WO2001039227A1

WO2001039227A1 - Laminate and method for producing the same

Info

Publication number: WO2001039227A1
Application number: PCT/JP2000/008217
Authority: WO
Inventors: Yoji Nagae; Shinichirou Ishida
Original assignee: Mitsubishi Plastics, Inc.
Priority date: 1999-11-22
Filing date: 2000-11-21
Publication date: 2001-05-31
Also published as: KR20020065528A; JP3883764B2; TW487632B; CN1391699A; JP2001150602A; CN1168109C; KR100480318B1

Abstract

A laminate comprising a soft layer (2), a first hard plastic layer (3), and a second hard plastic layer (4). The soft layer (2) has two surfaces, to one of which the first hard plastic layer (3) is bonded, and to the other of which the second hard plastic layer (4) is separably bonded.

Description

Description Laminated molded article and method for producing the same

The present invention relates to a laminated molded product and a method for producing the same. Laminated moldings include sealing materials incorporated into electronic equipment, touch panel surface materials for display-related products, or various non-slip materials. Background art

In recent years, there has been a demand for improving the feel and improving the anti-slip effect by covering the outer surface of an injection-molded article such as a keyboard, a normest and a mouse of a personal computer with a soft plastic layer. In addition, window holes are formed in injection molded articles such as control panels and boards for electrical appliances, and the window holes are covered with a plastic finolem, and the switch operation is performed by pushing the plastic finolem with a finger. There is something we can do. In this case as well, there is a demand for improving the softness of the portion touched by the finger and improving the anti-slip effect. Specifically, for example, Japanese Patent Application Laid-Open No. 4-215192 discloses a thin switch used in electronic equipment and the like as shown in FIGS. 8 (a) and 8 (b). A membrane switch is disclosed. In this membrane switch, the electrodes 3 la are formed on the upper sheet 32 a made of insulating resin, and the electrodes 31 b are formed on the lower sheet 32 b made of insulating resin by screen printing or the like. An insulating sheet 33 is provided between the electrode 31a and the lower sheet 32b. A hole 34 is formed between adjacent insulating sheets 33. As shown in Fig. 8 (b), the part of the upper sheet 32a corresponding to the hole 34 is When pressed in the direction shown in FIG. 2, the two electrodes 3 la and 31 b come into contact with each other to maintain the connection state of the switch. When the pressing on the upper sheet 32a is released, the upper sheet 32a returns to its original position due to its rigidity, and the connection of the switch is released. However, in the above configuration, there is no clicking feeling when the upper sheet 32a is pressed with a finger. Therefore, it cannot be confirmed whether or not both electrodes 31a and 31b are in contact. As shown in FIG. 9, Japanese Patent Laying-Open No. 7-52240 discloses a membrane switch provided with an embossed polyester resin embossed sheet 35. The embossed sheet 35 has a large number of convex portions 35 a (only one is shown). An insulation sheet 33 is sandwiched between the embossed sheet 35 and the lower sheet 32b. The electrode 31a is provided inside the convex portion 35a. A flexible top sheet 37 is provided at a position facing the lower sheet 32b via the insulating sheet 33, the embossed sheet 35 and the insulating layer 36. In the case of the membrane switch shown in Fig. 9, a click feeling is obtained, and it is possible to intuitively check whether the switch is on or off. However, since the pressing portion of the membrane switch is covered with the flat surface sheet 37, when operated by a blind touch, a pressing error occurs. Also, in the case of a membrane switch in which the top sheet 37 is removed to expose the projection 35a, the embossed sheet 35 is made of polyester resin (made of hard resin), so that the touch is hard and easy to slide. Further, since the electrode 31a is formed inside the projection 35a, the production of the switch becomes complicated. Disclosure of the invention

