Improving adhesion between base material and resilient material layer

Abstract

This invention relates to improving the adhesion between a substrate and an elastic material layer. Plasma-enhanced chemical vapor deposition (PECVD) is performed to deposit a silicon compound layer on a substrate. An elastic material layer is formed on the surface of the silicon compound layer. An object formed by this method may include a substrate, a silicon compound layer on the substrate, and an elastic material layer on the surface of the silicon compound layer. The adhesion between the substrate and the elastic material layer can be significantly improved by using a silicon compound layer with varying surface roughness and thickness.

Description

Technical Field

[0001] This invention relates to a silicone compound layer for improving the adhesion between a base substrate and a resilient material layer. Prior Technology

[0002] Objects having a substrate bonded to an elastic material layer are highly practical and widely used in a variety of applications. This substrate can be formed from glass, metal, plastic, etc. Specifically, objects including substrates bonded to a silicone rubber layer as an elastic material can be used in, for example, household goods, automotive parts, and electronic components such as baby bottles, goggles, and bathroom products, involving heat resistance and / or transparency and chemical safety.

[0003] Typically, elastic materials are bonded to a substrate by enhancing the adhesive properties of the silicone rubber layer, applying a primer to the surface of the base substrate, and using an adhesive to attach the hardened silicone rubber and the substrate material. However, enhancing the adhesive properties of the silicone rubber layer is usually achieved by adding highly reactive materials (e.g., carbon functional silanes), which can lead to poor heat resistance and easy deformation of the material. Furthermore, during injection molding, reactive materials can also adhere to the mold itself, making it difficult to control the quality of the molding process.

[0004] Furthermore, applying a primer to the substrate surface involves a complex process of application, drying, and baking, and defects can arise due to uneven primer application. While other methods exist to improve substrate adhesion (e.g., UV irradiation, plasma treatment, and corona treatment), these methods do not adequately enhance adhesion to the base material and typically require hazardous working environments and expensive equipment. Additionally, attaching silicone rubber layers to the substrate using adhesives can be challenging because adhesives often have poor heat resistance or durability and may be damaged during manufacturing. Summary of the Invention

[0005] The embodiments relate to an article of manufacture comprising a substrate, a silicon compound layer on the substrate, and an elastic material layer on the surface of the silicon compound layer. The silicon compound layer has a surface roughness in Ra between 50 nm and 600 nm.

[0006] In one or more embodiments, the thickness of the silicon compound layer described above is less than 1000 nm but greater than 50 nm.

[0007] In one or more embodiments, the silicon compound layer described above is a SiOxCyHz layer.

[0008] In one or more embodiments, the SiO xC yH z layer described above comprises 28-30% silicon by weight, 60-65% oxygen by weight, 0-1% carbon by weight, and 6-9% hydrogen by weight.

[0009] In one or more embodiments, the substrate described above includes at least one of thermoplastic polymer, thermosetting polymer, silicone rubber, metal, and glass.

[0010] In one or more embodiments, the thermoplastic polymer described above is at least one of polypropylene (PP), polyester (PES), polystyrene (PPSU), polyamide (PA), tritan, polycarbonate (PC), and nylon.

[0011] In one or more embodiments, the elastic material layer described above is a material selected from liquid silicone rubber (LSR), thermosetting silicone rubber (HCR), and combinations thereof.

[0012] In one or more embodiments, the substrate is PPSU and the elastic material layer is silicone rubber.

[0013] In one or more embodiments, the aforementioned silicon compound layer system is deposited on a substrate using plasma-enhanced chemical vapor deposition (PECVD).

[0014] In one or more embodiments, the plasma-enhanced chemical vapor deposition (PECVD) described above is performed by reacting the precursor hexamethyldisiloxane (HMDSO) with the reactive gas oxygen (O2) under plasma conditions.

[0015] The embodiments also relate to a method of manufacturing an article of manufacture. Plasma-enhanced chemical vapor deposition (PECVD) is performed to deposit a silicon compound layer on a substrate of the article. An elastic material layer is formed on the surface of the silicon compound layer.

[0016] In one or more embodiments, the thickness of the silicon compound layer described above is less than 1000 nm but greater than 50 nm.

[0017] In one or more embodiments, the silicon compound layer described above has a surface roughness in Ra units between 50 nm and 600 nm.

