a thermoplastic resin layer and a sheet layer of other material other than synthetic resin such as paper or aluminum. It is molded from a multilayer sheet made of Regarding the use of multilayer sheets in tube containers, there are multilayer tubes in which the inner layer is high density polyethylene (HDPE) and the outer layer is low density polyethylene (LDPE), or between high density polyethylene and low density polyethylene. A multilayer tube with a gas barrier resin layer such as EVAL or nylon on top, and a multilayer sheet with sheet layers of different materials includes a multilayer tube with an aluminum laminate layer as an intermediate layer. Next, the entire apparatus of the present invention will be explained. First, let's talk about the case of an oblique vibration type ultrasonic sealing device.As shown in FIG. The oscillator 13, the amplifier 14, and the horn 1 are arranged and attached on the same axis, and ultrasonic vibrations are oscillated in the direction of this axis. The horn 1 has a pair of contact surfaces 3 on both sides of the tip, and each contact surface 3 is set so that the angle ψ with respect to the axis of the horn 1 is 5 to 40 degrees. This angle is preferably around 20 degrees. Then, the horn 1 and anvil 2 are installed so that they can move forward and backward so that the space between the horn 1 and anvil 2 can be opened and closed, or the horn 1 side is fixed and the anvil 2 side is movable forward and backward, or the anvil 2 side is fixed. Although it is conceivable to fix the horn 1 side and move it forward and backward, it is easiest to make the anvil 2 move forward and backward. Therefore, the driving means is preferably a hydraulic cylinder or the like. Also, when fixing horn 1,
Fix it so that the contact surface 3 of is upright. The anvil 2 can be set so that the contact surface 3 of the tip of the horn 1 and the contact surface 3 of the anvil 2 are separated by at least the diameter of the maximum tube container 17 in the retracted position. However, it is preferable for this interval to be narrower than the diameter of the tube container 17 for positioning during welding, and in reality, it is preferably about 5 to 15 mm. If this distance is greater than or equal to the diameter of the tube container 17, the tube container 17 can be directly positioned between the horn 1 and the anvil 2 and held and welded between the two. If the diameter is less than the diameter of the tube container 17, a guide 18 is required between the horn 1 and the anvil 2 to guide the tube container 17 from the side, as shown in FIG. In order to flatten the tube container 17, a pair of guide surfaces 19, 19 formed of a tapered surface or a convex arc surface are provided. Then, the tube container 17 is carried between the horn 1 and the anvil 2 from the guide 18 side, and the tube container 17 is carried in between the horn 1 and the anvil 2.
The tube container 17 is positioned between the horn 1 and the anvil 2 and is temporarily stopped, and a conveyor 15 for carrying out the tube container 17 after welding is installed below the horn 1 and the anvil 2. This conveyor 15 carries a tube container 17 from one side of the horn 1 and anvil 2 to the other side.
Since all you have to do is bring it in and take it out, you just have to install it in a straight line. Also, on the conveyor 15 is a holder 16 for holding the tube container 15 upside down.
are provided at regular intervals. Next, in the transverse vibration type ultrasonic sealing device, as shown in FIGS. 5 and 6, the axis connecting the ultrasonic oscillator 13, amplifier 14, and horn 1 is fixed upright, and A pair of parallel contact surfaces 3 are provided on both sides of the tip of the horn 1, and other points are the same as the oblique vibration type ultrasonic sealing device. In this case, ultrasonic vibrations vibrating in the axial direction of the horn 1 are applied via the contact surface 3 to the welding surface of the tube container 17 in a direction parallel to it. [Function] According to the present invention, since the side surface of the convex portion 5 provided on the contact surface 3 of the horn 1 and the anvil 2 is formed into an inclined surface 6, it is easy to bite into a sheet-like object. In particular, when welding multilayer sheets together, the protrusions 5 tend to dig into each other, so by appropriately selecting the height of the protrusions 5, that is, the depth of the grooves 4, welding the multilayer sheets together, as shown in Figure 4b, is possible. The convex portion 5 can penetrate into the inner layer of each layer of the sheet, which is the welding surface side.