An object of the present invention is to provide a laminated injection-molded article that can be easily manufactured, suppresses surface slippage, and prevents a switch from being erroneously pressed, and a method for manufacturing the same. In order to achieve the above object, the present invention provides a soft layer and a first and a second hard plastic. The present invention provides a laminated molded article including a stick layer. The soft layer has two faces. The first hard plastic layer is adhered to one side of the soft layer. A second hard plastic layer is releasably attached to the other side of the soft layer. In the laminated molded product according to another aspect of the present invention, a hard plastic layer is adhered to one surface of the soft layer, and a film is laminated on the other surface so as to be peelable. The film is a hard plastic film. The film has a matte-coated surface, and the matte-coated surface is pressed against the other surface of the soft layer, so that the film can be peeled off from the soft layer. . A laminated molded article according to still another aspect of the present invention has an injection molded resin layer and a laminated film laminated on the injection molded resin layer. The laminated film includes a soft plastic layer and a hard plastic layer adhered to each other, and the soft plastic layer is disposed outside in a state where the laminated film is laminated on the injection molded resin layer. According to the method of manufacturing a laminated molded article of the present invention, first, a hard plastic layer is adhered to one surface of a soft plastic layer, and a protective layer is releasably laminated to the other surface of the soft plastic layer. Thereby, a laminated film is formed. Next, the protective layer of the laminated film is set toward the mold surface of the injection mold. Then, by injecting the molding material toward the hard plastic layer, an injection resin layer is formed on the hard plastic layer. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is a partially enlarged cross-sectional view of a laminated sheet according to a first embodiment of the present invention.

FIG. 1 (b) is a partially cutaway perspective view of the laminated sheet of FIG. 1 (a).

FIG. 2 is a partially enlarged sectional view of FIG.

FIG. 3 is a partially enlarged sectional view of the membrane switch sheet.

FIG. 4 is a partially enlarged cross-sectional view of the membrane switch. FIG. 5 is a cross-sectional view of the laminated sheet according to the second embodiment.

FIG. 6 is a cross-sectional view for explaining a method of manufacturing the laminated sheet of FIG. FIG. 7 is a partially enlarged cross-sectional view of the laminated sheet according to the third embodiment.

FIG. 8 (a) is a partially enlarged cross-sectional view of a conventional membrane switch.

FIG. 8B is a partially enlarged cross-sectional view showing a state where the switch of FIG. 8A is pressed. FIG. 9 is a partially enlarged cross-sectional view of another conventional membrane switch. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. As shown in FIGS. 1 (a) and 1 (b), a rectangular laminated sheet 1 includes a soft layer 2, a first hard plastic layer 3, and a protective film 4 made of a second hard plastic. Have. The first hard plastic layer 3 is firmly adhered to the lower surface of the soft layer 2 in FIG. Protective film 4 in FIG. 1 _(a), and is releasably laminated on the upper surface of the soft layer 2. A plurality of bulges 5 for a switch click are formed on the laminated sheet 1 at predetermined intervals, and are arranged in a matrix. The bulging portion 5 is formed to have substantially the same size as a hole 9a provided at a position corresponding to the electrodes 8a and 10a of the membrane switch 7 described later. The first hard plastic layer 3 is formed of a biaxially stretched polyethylene terephthalate film (biaxially stretched PET film). The soft layer 2 is formed of a crosslinked silicone rubber composition. The protective film 4 is made of a mat-coated biaxially stretched PET film. “The matte coating process is also called a matting process, in which fine irregularities are formed on the surface of the film, or a layer containing fine particles is applied. Will be described.

First, a bonding treatment is performed as necessary on a base film made of a biaxially stretched PET film having a predetermined thickness (for example, 12 m). Subsequently, the uncrosslinked silicone rubber composition is adhered onto the substrate film. The thickness of the silicone rubber composition is 30 μ IT! 〜150 μm is preferred. As the bonding treatment, for example, an undercoat layer is formed of a polyurethane resin or an amorphous polyester resin. A thermosetting thin film layer containing a silicone resin having a high affinity for the undercoat layer is formed on the undercoat layer. Examples of the silicone resin include a condensation type silicone resin. As the uncrosslinked silicone rubber composition, for example, an electron beam crosslinking type or electron beam curing type silicone elastomer which can crosslink the silicone rubber by irradiating an electron beam is used. The material of the silicone elastomer is mainly polydimethylsiloxane containing vinyl groups. As another material of the silicone elastomer, polydimethylsiloxane in which a part of methyl groups are substituted with phenyl group or trifluoropropyl group may be used. Subsequently, as shown in FIG. 2, a mat coat layer 4a is formed on the surface of the protective film 4 having a thickness of about 20 μm. The protective film 4 is pressed against the silicone rubber composition while the mat coat layer 4a is in contact with the silicone rubber composition, thereby forming a laminate comprising the base film, the silicone rubber composition, and the protective film 4. 6 is formed. Next, when the laminate 6 is irradiated with an electron beam, the silicone rubber composition is crosslinked, and the silicone rubber composition becomes the soft layer 2. The matte coat layer 4 a is disposed between the soft layer 2 and the protective finolem 4. The irradiation dose of the electron beam is preferably from 20 kGy to 150 kGy. Next, the laminate 6 is pressed into a predetermined shape by a press machine to form a laminate sheet 1 as shown in FIG. Next, a membrane switch using the laminated sheet 1 of FIG. 1 and a method of manufacturing the same will be described.

