Protective film assembly for electronic device and method of manufacturing the same

Abstract

The application provides a protective film assembly of an electronic device and a preparation method thereof. The protective film assembly comprises a pull-tab type protective film, and the pull-tab type protective film comprises: a protective film glass, a glue layer arranged on the back of the protective film glass, and a pull-tab layer arranged on the side of the glue layer away from the protective film glass. The warping degree of the protective film glass is greater than or equal to 0.8 mm, and the back is concave. The protective film assembly and the preparation method provided by the application can improve the exhaust effect of the pull-tab type protective film when applied to the electronic device.

Description

Technical Field

[0001] This invention relates to the field of screen protector technology, and more particularly to a screen protector assembly for electronic devices and its preparation method. Background Technology

[0002] During tablet use, users typically apply screen protectors to protect the screen from scratches during daily use. Compared to traditional screen protectors, pull-out screen protectors greatly simplify the application process. Simply align the protector with the screen and pull out the strip; the protector will automatically adhere to the screen as the strip is pulled out, automatically expelling air bubbles in the process. However, existing pull-out screen protectors are primarily designed for mobile phones. When used on tablets, they often suffer from poor automatic air expulsion, leading to a high probability of trapped air bubbles and a lower application success rate.

[0003] Therefore, improving the automatic air venting effect when applying a strip-type protective film to a tablet computer has become a problem to be solved. Summary of the Invention

[0004] Therefore, in order to overcome at least some of the defects and deficiencies in the prior art, embodiments of the present invention provide a protective film assembly for electronic devices and a method for preparing the same, which can improve the air venting effect of the strip-type protective film in tablet computer screen protector application.

[0005] Specifically, in one aspect, embodiments of the present invention provide a protective film assembly for an electronic device, the protective film assembly including a pull-tab type protective film, the pull-tab type protective film including: a protective film glass, an adhesive layer disposed on the reverse side of the protective film glass; and a pull-tab layer disposed on the side of the adhesive layer away from the protective film glass; the warpage of the protective film glass is greater than or equal to 0.8 mm and the reverse side is concave.

[0006] In some embodiments, the reverse side of the protective film glass is gradually concave from both ends toward the middle along its length.

[0007] In some embodiments, the warpage of the protective film glass is less than or equal to 1.5 mm.

[0008] In some embodiments, the protective film assembly further includes an applicator; the front side of the protective film glass is also provided with an upper protective layer, the edge of the upper protective layer extending out of the protective film glass and fixedly connected to the applicator; the upper protective layer includes a substrate and an adhesive disposed on the surface of the substrate, the adhesive being bonded to the front side of the protective film glass, and the adhesive having a tack of 5~8g.

[0009] In some embodiments, the thickness of the upper protective layer is 0.125~0.145 mm.

[0010] This invention also provides a preparation method for a protective film assembly of an electronic device as described in any of the foregoing embodiments; the preparation method includes a glass processing step, the glass processing step specifically including: (1) Cut the glass and perform CNC edge grinding; (2) After CNC edge grinding, perform the first polishing treatment on the front of the glass; (3) Tempering is performed after the first polishing process; (4) After tempering, the front of the glass is polished a second time.

[0011] In some embodiments, the tempering temperature is 380°C to 410°C, and the tempering time is 2 to 3 hours.

[0012] In some embodiments, the tempering temperature is 410°C and the tempering time is 2 hours; or the tempering temperature is 380°C and the tempering time is 3 hours.

[0013] In some embodiments, the pressure applied to the front surface of the glass during the second polishing process is 2~4 kg / cm². 2 The duration is 10-15 seconds.

[0014] In some embodiments, the glass is float glass, the front side is the air side of the float glass, and the back side is the tin side of the float glass.