Ultrasonic vibrations can be reliably transmitted to the welding surface, and frictional heat can be generated efficiently. In this respect, if the convex part 5 bites only into the outer layer, the ultrasonic vibrations will not be transmitted directly to the inner layer, but will be transmitted through the outer layer, and will be attenuated when transmitted from the outer layer to the inner layer. Therefore, sufficient frictional heat is not generated. In particular, when welding the bottom of a multilayer tube that has polyethylene layers as the inner and outer layers and an EVAL layer as the middle layer, the polyethylene layer and the EVAL layer are not bonded together due to the nature of the resin, so the convex part extends to the inner polyethylene layer. Welding was difficult with conventional means in which the protrusions 5 do not cut into the inner layer, but according to the present invention, the protrusions 5 cut into the inner layer, so welding can be performed satisfactorily. As a result, the conventionally required clamping device is not required, the structure of the device is simplified, and the entire process is simplified. Further, by forming the inclined surface 6, the cross section of the groove 4 itself also becomes trapezoidal, and the sheet-like material that has bitten into the groove 4 is likely to be peeled off from the pattern surface after welding. If the grooves 4 for forming the convex portions 5 are not straight but have a curved pattern, the resin melted by the ultrasonic vibrations is evenly distributed over the welding surface along the grooves 4. Therefore, there is no unevenness in the welding of the pair of sheet-like materials, and the welding can be performed reliably and firmly. This effect is most remarkable when the planar shape of the convex portion 5 formed by the curved pattern of grooves 4 is a honeycomb. In this regard, if the groove 4 is straight, the molten resin will flow in only one direction, and there will be parts with too little molten resin and parts with too much molten resin on the welding surface, resulting in uneven welding, and in the worst case, some parts will not be welded. There is a risk. Furthermore, in order to obtain sufficient frictional heat, it is necessary to leave a certain amount of plane parallel to the welding surface.
In the case of the present invention, since the upper surface of the convex portion 5 is left as a flat surface, there is no problem in this point. In addition, in the case of an oblique vibration type ultrasonic sealing device, by applying ultrasonic vibration from an oblique direction,
As mentioned above, even if the filler in the tube container is attached to the welding surface, the filler can be scattered outside the welding surface. By providing the convex portion 5 having an inclined surface 6, the effect of scattering the filler to the outside of the welding surface is more effectively performed. Therefore, welding can be performed even if cosmetics are still attached to the welding surface.
Furthermore, welding can be achieved by filling the tube container completely with cosmetic liquid and sealing it with the cosmetic liquid adhering to the welding surface. [Examples, Comparative Examples] Examples of the present invention will be described below while comparing them with comparative examples. Then, using the diagonal vibration type and horizontal vibration type ultrasonic sealing devices, tube containers 1 of various materials are sealed.
The bottom of No. 7 was sealed and the seal strength was measured, and the results are shown in Table 1. The uneven patterns formed on the contact surfaces 3 of the horn 1 and the anvil 2 are a honeycomb pattern shown in FIG. 1 and a conventional square pattern shown in FIG. 12. The pattern pitch l of the honeycomb-shaped uneven pattern used was 1.1 mm, and the ratio of the groove 4 to the plane on the convex part was 41:
59, the depth of groove 4 is 0.2 mm.