As shown in FIG. 4, the membrane switch 7 includes a main body 11. The main body 11 includes a base (print substrate) 8, a spacer 9 made of an insulating material, and an insulating sheet 1. 0 is provided. A plurality of electrodes 8a are arranged in a matrix on the base 8 at predetermined intervals. The spacer 9 has a hole 9a corresponding to each electrode 8a. The hole 9a accommodates the electrode 8a and the electrode 10a which forms a switch together with the electrode 8a. Then, a laminate composed of the second hard plastic layer 3 and the soft layer 2 from which the protective film 4 has been peeled off from the laminated sheet 1 is laminated on the main body 11. The bulging portion 5 of the laminate is disposed on the main body 11 at a position corresponding to each hole 9a. The soft layer 2 is located outside the bulging portion 5 and the hard plastic layer 3 is located inside the bulging portion 5. For example, the laminated sheet 1 is punched into a predetermined shape according to the key arrangement of the desktop computer, and then the first hard plastic layer 3 is bonded to the insulating sheet 10 of the main body 11. It is laminated on the main body 11. Thereafter, the protective film 4 is peeled off from the laminated sheet 1 to expose the soft layer 2, that is, the surface of the crosslinked silicone rubber. When the protective film 4 is peeled off, the fine uneven pattern of the surface of the mat coat layer 4a is transferred to the outer surface of the soft layer 2 of the membrane switch sheet 12. Therefore, a mat surface having fine irregularities appears on the surface of the soft layer 2. When the bulging portion 5 of the membrane switch 7 is pressed with a fingertip, the bulging portion 5 is depressed downward, the pressing force is transmitted to the insulating sheet 10, and the insulating sheet 10 bends toward the base 8. Then, the electrode 10a provided on the insulating sheet 10 is held in contact with the electrode 8a formed on the base 8, and the switch is turned on (on). When the pressing of the bulging portion 5 is released, the first hard plastic layer 3 returns to its original state due to its rigidity, and the switch is turned off. This embodiment has the following effects.

Compared with the case where the membrane switch sheet 12 is formed only of a hard PET film, the membrane switch sheet 12 of the present embodiment has The touch when touching the bulging portion 5 of the switch sheet 12 is soft, and the slip on the surface is suppressed, so that the switch can be prevented from being erroneously pushed. The soft layer 2 is formed of a crosslinked silicone rubber. Therefore, even when the membrane switch sheet 12 is stored or used at a relatively high temperature for a long period of time, it is hardly deteriorated, and as a result, the durability is improved. Since the silicone rubber composition is crosslinked by the electron beam, no heat is applied to the first hard plastic layer 3 and the protective film 4. Therefore, the first hard plastic layer 3 and the protective film 4 are not deteriorated by heat. The soft layer 2 made of silicone rubber reinforces the flexibility of the hard plastic layer 3. Therefore, compared to the case where only a hard plastic layer such as a PET film is used, a decrease in flexibility due to repeated pressing and release of the bulging portion 5 is suppressed, and durability is improved. When the laminated sheet 1 is press-formed, the protective film 4 protects the soft layer 2. Further, the soft layer 2 is reliably protected by the protective film 4 until the laminated sheet 1 is provided in the membrane switch 7. Therefore, the soft layer 2 is not damaged. When the swelling portion 5 is pressed, it becomes difficult to slip due to the fine irregularities formed on the surface of the soft layer 2. By peeling off the protective film 4 after the mat treatment, fine irregularities are transferred to the surface of the soft layer 2. Therefore, fine irregularities can be easily formed on the surface of the soft layer 2. Unlike the membrane switch using the embossed sheet 35 shown in FIG. 9, the membrane switch 7 of the present embodiment requires the electrodes to be formed on the laminated sheet 1. And manufacturing becomes easier. By stacking the membrane switch sheet 12 of the present embodiment on a membrane switch having a conventional structure without a click feeling as shown in FIGS. 8 (a) and 8 (b), a membrane having a click feeling is provided. The switch can be manufactured easily. Next, a second embodiment of the present invention will be described.