[0018] In one or more embodiments, the silicon compound layer described above is a SiOxCyHz layer.

[0019] In one or more embodiments, the SiO xC yH z layer described above comprises 28-30% silicon by weight, 60-65% oxygen by weight, 0-1% carbon by weight, and 6-9% hydrogen by weight.

[0020] In one or more embodiments, the substrate described above includes at least one of thermoplastic polymer, thermosetting polymer, silicone rubber, metal, and glass.

[0021] In one or more embodiments, the thermoplastic polymer described above is at least one of polypropylene (PP), polyester (PES), polystyrene (PPSU), polyamide (PA), tritan, polycarbonate (PC), and nylon.

[0022] In one or more embodiments, the elastic material layer described above is a material selected from liquid silicone rubber (LSR), thermosetting silicone rubber (HCR), and combinations thereof.

[0023] In one or more embodiments, the substrate is polystyrene (PPSU) and the elastic material layer is silicone rubber.

[0024] In one or more embodiments, the plasma-enhanced chemical vapor deposition (PECVD) described above is performed by reacting the precursor hexamethyldisiloxane (HMDSO) with the reactive gas oxygen (O2) under plasma conditions.

[0025] In one or more embodiments, forming the elastic material layer includes injecting an elastic material in liquid form into a mold on which a substrate on which the elastic material layer is deposited is placed. Simple Explanation of the Diagram

[0026] [Figure 1] shows a flowchart of a method for bonding an elastic material layer to a substrate according to one embodiment.

[0027] [Figure 2] shows the structure of a substrate, a silicon compound layer, and an elastic material layer according to one embodiment.

[0028] [Figure 3] shows a cross-sectional view of a surface of a polymer material substrate on which no silicon compound layer has been deposited, according to a comparative example.

[0029] [Figures 4A-4C] show cross-sectional views taken through the surface of a polymer material substrate according to some embodiments, each substrate having a silicon compound layer with a thickness below a threshold level and a roughness below a threshold level.

[0030] [Figures 5A-5C] show cross-sectional views taken through the surface of a polymer material substrate according to some embodiments, each substrate having a silicon compound layer with a thickness below a threshold and a roughness within the threshold range.

[0031] [Figure 6] shows a cross-sectional view taken across the surface of a polymer material substrate having a silicon compound layer with a thickness above a threshold and a roughness within a threshold range, according to one embodiment.

[0032] [Figure 7] shows a cross-sectional view taken across the surface of a polymer material substrate having a silicon compound layer with a thickness below a threshold and a roughness above a threshold range, according to one embodiment. Implementation

[0033] Hereinafter, embodiments of the present invention are described with reference to the accompanying drawings. However, the principles disclosed in the present invention can be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Details of known features and techniques may be omitted in the description to avoid unnecessarily obscuring the characteristics of the embodiments. In the drawings, the same reference numerals denote the same elements. For clarity, the shapes, sizes, and areas of the drawings may be enlarged.

[0034] Embodiments of the present invention relate to articles of manufacture having a substrate bonded to an elastic material layer, and methods for manufacturing such articles. A silicon compound layer having a predetermined surface roughness is deposited on a base substrate, and an elastic material layer is formed on the silicon compound layer to enhance the adhesion between the substrate and the elastic material layer. The aforementioned silicon compound layer can be deposited using a plasma-enhanced chemical vapor deposition (PECVD) method, with an average thickness of less than 1000 nm and a surface roughness of 50 nm to 600 nm in Ra units. Such articles can be used as high-heat-resistant components (e.g., automotive parts and electronic components) or transparent and chemically safe components (e.g., baby bottles, goggles, and bathroom products). [Methods for bonding elastic material layers to a substrate]

[0035] Figure 1 shows a flowchart of a method for bonding an elastic material layer to a substrate according to one embodiment. The following embodiments use a silicone rubber layer as an example of the elastic material layer, but are not limited to this; different materials can be used for the elastic material layer.

[0036] First, a substrate is prepared for the object (step 102). The substrate can be formed from one of the following materials: thermoplastic polymer, thermosetting polymer, silicone rubber, metal, such as stainless steel, aluminum, gold, silver, copper, iron, or inorganic materials, such as alumina, titanium dioxide, and glass. In particular, when the substrate includes a thermoplastic polymer, it can be formed from polypropylene (PP), polyester resin (PES), polystyrene resin (PPSU), polyamide (PA), tritan, polycarbonate (PC), and nylon. These thermoplastic polymers have high heat resistance and impact resistance. Therefore, substrates containing thermoplastic polymers are advantageous for use in medical devices, baby products, kitchen products, and similar applications requiring repeated sterilization in high temperature and humidity.

