Film application method

Abstract

The present invention provides a film application method that can suitably adhere a film to a substrate. [Solution] The present invention is a method for attaching a film 20 to an object to be attached 10, wherein a film is prepared in which an adhesive layer 22 is formed on the attachment side surface 21 and a protective film 23 is attached to the surface of the adhesive layer; a first mold 30 and a second mold 40 are prepared, each having a cavity substantially matching the surface shape of the object to be attached; the film is sandwiched between the molds; the molds are heated together with the film to a first temperature, then cooled to a second temperature; the pre-formed film is removed; the object to be attached and the film are placed in a predetermined atmosphere; the protective film on the object to be attached is peeled off from the pre-formed film; the film is placed facing the object to be attached, and a pressing jig 50 having a lower hardness than the film is pressed against the film to attach the film to the object to be attached.

Description

Technical Field

[0001] The present invention relates to a method for attaching a film to an adherend such as a lens.

Background Art

[0002] A functional thin film such as a polarizing film is attached to a curved lens such as an optical lens, a liquid crystal panel, or other functional substrates and devices to ensure and improve functionality, surface protection, and the like.

[0003] For example, Patent Document 1 discloses a film sticking device in which a lens to be an adherend is accommodated in a chamber having an open upper surface so as to be vertically movable, and a film hermetically attached to the opening. The sticking device preliminarily forms the film into a curvature equivalent to that of the lens by increasing or decreasing the air pressure in the chamber and using the air differential pressure with the atmosphere. Then, the lens is pressed against the curved film for attachment.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, it is very difficult to bend the film to match the curvature of the lens only by the air differential pressure. Also, with only the air differential pressure, the film cannot be preformed to match an adherend with a changing curvature or an adherend with irregularities during the process, so the applications are limited.

[0006] An object of the present invention is to provide a film sticking method capable of suitably sticking a film to an adherend.

Means for Solving the Problems

[0007] The film application method of the present invention is A method for attaching a film to an object to be covered, A film is prepared in which an adhesive layer is formed on the adhesive side facing the object to be adhered, and a protective film is attached to the surface of the adhesive layer. A first mold and a second mold are prepared, each having a cavity that substantially matches the surface shape of the object to be bonded. The film is sandwiched between the first mold and the second mold, the first mold and the second mold are heated together with the film to a first temperature, then cooled to a second temperature while being clamped with a predetermined stress, the first mold and the second mold are opened, and the pre-formed film is removed. The object to be bonded and the film are placed in a predetermined atmosphere. The protective film on the side to be adhered to is peeled off from the pre-formed film. The film is placed opposite the object to be adhered to, and a pressing jig with a lower hardness than the film is pressed against the film to adhere it to the object.

[0008] The object to be bonded can have a curved shape.

[0009] It is desirable that the curvature of the cavity is smaller than the curvature of the material to be bonded.

[0010] The curvature of the cavity is preferably 5% to 20% smaller than the curvature of the material to be bonded.

[0011] The pressing jig is preferably of durometer hardness 30 or less.

[0012] The aforementioned atmosphere is preferably 133.3 Pa or less.

[0013] The aforementioned film can be a polarizing film. [Effects of the Invention]

[0014] According to the film sticking method of the present invention, by pre-forming the film with the first mold and the second mold, the shape of the film can be made to conform to the shape of the adherend, and the film can be suitably stuck to the adherend with a pressing jig having a hardness lower than that of the film.

Brief Description of the Drawings

[0015] [Figure 1] FIG. 1 is a perspective view of (a) a lens to be an adherend and (b) a film. [Figure 2] FIG. 2 is a perspective view of the pre-formed film. [Figure 3] FIG. 3 is a photograph of the first mold, the second mold, and the film. [Figure 4] FIG. 4 is an explanatory view showing the pre-forming process of the film. [Figure 5] FIG. 5 is a photograph showing the process of removing the pre-formed film from the mold. [Figure 6] FIG. 6 is a photograph of the pre-formed body of the film. [Figure 7] FIG. 7 is an explanatory view showing the film sticking process. [Figure 8] FIG. 8 is an explanatory view showing the film sticking process following FIG. 7.

Embodiments for Carrying Out the Invention

[0016] Hereinafter, a method for sticking a film 20 according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, for easy understanding, dimensions, particularly the thickness of the film and the thickness of the lens, are exaggerated.