FIG. 5 is a front cross-sectional view showing a laminated molded body according to the second embodiment, and FIG. 6 is a front sectional view for explaining a method for manufacturing the laminated molded body of FIG. In the laminated molded article shown in FIG. 5, a hard plastic layer 22 is provided between the injection molded resin layer 44 and the soft plastic layer 21. The hard plastic layer 22 is firmly bonded to the injection molded resin layer 44, and the soft plastic layer 21 is disposed on the surface of the laminated molded body. A laminated film 45 is constituted by the hard plastic layer 22 and the soft plastic layer 21. In the present embodiment, the injection-molded resin layer 44 is formed by injecting a resin such as a high-impact polystyrene resin, an acrylonitrile-butadiene-styrene copolymer resin, or an acrylonitrile-styrene copolymer resin. It is obtained by molding. Silicone rubber is preferably used for the soft plastic layer 21 having elasticity. As the silicone rubber, an electron beam crosslinkable silicone rubber, a millable silicone rubber, a liquid curable silicone rubber or the like, which is composed of a composition containing polydimethylsiloxane as a main component, is preferable. Polydimethylsiloxane has dimethylsiloxane as the main monomer component. Other monomer components include one or two methyl groups (one or three at the end) as a bul group, a phenyl group, and a long chain. Alkyl group, fluoroalkyl group, hydroxy group (= silanol group), amino group, glycidyl group, alkoxy A monomer substituted with a group, chlorine, hydrogen or the like can be used. In addition to polydimethyl siloxane, fillers, vulcanizing agents, property improvers, etc. to assist with various properties of silicone, such as processability, heat resistance, mechanical properties, adhesion, flame retardancy or reliability You can add ingredients. As the filler, for example, silica, diatomaceous earth, quartz powder, calcium carbonate, silicone resin, bonbon and the like are used. As the vulcanizing agent, an organic peroxide, a modified silane, a modified siloxane, an alkoxysilane, a platinum compound or the like is used. As a reaction inhibitor for adjusting the curability, acetylene alcohol, cyclic methylvinylinolesiloxane, or the like is used. The property improver includes a processing aid, a heat resistance improver, a reversion inhibitor, a flame retardant, and an adhesion improver. As a processing aid, a low-viscosity silicone oil containing a terminal silanol group or a terminal alkoxy group, a silicone resin, or a silane compound is used. Metal oxides such as iron and nickel and metal organic acids are used as heat resistance improvers. Examples of the reversion inhibitor include acid acceptors such as calcium oxide and barium oxide. Flame retardants include platinum compounds, iron oxide, titanium oxide, and carbon. A silane coupling agent is used as the adhesion improver. The thickness of the soft plastic layer 21 is preferably 30 to 500 μπι. If it is less than 300 zm, it has an anti-slip effect, but its softness is somewhat insufficient. If it exceeds 500 μπι, the cost increases. As the hard plastic layer 22, a biaxially stretched film such as polyethylene terephthalate (PET), polypropylene (PP), or polystyrene (PS) is used. Among them, PET is most preferable as the material of the hard plastic layer 22 because the biaxially stretched polyethylene terephthalate film has high strength, high rigidity, and excellent click feeling and restoring force when used for a switch. As shown in FIG. 6, the injection mold 4 used for molding the laminated molded body is the first mold. 41 and a second molding die 46 are provided. Between the first molding die 41 and the second molding die 46, a projection 42 for forming a cavity 43 in the injection molding resin layer 44 is provided. Next, a method for producing a laminated sheet constituting a part of the laminated molded article will be described.