[0015] The embodiments of the present invention have at least the following beneficial effects: By controlling the warpage of the protective film glass to be greater than or equal to 0.8mm, the distance between the middle part of the protective film glass and the screen is slightly greater than the distance between the two ends of the screen during film application. This reduces the problem of air bubbles being unable to escape between the middle and end areas due to the middle area of ​​the protective film glass adhering to the screen first during the application process. This ensures that air is released from the top to the bottom of the screen, reducing the probability of air bubbles trapped, improving the air release effect during film application, and increasing the success rate of film application. At the same time, since the protective film glass has a large area, it will deform under the action of gravity during the application process. Controlling the warpage to be greater than or equal to 0.8mm can offset the deformation of the protective film glass during the application process, thereby further improving the air release effect during the application process. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of the protective film glass in the protective film assembly provided in the embodiments of this application.

[0018] Figure 2 This is a schematic diagram of the overall structure of the protective film assembly provided in the embodiments of this application during the application of the protective film.

[0019] Figure 3 for Figure 2 A schematic diagram of its decomposed structure.

[0020] Figure 4 This is a diagram illustrating the bubble trapping effect during film application.

[0021] Figure 5 This is a schematic flowchart of the glass processing steps in the method for preparing the protective film assembly of the electronic device provided in the embodiments of this application. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments described in the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0023] This invention provides a protective film assembly for an electronic device. In this embodiment, the electronic device is, for example, a tablet computer, e-reader, or other electronic device with a screen size of 8 inches or larger, and its screen is a flat screen. Specifically, the screen size is from 8 inches to 13 inches; for example, commercially available iPads have screen sizes of 8.3 inches, 10.2 inches, 10.9 inches, 11 inches, and 13 inches.

[0024] The protective film assembly provided in this embodiment of the invention includes a strip-type protective film 10, as shown in the reference. Figure 2 and Figure 3 The pull-tab protective film 10 includes: a protective film glass 11, an adhesive layer 12 disposed on the reverse side 112 of the protective film glass 11, and a pull-tab layer 13 disposed on the side of the adhesive layer 12 away from the protective film glass 11. The warpage of the protective film glass 11 is greater than or equal to 0.8 mm, and the reverse side 112 is concave. (Refer to...) Figure 1 As shown, the front side 111 of the protective film glass 11 is convex, and the back side 112 is concave. Figure 1The left-right direction is the length direction of the protective film glass 11. The reverse side 112 of the protective film glass 11 is concave from both ends to the middle along its length direction. That is, when the reverse side of the protective film glass 11 is placed facing a placement plane, the distance between the reverse side 112 and the placement plane gradually increases from both ends to the middle along the length direction of the protective film glass 11.

[0025] The protective film glass 11 can be made of materials such as high-aluminosilicate glass or lithium-aluminosilicate glass. It can also be classified as float glass based on the glass manufacturing process. The thickness of the protective film glass 11 is, for example, 0.15~0.8mm, specifically 0.33mm. The adhesive layer 12 is used to bond the protective film glass 11 to the screen, specifically, for example, AB glue. The pull strip layer 13 includes a release film portion 131 and a pull strip portion 132. The release film portion 131 covers the adhesive layer 12, and the pull strip portion 132 includes a free end 1321 and a fixed end 1322, with the fixed end 1322 fixedly connected to one end of the release film portion 131. When applying the film, the pull strip layer 13 of the pull strip protective film 10 faces the screen. The user pulls the free end 1321 of the pull strip portion 132 to separate the release film portion 131 from the adhesive layer 12, allowing the screen and the protective film glass 11 to be bonded together through the adhesive layer 12.

[0026] In some embodiments, refer to Figure 2 and Figure 3 The protective film assembly also includes an applicator 20. The applicator 20 is used to align the electronic device 30 with the pull-tab protective film 10. The applicator 20 includes, for example, a base 21 with a device positioning groove formed therein, allowing the electronic device 30 to be placed in the device positioning groove and the pull-tab protective film 10 to be fixed to the applicator 20 to achieve alignment between the pull-tab protective film 10 and the screen. The applicator 20 also includes, for example, a top cover 22, which is connected to one end of the base 21, and specifically, the top cover 22 can be flipped relative to the base 21. The top cover may also have a pressing element 23, which may be made of foam, for example.