[0037] Then, a deposition method is performed to deposit a silicon compound layer on the substrate (step 104). The silicon compound layer may be a SiOxCyHz layer primarily composed of silicon dioxide. Specifically, the SiOxCyHz layer has an average thickness of less than 1000 nm and a surface roughness ranging from 50 nm to 600 nm in Ra units. Ra represents the arithmetic mean of the absolute values ​​of the profile height deviations from the midline of the layer surface. The range of surface roughness and thickness of SiOxCyHz for the effectiveness of silicone adhesion to the substrate is determined based on experiments described in detail below with reference to Figures 3 to 7.

[0038] The surface roughness of silicon compound layers (e.g., SiO₂xC₂yH₂ layers) can be measured using atomic force microscopy (AFM), as described in the paper "Profile Surface Roughness Measurement Using Metrological Atomic Force Microscopy and Uncertainty Evaluation" presented by Ichiko Misuzu et al. at the 11th Laser Metrology for Precision Measurement and Inspection in Industry 2014 (September 2-5, 2014), the entire contents of which are incorporated herein by reference. The surface roughness of the examples described below with reference to Figures 3 through 7 was measured using the same method.

[0039] The thickness of the silicon compound layer (e.g., SiO₂xC₂yH₂ layer) can be determined by analyzing images obtained using a scanning electron microscope (SEM). First, the substrate surface, with or without the silicon compound, is pretreated with a platinum coating to prevent any damage to the silicon compound layer. Then, the pretreated surface is treated with a focused ion beam (FIB). A cross-section of the FIB-treated surface is then captured using SEM. The pixels of the captured image are then analyzed to determine the thickness at multiple points in the image. The average thickness obtained from these multiple points is taken as the thickness of the silicon compound layer.

[0040] In one embodiment, the silicon compound layer with surface roughness is achieved by depositing the silicon compound layer through plasma-enhanced chemical deposition (PECVD). In one case, the PECVD process can be performed under relatively low temperature and low pressure conditions to obtain the desired surface roughness of the silicon compound layer on the substrate. The pressure of the PECVD process can be from 1 × 10⁻² to 1 Torr, and the temperature of the substrate can be from 50°C to 200°C during at least part or all of the PECVD process. A silicon-containing precursor gas and a reactive gas can be used in the above-described PECVD process. The silicon-containing precursor is hexamethyldisiloxane (HMDSO), and the reactive gas is oxygen (O₂).

[0041] The silicon compound layer formed by this PECVD process can be a SiO₂xC₂yH₂ layer. In one or more embodiments, the proportions of silicon, oxygen, carbon, and hydrogen are in the ranges of 28-30 wt%, 60-65 wt%, 0-1 wt%, and 6-9 wt%, respectively, where wt% represents weight percentage. The composition of the silicon compound layer can be determined using, for example, Rutherford Backscattering Spectroscopy (RBS)-Elastic Recoil Detection (ERD), a method well-known in the art.

[0042] Referring again to Figure 1, an elastic material layer is formed on the surface of the silicone compound layer (step 106). Specifically, the elastic material layer can be formed by coating an elastic material onto the surface of a silicone compound layer having a surface roughness within a threshold range. Its function is to improve the adhesion between the substrate and the resulting elastic material layer. The elastic material can be liquid silicone rubber (LSR), thermosetting rubber (HCR), or a combination thereof.

[0043] In one embodiment, an elastic material is applied to the substrate having a silicone compound layer by placing or fixing an object comprising a substrate and a silicone compound layer in a mold of an injection molding machine (injection molding machine) and filling the mold. The elastic material is applied to the surface of the silicone compound layer by the injection molding machine.

[0044] In one embodiment, the surface of the substrate is plasma-treated before depositing the silicon compound layer. Plasma treatment reduces contaminants or other particles on the substrate and can lead to improved adhesion between the substrate and the deposited silicon compound layer.