First, a primer having a polyurethane resin or an amorphous polyester resin as a main component is applied to a biaxially stretched PET film having a predetermined thickness, for example, a thickness of 12 μπι, and dried. An uncrosslinked silicone resin is laminated on the dried film. Subsequently, a protective layer 23 made of a biaxially stretched PET film having a thickness of 12 μm is pressed against the surface of the silicone resin using a rolling roll (not shown). At this time, the silicone resin is rolled so that the thickness of the silicone resin becomes, for example, 200 μιη. Thereafter, the silicone resin is irradiated with an electron beam to crosslink and cure the silicone resin, thereby producing silicone rubber. As a result, a laminated film 20 having a soft plastic layer 21 made of silicone rubber is formed. The protective layer 23 is peelable from the soft plastic layer 21. The preferred range of the peel strength is that the protective layer 23 is separated from the soft plastic layer 21 by a T-peel test at a temperature of 20 ° C. with the soft plastic layer 21 fixed at a temperature of 30 Om mZ. When it is peeled off in a direction perpendicular to the soft plastic layer 21, it is 30 to 500 gf / 5 O mm. As the protective layer 23, a biaxially stretched film made of a hard plastic such as polyethylene terephthalate, polypropylene, or polystyrene, a semi-hard plastic such as polyethylene, an ethylene monobutyl acetate copolymer, or a paper surface is used. Those coated with a release agent such as silicone or fluorine are used. Preferably, a biaxially stretched PET film is used from the viewpoint of an appropriate peel strength for the soft plastic layer 21. Subsequently, the laminated film 20 is press-molded, so that it corresponds to a switch. Small convex portions 201 are formed. At this time, since the soft plastic layer 21 is covered with the protective layer 23, the soft plastic layer 21 is not damaged. Next, with the protective layer 23 of the laminated film 20 in contact with the mold surface 40 of the injection mold 4, the laminated film 20 is placed in the injection mold 4, and the opening of the second mold 46 is opened. The part is closed by the first mold 41. Then, the melted acrylonitrile-styrene resin is injected toward the hard plastic layer 22 through the injection hole 411 by an extruder (not shown). The acrylonitrile-styrene resin is injected between the first mold 41 and the hard plastic layer 22 and then cooled. As a result, the acrylonitrile-styrene resin is firmly fused to the hard plastic layer 22 and solidified by cooling to form the injection-molded resin layer 44. As a result, a laminated injection molded article shown in FIG. 5 is obtained.

Finally, the protective layer 23 of the laminated sheet is peeled off, exposing the soft plastic layer 21. A cavity 43 corresponding to the protrusion 42 is formed in the injection molded resin layer 44. For this reason, it is possible to press the small convex portion 201 of the laminated film 20 or to perform display by photoelectric or the like. Further, since the hollow portion 43 is sealed by the hard plastic layer 22 and the injection-molded resin layer 22, water and dust do not enter the hollow portion 43. Therefore, for example, it can be effectively used for a computer keyboard and an operation panel of a home appliance. This embodiment has substantially the same effects as the embodiments shown in FIGS. FIG. 7 shows a film key 50 according to the third embodiment. The film key 50 includes an injection-molded resin layer 52, and a plurality of protrusions 53 are formed on the resin layer 52. On the surface of the injection molded resin layer 52, a laminated film in which a soft plastic layer 21 and a hard plastic layer 22 are firmly bonded is laminated, and the soft plastic layer 21 is disposed on the surface side. Multiple protrusions 5 3 and laminated film covering them Thus, a plurality of button sections 51 are configured. A switch body (not shown) is arranged below each button section 51, and is used, for example, for a key of a mobile phone. Since the back surface of each button portion 51 is reinforced by the injection-molded resin layer 52, no deformation occurs, and the button portion 51 can be formed at a desired height. Therefore, the pressing feeling is firm, and the button portion 51 can be pressed securely. The embodiment is not limited to the above, and may be embodied as follows, for example. The method of crosslinking the silicone rubber is not limited to the method using an electron beam, but may be another method. For example, in order to obtain a silicone elastomer, 150 in an addition type system. Crosslinking takes place at about C. In addition-type systems, a SiH group is added to the carbon double bond by a hydrosilylation reaction to effect crosslinking. As a silicone elastomer, for example, a polysiloxane containing two or more vinyl groups is used as a base polymer, a siloxane oligomer having three or more SiH groups is used as a crosslinking agent, and a platinum compound is used as a catalyst. use. As the protective film, an oriented polypropylene film (OPP) is preferable. However, when using OPP alone, shrinkage occurs during crosslinking, so use PETZOPP laminating film. A protective film is a laminated film in which a biaxially stretched Ρ Ε Τ film is attached to an OP が with a surface matte treatment. Then, similarly to FIG. 1, the soft layer 2 and the silicone rubber composition are cured by heating while being pressed. In this case, an electron beam irradiation device for cross-linking the silicone rubber becomes unnecessary. A laminated film obtained by laminating a commercially available matted OP II with a biaxially stretched PET film may be used as the protective film 4. A laminated sheet having no protective film 4, in other words, a two-layer laminated sheet comprising a hard plastic layer 3 and a soft layer 2 is press-molded to form a membrane switch sheet 12 having a bulged portion 5. Well ,. In this case, no protective film 4 is required As the number of manufacturing steps is reduced, costs are also reduced. A protective film that has not been subjected to a matting process may be used. In this case, the protruding portion is harder to slide and has a better feel when the switch is pressed, as compared with the bulging portion 5 shown in FIG. The silicone rubber layer may be partially cross-linked to the extent that it is difficult for the bulging portion 5 to flow during molding, and may be completely cross-linked after molding. In this case, the effect of reinforcing the flexibility of the hard plastic layer 3 by the silicone rubber layer is improved. As a material of the soft layer 2, for example, urethane rubber may be used. As the hard plastic layer 3, a material other than the PET film, for example, a polyethylene naphthalate film, a polyimide film, a polycarbonate film, or the like may be used. Further, a laminate film of a crystalline polyester film and another film may be used. The arrangement of the bulging portions 5 may be appropriately changed according to the arrangement of the switches of the electric product to be used. The shape of the bulging portion 5 is not limited to a circle, and may be changed to an appropriate shape such as an ellipse, a triangle, and a rectangle. Further, the size of the bulging portion 5 may be appropriately changed according to the design or purpose. The present invention may be applied to a membrane switch having an electrode inside the hard plastic layer 3.