[0027] The pull-tab protective film 10 also includes an upper protective layer 14 covering the front surface 111 of the protective film glass 11. The upper protective layer 14 is made of, for example, acrylic. The edge of the upper protective layer 14 extends beyond the protective film glass 11 and is fixedly connected to the applicator 20. The protective film glass 11 has a top end and a bottom end opposite each other along its length. Specifically, the upper protective layer 14 is provided with a first positioning part corresponding to the top end of the protective film glass 11, and the applicator 20 is provided with a second positioning part. When applying the film, the first positioning part and the second positioning part can be connected to position the protective film glass 10 and the applicator 20 through the upper protective layer 14. The first positioning part is, for example, a portion of the upper protective layer 14 extending beyond the top end of the protective film glass 11, and is provided with a positioning hole thereon. The second positioning part is, for example, a positioning post or a hanging ear, etc.

[0028] The protective film assembly is used as follows: Place the electronic device to be covered in the device positioning slot with the screen facing the top cover. Connect the pull strip protective film 10 to the applicator 20 through the first positioning part and the second positioning part on the upper protective layer 14. Flip the top cover 22 onto the upper protective layer 14 so that the pressure member 23 presses the top of the protective film glass 10. Pull the free end 1321 of the pull strip part 132 toward the bottom of the protective film glass 11 to separate the release film part 131 from the adhesive layer 12. The top of the protective film glass 11 is squeezed by the pressure member 23 and adheres to the screen from the top to the bottom.

[0029] In conventional thinking, the protective glass of electronic device screen protectors is usually matched to the screen type. For example, for curved screens, 3D hot-bent glass is chosen. For flat screens, the protective glass is also flat glass, and warping needs to be avoided to prevent poor airflow. However, the inventors discovered during production practice that when applying the strip-type screen protector to electronic devices with larger screens such as tablets, the larger size of the protector causes the middle part of the glass to sag during application, adhering to the screen first and creating a "competition for airflow" problem, resulting in issues such as... Figure 4 The air bubbles in the area between the middle and the top shown cannot be expelled, resulting in trapped air bubbles.

[0030] This application breaks away from the conventional thinking that "the flatter the protective film, the better the air venting effect." By setting the protective film glass to a concave shape on the reverse side, the distance between the center of the protective film glass and the screen surface is greater than the distance between the ends and the screen surface before application. This alleviates the problem of the center of the protective film glass contacting the screen first during application, ensuring air venting from the top to the bottom of the screen. Experiments have shown that when the warpage of the protective film glass is controlled to be greater than or equal to 0.8mm, it has a better air venting effect, alleviating the aforementioned bubble problem and greatly improving the success rate of application. In some embodiments, to avoid excessive warpage of the protective film glass causing glass distortion and affecting the final application effect, the warpage of the protective film glass is controlled to be less than or equal to 1.5mm.

[0031] In some embodiments, the specific upper protective layer 14 includes a substrate and an adhesive disposed on the surface of the substrate. The adhesive is adhered to the front side 111 of the protective film glass 11. The adhesive has a viscosity of 5-8g, and the substrate is, for example, acrylic material. The viscosity of the upper protective layer adhesive can be tested using a peel force tester. To further avoid the problem of bubble formation caused by the middle of the protective film glass 11 adhering to the screen first, this embodiment controls the viscosity of the upper protective layer 14 adhesive so that the upper protective layer can provide a certain pulling force to the protective film glass 11 to prevent the middle of the protective film glass 11 from collapsing first. It also avoids that the viscosity is too high, which would prevent the protective film glass 11 from adhering well to the screen, causing the tail to not be able to expel air and ultimately affecting the film application effect.

[0032] In some embodiments, the thickness of the upper protective layer 14 is 0.125~0.145mm. The design of the thickness of the upper protective layer 14 balances its flexibility and support. Ensuring its support allows the upper protective layer 14 to provide high tensile strength to the protective film glass 11, preventing the center of the protective film glass 11 from collapsing first. Ensuring its flexibility prevents problems with exhaust at the tail end. This avoids increasing the overall cost of the protective film assembly due to an excessively thick upper protective layer 14.