[0045] Furthermore, an ionization process can be performed on the surface of the silicone compound layer before forming the elastic material layer. Although the relatively high surface roughness of the silicone compound layer improves the physical and mechanical adhesion to the elastic material layer, performing the ionization process can further improve the adhesion by increasing the surface energy of the silicone compound layer. [Composite Structure]

[0046] Figure 2 shows a composite structure 100 according to one embodiment, including a substrate 110, a silicon compound layer 130, and an elastic material layer 120. This composite structure 100 can form part or all of an article and can be obtained by performing the steps described in detail in conjunction with Figure 1.

[0047] The substrate 110 is formed as the base material of the composite structure 100 and can be formed by the materials and properties described in conjunction with step 102 of the method shown in FIG. 1. The elastic material layer 120 provides texture and impact resistance to the object formed by the composite structure 100 and can be formed by step 106 of forming the elastic material layer in conjunction with the materials and properties described above in FIG. 1.

[0048] A silicon compound layer 130 is formed between the substrate 110 and the elastic material layer 120, and is formed using the materials and properties described in conjunction with step 104 of the method shown in FIG. 1. Specifically, the surface of the silicon compound layer 130 at the interface with the elastic material layer 120 may have a surface roughness within a threshold range to improve the bonding between the elastic material layer 120 and the substrate 110. The silicon compound layer 130 may also have an average thickness below a threshold. In one embodiment, the substrate 110 may be formed of PPSU, the elastic material layer 120 may be formed of silicone rubber, and the silicon compound layer 130 may have a surface roughness of 50 nm to 600 nm and an average thickness of less than 1000 nm but more than 50 nm. [Experimental Results]

[0049] In the following example, the adhesion of silicone to a baby bottle container made of PPSU with a SiO₂xC₂yH₂ layer was tested. In this example, an ionization process was performed to activate the surface of the PPSU, and then a SiO₂xC₂yH₂ layer was formed using a PECVD process involving HMDSO as a Si-containing precursor and O₂ as a reactive gas. The PPSU substrate in the form of a baby bottle with the SiO₂xC₂yH₂ layer was then placed in a mold of an injection molding machine, and LSR silicone was filled into the mold. The PPSU substrate with the LSR silicone was then cooled to cure the silicone. After the silicone was adhered to the PPSU through the SiO₂xC₂yH₂ layer, the baby bottle was immersed in boiling water at 2 atmospheres for a predetermined time to determine whether the adhesion between the PPSU and the silicone was maintained. No separate adhesive was placed between the SiO xC yH z layer and the silicone to bond the silicone to the PPSU substrate.

[0050] Figure 3 is a scanning electron microscope (SEM) image of a cross-sectional view taken across the surfaces of the PPSU substrate and silicone, according to a comparative example, without any SiOxCyHz layer deposited. Therefore, the thickness of the SiOxCyHz layer is zero, and the roughness of the PPSU substrate is less than 5 nm (Ra). Without the SiOxCyHz layer, the silicone separates from the PPSU even before immersion in boiling water.

[0051] Figures 4A to 4C are SEM images of cross-sectional views taken across the surface of a PPSU substrate with a SiO xC yH z layer having a roughness level below a threshold, according to some embodiments. That is, the roughness of the SiO xC yH z layer is less than 50 nm (Ra). Figure 4A is an SEM image of the PPSU substrate where the average thickness of the SiO xC yH z layer is 42.8 nm and the roughness of the SiO xC yH z layer is 0.26 nm (Ra). Figure 4B is an SEM image of the PPSU substrate where the thickness of the SiO xC yH z layer is 197 nm and the roughness of the SiO xC yH z layer is 11.15 nm (Ra). In this example, three separate PECVD cycles are performed to obtain the final thickness of the SiO xC yH z layer. Figure 4C is an SEM image of the PPSU substrate where the thickness of the SiO xC yH z layer is 721 nm and the roughness of the SiO xC yH z layer is 25.64 nm (Ra). In the examples shown in Figures 4A to 4C, the silicone initially adhered to the PPSU substrate, but separated after the substrate and silicone were immersed in boiling water for 30 hours. Therefore, these examples demonstrate that if the roughness of the SiO₂xC₂yH₂ layer is less than 50 nm (Ra), the silicone cannot adequately adhere to the substrate even if the thickness of the SiO₂xC₂yH₂ layer is less than 1000 nm.