【table】

[Table] As is clear from Table 1, the one in which the honeycomb-shaped convex portion 5 is provided on the contact surface 3 seals better than the conventional one, especially when combined with an oblique vibration type ultrasonic sealing device. Very good results can be obtained when Since the side surface of the convex portion 5 was an inclined surface 6, the tube could be easily bitten into the tube, the unpleasant frictional noise generated during sealing was small, and the tube could be easily removed from the pattern surface after sealing. Since the combination of the oblique vibration type ultrasonic sealing device and the honeycomb-shaped convex portion 5 is good as described above, experimental data for this combination is shown in Table 2.

〔Effect of the invention〕

According to the present invention, the side surface of the convex portion provided on the contact surface between the horn and the anvil is made into an inclined surface so that it can easily bite into a sheet-like object, thereby suppressing the side-slip phenomenon as much as possible, thereby suppressing ultrasonic vibration. This technology reliably transmits frictional heat to the welding surface, efficiently generates frictional heat, and makes welding reliable and strong, eliminating the need for the clamping device that was previously required.
A tube container is carried in between the horn and anvil.
It can be a simple device that only includes a conveyor for carrying out, and the holder itself for holding the tube container does not need to have the function of a lifting device, so the cost of the entire device can be reduced. Moreover, it is possible to obtain the effect that the installation space can be small.

[Brief explanation of the drawing]

Fig. 1 is a front view of an oblique vibration type ultrasonic sealing device showing an embodiment of the present invention, Fig. 2 is a front view of the horn and anvil portion thereof, and Figs. A plan view and a sectional view showing an example,
Fig. 4a is a process diagram showing the process of sealing the bottom of a tube container, Fig. 4b is a sectional view showing the state of the convex part biting in, Fig. 5 is a front view of the transverse vibration type ultrasonic sealing device, Fig. 6 The figure is a front view of the horn and anvil portion, Figures 7 to 10 are plan views showing other examples of uneven patterns, Figure 11 is a sectional view showing the progress leading to the invention, and Figures 12 a and b are A plan view and a cross-sectional view showing a conventional uneven pattern; FIGS. 13a, b, and c are views showing a horn and its contact surface portion showing another conventional example; FIG. 14 is a conventional oblique vibration type ultrasonic sealing device FIGS. 15 and 16 are a sectional view and a perspective view of the jaw, and FIGS. 17a and 17b are views showing a sealing failure caused by a conventional device using a clamping device. DESCRIPTION OF SYMBOLS 1... Horn, 2... Anvil, 3... Contact surface, 4... Groove, 5... Convex part, 6... Inclined surface, 15
...conveyor.

Claims (1)

[Scope of Claims] 1. An ultrasonic sealing device in which the bottom of a tube container made of thermoplastic resin is held between a horn and an anvil, and the bottom of the tube container is welded using frictional heat generated by ultrasonic vibration, By forming grooves on each contact surface of the horn and anvil that contact the bottom of the tube container, a plurality of convex portions having flat upper surfaces are formed, and the convex portions are shaped so that the cross section of the convex portions is trapezoidal. A superstructure for sealing the bottom of a tube container, characterized in that the side surface is an inclined surface, and a conveyor is installed to position the bottom of the tube container between the horn and the anvil when the horn and the anvil are in an open state. Sonic sealing device. 2. The ultrasonic sealing device for sealing the bottom of a tube container according to claim 1, further comprising a guide provided between each contact surface of the horn and the anvil to flatten and guide the bottom of the tube container. 3. The ultrasonic sealing device for sealing the bottom of a tube container according to claim 1, wherein the grooves for forming the plurality of convex portions form a bent pattern. 4. The ultrasonic sealing device for sealing the bottom of a tube container according to claim 1, wherein the vibration direction of the ultrasonic wave is oblique to the welding surface of the bottom of the tube container. 5. The ultrasonic sealing device for sealing the bottom of a tube container according to claim 1, wherein the vibration direction of the ultrasonic wave is parallel to the welding surface of the bottom of the tube container. 6. The ultrasonic sealing device for sealing the bottom of a tube container according to claim 1, wherein the tube container is formed of a single layer sheet of thermoplastic resin. 7. The ultrasonic sealing device for sealing the bottom of a tube container according to claim 1, wherein the tube container is formed of a multilayer sheet of thermoplastic resin. 8. The ultrasonic sealing device for sealing the bottom of a tube container according to claim 3, wherein the planar shape of each convex portion formed by the groove is a honeycomb shape. 9. The ultrasonic sealing device for sealing the bottom of a tube container according to claim 3, wherein each convex portion formed by the groove has an octagonal planar shape. 10. The ultrasonic sealing device for sealing the bottom of a tube container according to claim 3, wherein each convex portion formed by the groove has a circular planar shape. 11. The ultrasonic sealing device for sealing the bottom of a tube container according to claim 7, wherein the multilayer sheet includes a sheet layer made of a thermoplastic resin and a different material.