[0033] One embodiment of the present invention also provides a method for preparing a protective film assembly for the above-mentioned electronic device. The method includes a glass processing step, wherein the glass processing step is used to process the glass to obtain a protective film glass with a warpage greater than or equal to 0.8 mm. (Refer to...) Figure 5 The glass processing steps specifically include: (1) Cut the glass and perform CNC edge grinding; (2) After CNC edge grinding, perform the first polishing treatment on the front of the glass; (3) Tempering is performed after the first polishing process; (4) After tempering, the front of the glass is polished a second time.

[0034] Cutting refers to the process of cutting large sheets of glass into multiple smaller pieces of glass of appropriate size according to the required dimensions.

[0035] CNC (Computer Numerical Control) edge polishing is used to round the edges of the sliced ​​glass. In this embodiment, CNC edge polishing is performed twice. The first time, for example, a 400-grit grinding head is used for initial shaping, and the second time, a 900-1200-grit grinding head is used for fine finishing. Alternatively, different parts of the same grinding head along its length can be used for different precision during the two CNC edge polishing processes. After CNC edge polishing, micro-cracks may appear at the edges of the glass surface. The second fine finishing process can make these micro-cracks even finer. A 1200-grit grinding head is preferably used for the second polishing.

[0036] The first polishing process thins the glass by 2-3 micrometers, which can repair minor scratches on the glass surface. The polishing time for this first process is 150-200 seconds, and the pressure applied to the glass surface is 2-4 kg / cm². 2 The specific gravity of the polishing slurry is 1.06~1.1, which means the density of the polishing slurry is 1.06~1.1 g / cm³. 3 The grinding slurry model is JX1201 / JJH-1180 (0.8~1.4) μm, and the rotation speed is 600~900 RPM (RPM is an abbreviation for Revolutions Per Minute).

[0037] The tempering process specifically includes preheating the glass in a preheating furnace, and then immersing the glass in tempering salt for ion exchange. The temperature difference between the ion exchange and the preheating temperature is less than or equal to 30°C. The tempering salt is potassium nitrate with a concentration of 99.9% or higher.

[0038] The pressure applied to the glass surface during the second polishing process is 2~4 kg / cm². 2 The specific gravity of the polishing slurry is 1.06~1.1, which means the density of the polishing slurry is 1.06~1.1 g / cm³. 3 The grinding slurry model is JX1201 / JJH-1180 (0.8~1.4) μm, and the rotation speed is 600~900 RPM (RPM is an abbreviation for Revolutions Per Minute).

[0039] After the second polishing process, step (5) is also included: electroplating AF (Anti-Fingerprint) treatment. Specifically, the electroplating AF treatment uses Shin-Etsu's ultra-smooth electroplating pellets with a coefficient of friction of less than 0.03, which makes the tempered film surface more resistant to fingerprints and oil stains and easier to clean.

[0040] The glass processing steps are followed by an assembly step, which may include, for example, applying an adhesive layer to the back of the protective film glass, setting a pull strip layer on the adhesive layer, and assembling an applicator.

[0041] In the manufacturing process of flat-screen mobile phone protective films, it is necessary to ensure the protective film is as flat as possible to avoid warping. Furthermore, tempering requires heating the glass to a high temperature and then rapidly cooling it, creating surface compressive stress. Performing a polishing process after tempering may damage this surface compressive stress layer, leading to a decrease in glass strength and an increased risk of breakage. Therefore, conventional protective film processing usually only performs a polishing process before tempering. After tempering, if further improvements in glass quality are required, acid washing or other steps are typically used. However, since the protective film component in this embodiment is mainly used to protect the screen of tablet computers, which are typically used less frequently than mobile phones, damage to the screen primarily comes from scratches during use and from scratches or bumps caused by keys or other objects while stored. Therefore, the drop resistance requirements for the protective film glass are relatively low. Therefore, in this embodiment, a second polishing process is added after tempering to destroy the compressive stress layer on the back of the protective film glass. This causes the back of the protective film glass to be concave after the compressive stress layer is removed, and the warping of the protective film glass is controlled to be greater than or equal to 0.8mm to avoid bubble formation and improve the success rate of film application.