[0017] The present invention relates to a method for sticking a film 20 having functionality such as a polarizing film to the surface of an adherend 10 such as a curved lens such as an optical lens, a liquid crystal panel, or other functional substrates and devices. In the present embodiment, a lens is adopted as the adherend 10, and the film 20 is a polarizing film, but it is not limited thereto.

[0018] The adherend 10 can be a member having a concavo-convex shape. For example, as the adherend 10, a lens as shown in Fig. 1(a) can be lifted. The lens is composed of a light-transmitting member such as transparent resin or glass. In the drawing, one surface has a convex curved surface shape and the other surface is a flat convex lens. In the present embodiment, the convex shape side of the lens is the film attachment surface 11, and the film 20 is attached thereto.

[0019] As shown in Fig. 1(b), the film 20 is a thin film body and has a polarizing function and a lens protection function. As the polarizing film, iodine-based and dye-based films are known. In the iodine-based film, plastics such as PVA (polyvinyl alcohol) are stretched, the molecular orientation is aligned, and iodine is bonded to make it polarizable. The thickness of the film 20 is not limited, but a film having a thickness of 50 μm or less is preferable, and 25 μm to 35 μm is desirable. Note that the film 20 can be configured such that TAC (triacetate cellulose film) is laminated on the surface of PVA.

[0020] Alternatively, the film 20 may be TAC alone, PET (polyethylene terephthalate), or the like.

[0021] At least a protective film 23 is attached to the surface of the film 20 to be attached to the adherend 10, that is, the attachment side surface 21 facing the adherend 10 during attachment, via an adhesive layer 22. As the adhesive layer 22, PSA (pressure sensitive adhesive) can be exemplified. When attaching the film 20, the protective film 23 is removed to expose the adhesive layer 22. The protective film 23 is, for example, PET and has a thickness of 30 μm to 40 μm.

[0022] As shown in Figure 2, the film 20 is pre-formed to match the shape of the object to be bonded 10. Specifically, if the object to be bonded 10 is a convex lens, a pre-formed body 24 is created that is curved into a convex shape to match the curvature of the lens. Rather than making the film 20 the same shape as the film bonding surface 11 of the object to be bonded 10, it is desirable to curve it so that the curvature is 5% to 20% smaller than the curvature of the object to be bonded 10, preferably 7% to 15% smaller. This is because, as shown in Figure 8 later, when pressing the film 20 onto the object to be bonded 10, the film 20 and the object to be bonded 10 come into contact sequentially from the top, allowing the pressing force of the pressing jig 50 to be applied to the film 20 appropriately, and also to suppress the retention of air bubbles.

[0023] Furthermore, if the curvature of the film 20 is less than 5% smaller than that of the object to be adhered to 10, the curvatures of the film 20 and the object to be adhered to 10 are almost the same, so when the film 20 is pressed against the object to be adhered to 10, air bubbles tend to remain between them. On the other hand, if the curvature of the film 20 is more than 20% larger than that of the object to be adhered to 10, even if the film 20 is pressed against the object to be adhered to 10 using the pressing jig 50, the film 20 may not conform well to the shape of the object to be adhered to 10, resulting in sagging or wrinkles. Therefore, in the present invention, the film 20 is curved to have a curvature that is about 5% to 20% smaller than the curvature of the object to be adhered to 10, preferably about 7% to 15% smaller.

[0024] A pre-molded body 24 can be created by pressing a film 20 between a pair of molds 30 and 40. As shown in Figure 3, the molds 30 and 40 can consist of a first mold 30 and a second mold 40, each having a cavity that matches the shape and thickness of the film 20 to the surface shape of the object to be bonded 10. The material of the molds 30 and 40 is preferably aluminum or stainless steel, which have excellent thermal conductivity. When the object to be bonded 10 is a convex lens, as shown in the figure, the first mold 30 is concave and the second mold 40 is convex. In the illustrated embodiment, an air hole 43 is provided through the top of the second mold 40 to prevent the retention of air bubbles when the film 20 is pressed. Of course, an air hole can also be provided in the first mold.

[0025] As mentioned above, it is desirable that the film 20 has a curvature smaller than the curvature of the object to be bonded 10. For this reason, the first mold 30 and the second mold 40, which create the pre-molded body 24 of the film 20, are set so that the curvature of the cavity in which the film 20 is formed is smaller than the curvature of the surface shape of the object to be bonded 10.