Claims

The scope of the claims

1. a soft layer (2) having two faces,

A first hard plastic layer (3) adhered to one side of the soft layer (2) and a second hard plastic layer (4) releasably attached to the other side of the soft layer (2). ) When

A laminate formed of:

2. The laminated molded body has a bulging portion (5), a soft layer (2) is arranged outside the bulging portion (5), and a first hard plastic is provided inside the bulging portion (5). The laminated molded body according to claim 1, wherein the layer (3) is arranged.

3. a soft layer (2) with two sides,

A hard plastic layer (3) bonded to one side of the soft layer (2) and a hard plastic film (4), the film (4) being a matte-coated surface (4a ), And the matte-coated surface (4a) is pressed against the other surface of the soft layer (2), whereby the film (4) is pressed against the soft layer (2). That they can be peeled off

A laminate formed of:

4. The laminated molded body has a bulging portion (5), a soft layer (2) is disposed outside the bulging portion (5), and a hard plastic layer (3) is provided inside the bulging portion (5). 4. The laminated molded article according to claim 3, wherein

5. The laminated molded article according to claim 3, wherein the soft layer (2) is formed of a crosslinked silicone rubber.

6. The membrane switch sheet (1 2) having the soft layer (2) disposed outside is formed by peeling the film (4) from the laminate formed body. The laminated molded article according to any one of claims 3 to 5.

7. A membrane switch (7) comprising the membrane switch sheet (1 2) according to claim 6.

8. Injection molding resin layer (44),

A laminated film (20) laminated on the injection-molded resin layer (44), wherein the laminated film (20) has a soft plastic layer (21) and a hard plastic layer (22) bonded to each other. ), Wherein the laminated film (20) is laminated on the injection-molded resin layer (44), and the soft plastic layer (21) is disposed on the outside.

9. The laminated molded article according to claim 8, wherein the laminated molded article includes a button portion (51). -

10. A hard plastic layer (2 2) can be bonded to one side of the soft plastic layer (2 1), and a protective layer (2 3) can be peeled off to the other side of the soft plastic layer (2 1). Forming a laminated film (20) by laminating the laminated film (20); and setting the protective layer of the laminated film (20) toward the mold surface (40) of the injection mold (4).

Forming a resin injection layer (44) on the hard plastic layer (22) by injecting a molding material toward the hard plastic layer (22).