[0042] In some embodiments, the tempering temperature is 380℃~410℃, and the tempering time is 2~3 hours. More specifically, the tempering temperature is 410℃, and the tempering time is 2 hours. Alternatively, the tempering temperature is 380℃, and the tempering time is 3 hours. In this embodiment, by using a higher tempering temperature and duration, a certain degree of warpage can be pre-established during the tempering process, which can reduce the time required for the subsequent second polishing process to reach the target warpage and reduce the impact of the second polishing process on the glass strength.

[0043] In some embodiments, the pressure applied to the front surface of the glass during the second polishing process is 2~4 kg / cm². 2 The polishing time is 10-15 seconds. Choosing an appropriate polishing time can ensure sufficient polishing time to achieve the target warp, while avoiding excessive deformation and distortion of the glass due to excessive polishing time.

[0044] In some embodiments, the glass is float glass, the front side is the air surface of the float glass, and the back side is the tin side of the float glass. Using the air surface of the float glass as the front side can accommodate the characteristic of the air surface arching during the tempering process of float glass, and can better meet the requirements of warpage.

[0045] Experiments 1 to 14 verified the effects of different glass processing techniques on the resulting tempered glass. The process steps for Experiments 1 to 4 included steps (1) to (3) of the aforementioned glass processing steps: blanking and CNC edge grinding → first polishing → tempering, without step (4) second polishing. The process steps for Experiments 5 to 14 included steps (1) to (4) of the aforementioned glass processing steps: blanking and CNC edge grinding → first polishing → tempering → second polishing. Compared to Experiments 1 to 4, Experiments 5 to 14 only added a second polishing step. The parameters for the tempering and second polishing in Experiments 1 to 14 are shown in Table 1, and the other process parameters are the same.

[0046] Table 1

[0047] Five tempered glass films were randomly selected from each of Experiments 1 to 14 to check their warpage. The results are shown in Table 2. In Table 2, warpage 1 to warpage 5 refer to the warpage of each of the five tempered glass films (unit: mm). NG indicates failure, and PASS indicates success. The glass size used corresponds to a 13-inch iPad screen. The glass is float glass, with the air gap on the front, and a thickness of 0.33 mm.

[0048] Table 2

[0049] According to Table 2, experiments 1 to 4 did not undergo a second light-scanning process. Although the tempering process caused some warpage, the warpage was between 0.35 and 0.55 mm, failing to meet the requirement of greater than or equal to 0.8 mm. The tempering temperature of Experiment 1 was higher than that of Experiment 2, and the tempering temperature of Experiment 4 was higher than that of Experiment 2. Increasing the tempering temperature could achieve a higher warpage. Experiment 5 added a second light-scanning process compared to Experiment 1, which increased the warpage, but could not completely guarantee a warpage greater than or equal to 0.8 mm. Experiment 6 increased the duration of the second light-scanning process compared to Experiment 5, further improving the warpage to over 1 mm. Experiments 7 and 8 further increased the duration of the second light-scanning process compared to Experiment 6. Although the warpage increased, the tempered glass ultimately deformed and twisted, failing to adhere flatly to the screen, thus failing the test. Experiment 9 added a second light-scanning process compared to Experiment 2, improving the warpage, but still could not guarantee that all warpages would reach 0.8 mm. Experiment 9 had a lower tempering temperature than Experiment 5, and its warpage was also slightly lower. Experiment 10, compared to Experiment 9, further increased the second light-scanning time, resulting in a further improvement in warpage, reaching 0.8~0.9mm. Experiment 10 had a lower tempering temperature than Experiment 6, therefore its warpage was also lower. Experiment 11, compared to Experiment 9, increased the tempering time but did not increase the second light-scanning time, resulting in virtually no improvement in warpage. Experiment 12, compared to Experiment 11, increased the second light-scanning time, achieving a warpage of 0.8mm. Experiment 13, compared to Experiment 5, only increased the tempering time, but the second light-scanning time was still too short to achieve a warpage of 0.8mm. Experiment 14, compared to Experiment 6, only increased the tempering time, and compared to Experiment 13, only increased the second light-scanning time. Although the warpage improved, it ultimately deformed and twisted, failing to adhere flatly to the screen, and therefore failed.