[0052] Figures 5A to 5C are SEM images of cross-sectional views taken across the surface of a PPSU substrate with a SiO xC yH z layer having a roughness within a predetermined range, according to some embodiments. That is, the roughness of the SiO xC yH z layer is 50 nm (Ra) or more and less than 600 nm (Ra). Figure 5A is an SEM image of a PPSU substrate, wherein the average thickness of the SiO xC yH z layer is 127.3 nm and the roughness of the SiO xC yH z layer is 56.85 nm (Ra). Figure 5B is an SEM image of a PPSU substrate, wherein the average thickness of the SiO xC yH z layer is 263.1 nm and the roughness of the SiO xC yH z layer is 203.4 nm (Ra). Figure 5C is an SEM image of a PPSU substrate, wherein the average thickness of the SiO xC yH z layer is 400.7 nm and the roughness of the SiO xC yH z layer is 454 nm (Ra). As shown in the examples in Figures 5A to 5C, the silicone adheres to the PPSU substrate and remains adhered even after the substrate and silicone have been immersed in boiling water for 50 hours. Therefore, these examples demonstrate that if the roughness of the SiO xC yH z layer is within the threshold range of 50 nm (Ra) to 600 nm (Ra) and the average thickness of the SiO xC yH z layer is less than 1000 nanometers.

[0053] Figure 6 is a SEM image of a cross-sectional view taken across the surface of a PPSU substrate according to some embodiments, where the roughness of the SiO xC yH z layer is within a threshold range, but the average thickness of the SiO xC yH z layer is above the threshold level. Specifically, the average thickness of the SiO xC yH z layer is 1,207.9 nm, and the roughness of the SiO xC yH z layer is 224.1 nm (Ra). In this example, the silicone initially adhered to the PPSU substrate but separated from the substrate after immersion in boiling water for 30 hours. This example demonstrates that if the thickness of the SiO xC yH z layer is greater than 1000 nm, the silicone cannot adequately adhere to the substrate.

[0054] Figure 7 is a cross-sectional view of the surface of a PPSU substrate with a silicone compound layer having a thickness below a threshold level and a roughness above a threshold range, according to one embodiment. In the example shown in Figure 7, the SiO xC yH z layer has a thickness of 256.6 nm and a roughness of 732 nm (Ra). In this example, the silicone initially adhered to the PPSU substrate but separated from it after immersion in boiling water for 30 hours. This example demonstrates that if the roughness of the SiO xC yH z layer exceeds 600 nm (Ra), the silicone cannot adequately adhere to the substrate even if the thickness of the SiO xC yH z layer is less than 1000 nm.

[0055] In addition to the experiments described above, experiments were also conducted using materials other than PPSU as substrates. Specifically, lap-shear tests were performed according to ASTM D1002 using two specimens, each with a silicone compound layer deposited (e.g., a SiO₂xC₂yH₂ layer). LSR was then coated onto the surface of one specimen with the silicone compound layer deposited. Another specimen was then overlapped with the surface having the silicone compound layer deposited facing the LSR-coated surface. The specimen was pressed to achieve a predetermined LSR thickness (e.g., 1 mm) and then baked to cure the LSR into silicone. The two specimens were then pulled in opposite directions to test the failure shear of the overlapping portion.

[0056] The suitability of silicon compounds for these materials was tested by measuring the maximum shear force before failure of different materials (e.g., polycarbonate, glass, polypropylene, and stainless steel) as test samples. The SiOxCyHz layers were deposited under PECVD conditions similar to those in Figures 5A to 5C. Therefore, it was assumed that the thickness of the materials in Figures 5A to 5C was less than 1000 nm and the roughness was in the range of 50 nm (Ra) to 600 nm (Ra). Three lap-shear tests were performed on each material with and without the SiOxCyHz layer, and the average maximum shear force was compared. The results are as follows: [Table 1] Sample materials Maximum shear force (without SiO₂ xC yH z layers) (Unit: Newton) Maximum shear force (with SiO₂ xC₂yH₂ layers) (Unit: Newton) Polycarbonate 91.7 N 1620.7 N Glass 209.3 N 410 N Polypropylene 136.7 N 967 N Stainless steel (SUS304) 4N 2765.3 N

[0057] As shown in Table 1, the maximum shear force increases significantly when a SiOxCyHz layer is deposited on the sample material. In the case of stainless steel, the increase in shear force due to the deposition of the SiOxCyHz layer is approximately 691 times. Although only PPSU, polycarbonate, glass, polypropylene, and stainless steel were used as substrate materials, similar results are expected in other materials.