[0050] The results in Table 2 confirm that the optimal duration for the second light-scanning process is 10-15 seconds, which is compatible with tempering parameters of 380℃ / 2h, 410℃ / 2h, and 380℃ / 3h. The optimal tempering parameter is 410℃ / 2h, which achieves a warpage of approximately 1mm. This ensures effective air venting, prevents bubble trapping, and avoids distortion of the tempered glass, guaranteeing a smooth and even fit with the screen.

[0051] The tempered glass screen protector obtained in Experiment 6 was assembled with upper protective layers of different thicknesses and adhesive strengths to obtain the protective film assembly, including an applicator and a pull-tab type protective film, provided in the above embodiments of this application. The film was then applied to a 13-inch iPad. The experimental results are shown in Table 3.

[0052] Table 3

[0053] The calculation method for the success rate of screen protector application in Table 3 is as follows: When visible air venting problems such as trapped bubbles in the middle or bubbles at the tail appear after the screen protector is applied, the application is considered a failure. The success rate of screen protector application = (total number of screen protectors applied - number of failures) / total number of screen protectors applied * 100%.

[0054] According to the experimental results in Table 3, when the adhesive strength is 5-8g, a protective layer thickness of 0.125-0.145mm can achieve a film application success rate of over 60%. The highest success rate is achieved with a protective layer thickness of 0.125mm. When the adhesive strength is 8-15g, a protective layer thickness of 0.25mm achieves a success rate of over 60%. Considering cost, a protective layer thickness of 0.125-0.145mm is preferred.

[0055] Furthermore, it is understood that the foregoing embodiments are merely illustrative examples of the present invention. Provided that the technical features do not conflict, the structure is not contradictory, and the purpose of the invention is not violated, the technical solutions of the various embodiments can be arbitrarily combined and used.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A protective film assembly for an electronic device, characterized in that, The protective film assembly includes a pull-tab type protective film, which includes: a protective film glass, an adhesive layer disposed on the reverse side of the protective film glass, and a pull-tab layer disposed on the side of the adhesive layer away from the protective film glass; the warpage of the protective film glass is greater than or equal to 0.8 mm and the reverse side is concave.

2. The protective film assembly for an electronic device as claimed in claim 1, characterized in that, The reverse side of the protective film glass is gradually concave from both ends toward the middle along its length.

3. The protective film assembly for an electronic device as claimed in claim 1, characterized in that, The warpage of the protective film glass is less than or equal to 1.5 mm.

4. The protective film assembly of the electronic device as described in any one of claims 1 to 3, characterized in that, The protective film assembly also includes an applicator; the front side of the protective film glass is also provided with an upper protective layer, the edge of the upper protective layer extends out of the protective film glass and is fixedly connected to the applicator; the upper protective layer includes a substrate and an adhesive disposed on the surface of the substrate, the adhesive is bonded to the front side of the protective film glass, and the adhesive has a stickiness of 5~8g.

5. The protective film assembly for an electronic device as described in claim 4, characterized in that, The thickness of the upper protective layer is 0.125~0.145mm.

6. A preparation method, characterized in that, A protective film assembly for preparing an electronic device as described in any one of claims 1 to 5; the preparation method includes a glass processing step, the glass processing step specifically including: (1) Cut the glass and perform CNC edge grinding; (2) After CNC edge grinding, perform the first polishing treatment on the front of the glass; (3) Tempering is performed after the first polishing process; (4) After tempering, the front of the glass is polished a second time.

7. The preparation method according to claim 6, characterized in that, The tempering process is carried out at a temperature of 380℃ to 410℃ for 2 to 3 hours.

8. The preparation method according to claim 7, characterized in that, The tempering process is performed at a temperature of 410°C for 2 hours; or at a temperature of 380°C for 3 hours.

9. The preparation method according to claim 6, characterized in that, The pressure applied to the front of the glass during the second polishing process is 2~4 kg / cm². 2 The duration is 10-15 seconds.

10. The preparation method according to claim 6, characterized in that, The glass is float glass, the front side is the air side of the float glass, and the back side is the tin side of the float glass.

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