[0058] The above description is a preferred embodiment of the present invention. Those skilled in the art should understand that it is used to illustrate the present invention and not to limit the scope of the patent rights claimed by the present invention. The scope of patent protection shall be determined by the appended claims and their equivalent fields. Any modifications or refinements made by those skilled in the art without departing from the spirit or scope of this patent are equivalent changes or designs made under the spirit disclosed in the present invention and should be included in the scope of the following claims.

[0059] 102, 104, 106: Steps 100: Composite structure 110:Substrate 120: Elastic material layer 130: Silicon compound layer

Claims

1. A structure for improving adhesion between a substrate and an elastic material layer, comprising: One substrate; A silicon compound layer is formed on the substrate, the silicon compound layer having an outer surface and the surface roughness of the outer surface, in Ra units, being between 50 nm and 600 nm; a silicone rubber layer is directly located on the outer surface of the silicon compound layer; wherein the substrate comprises at least one of a thermoplastic polymer, a thermosetting polymer, silicone rubber, a metal, and glass; wherein the thermoplastic polymer comprises at least one of polypropylene (PP), polyester styrene (PES), polystyrene styrene (PPSU), polyamide (PA), tritan, polycarbonate (PC), and nylon; and wherein the thickness of the silicon compound layer is less than 1000 nm but greater than 50 nm; wherein the silicon compound layer comprises silicon, oxygen, carbon, and hydrogen.

2. The structure for improving adhesion between the substrate and the elastic material layer as described in claim 1, wherein the silicon compound layer comprises 28-30% by weight silicon, 60-65% by weight oxygen, and 6-9% by weight hydrogen.

3. The structure for improving adhesion between the substrate and the elastic material layer as described in claim 1, wherein the substrate is polystyrene (PPSU).

4. The structure for improving adhesion between the substrate and the elastic material layer as described in claim 1, wherein the silicon compound layer is deposited on the substrate using plasma-enhanced chemical vapor deposition (PECVD).

5. The structure for improving adhesion between the substrate and the elastic material layer as described in claim 4, wherein the plasma-enhanced chemical vapor deposition (PECVD) is performed by reacting the precursor hexamethyldisiloxane (HMDSO) with the reactive gas oxygen (O2) under plasma.

6. A method for improving the adhesion between a substrate and an elastic material layer, comprising: Performing plasma-enhanced chemical vapor deposition (PECVD) to deposit a silicon compound layer on a substrate of an article, the outer surface of the silicon compound layer having a surface roughness in Ra units between 50 nm and 600 nm; forming a silicone rubber layer on one surface of the silicon compound layer; wherein the substrate comprises at least one of a thermoplastic polymer, a thermosetting polymer, silicone rubber, a metal, and glass; wherein the thermoplastic polymer comprises at least one of polypropylene (PP), polyester resin (PES), polystyrene resin (PPSU), polyamide (PA), tritan, polycarbonate (PC), and nylon; and wherein the thickness of the silicon compound layer is less than 1000 nm but greater than 50 nm; wherein the silicon compound layer comprises silicon, oxygen, carbon, and hydrogen.

7. The method for improving adhesion between a substrate and an elastic material layer as described in claim 6, wherein the silicon compound layer comprises 28-30% by weight silicon, 60-65% by weight oxygen, and 6-9% by weight hydrogen.

8. The method for improving the adhesion between a substrate and an elastic material layer as described in claim 6, wherein the substrate is polystyrene (PPSU).

9. The method for improving adhesion between a substrate and an elastic material layer as described in claim 6, wherein the plasma-enhanced chemical vapor deposition (PECVD) is performed by reacting the precursor hexamethyldisiloxane (HMDSO) with the reactive gas oxygen (O2) under plasma conditions.

10. The method for improving adhesion between a substrate and an elastic material layer as described in claim 6, wherein forming the silicone rubber layer comprises injecting silicone rubber in liquid form into a mold and applying the silicone rubber to the substrate having the silicone compound layer, wherein an injection molding machine having the silicone rubber coats the silicone rubber onto the surface of the silicone compound layer.

Images