[0026] As shown in Figure 3, the molds 30 and 40 can be configured to have flange portions 31 and 41 that widen toward the outer circumference. These flange portions 31 and 41 have screw holes 32 and 42 formed at locations where they coincide when the molds 30 and 40 are positioned together and when they are stacked during clamping. The molds 30 and 40 are fastened together with bolts 34 (see also Figure 5).

[0027] Figure 4 is an explanatory diagram showing the process of forming a pre-molded body 24 of the film 20, where the molds 30 and 40 have a flat cross-section at the top. As shown in Figure 4(a), the flat film 20 before pre-molding is placed between the first mold 30 and the second mold 40, with the second mold 40 side becoming the adhesive side 21. It is desirable to form the film 20 slightly larger than the molds 30 and 40 and to apply tension to the periphery by pulling it outward with a jig (not shown). For example, in the case of a PVA film 20 with a thickness of 25 μm to 35 μm, the tension is preferably 15 N to 20 N. In a specific embodiment, the tension applied to PVA with a thickness of 25 μm to 35 μm is 18 N.

[0028] In this state, as shown in Figure 4(b), the molds 30 and 40 and the film 20 are placed in a heating device and heated to a first temperature. The first temperature is a temperature at which the film 20 can be heat-bent without losing its functionality, and is set appropriately depending on the material and thickness of the film 20. For example, in the case of PVA with a thickness of 25 μm to 35 μm, the first temperature is 100°C to 130°C, and the heating time is 1 second to 10 seconds. In a specific embodiment, the first temperature for PVA with a thickness of 25 μm to 35 μm is 120°C, and the heating time is 2 seconds.

[0029] Once the heating of the molds 30, 40 and the film 20 is complete, the molds 30 and 40 are brought closer together from above and below the film 20, as shown by the arrows in Figure 4(c), while tension is still applied to the film 20, and the screw holes 32 and 42 are aligned and secured with bolts 34 to clamp the mold. Because the film 20 is thin, the bolts 34 penetrate the film 20. As a result, the film 20 deforms along the cavity between the first mold 30 and the second mold 40. For example, if air remains between the second mold 40 and the film 20, the air is released from the outer circumference of the second mold 40 or from the air holes 43 due to the clamping pressure.

[0030] Then, with the molds clamped, the molds 30, 40 and the film 20 are cooled to a second temperature. The second temperature is, for example, room temperature (20°C to 30°C). In this step, the film 20 may be compressed in a heating device, and after compression is complete, it may be removed from the heating device and cooled.

[0031] The tension applied to the film 20 may be released after the molds 30 and 40 are secured with bolts 34.

[0032] Once the molds 30, 40 and the film 20 have cooled to a second temperature, the bolts 34 are removed, the molds 30, 40 are opened, and the film 20 is removed as shown in Figure 4(d). The film 20 is pre-formed by the molds 30, 40 and stabilizes in a shape that conforms to the surface shape of the object to be bonded 10, as shown in Figure 2.

[0033] Figure 5 shows the molds 30 and 40 in the open state, with the film 20 overlapping the first mold 30. The film 20 has an unnecessary outer peripheral portion 25 on its outer edge that will be trimmed in a later process.

[0034] Figure 6 is a photograph of the pre-molded body 24 of the film 20 removed from the molds 30 and 40, with the convex side facing up on the left and the concave side facing up on the right. Referring to the figure, it can be seen that a curved surface conforming to the shape of the object to be bonded 10 has been formed in the center of the film 20.

[0035] Next, the resulting pre-molded film 20 and the object to be bonded 10 are placed in a predetermined atmosphere, and the film 20 bonding process is carried out. The predetermined atmosphere is a space with reduced pressure or a vacuum atmosphere, where the reduced pressure is preferably 1 torr (133.3 Pa) or less, and preferably 100 Pa or less. In the atmosphere, temperature, humidity, and dust are controlled under reduced pressure to avoid the inclusion of air bubbles and dust when bonding the film 20. For example, the film 20 bonding process can be carried out in a reduced pressure chamber.

[0036] Figures 7 and 8 are explanatory diagrams of the film 20 application process. Prior to the application process, the outer peripheral portion 25 that is not needed for application is trimmed from the film 20, as shown in the lower part of Figure 7(a).

[0037] The application process involves placing the film 20 and the object to be applied 10 in a vacuum chamber that can be adjusted to the predetermined atmosphere (Figure 7(b)), and adjusting the pressure inside the chamber to the predetermined atmosphere. Then, as shown in Figure 7(c), the protective film 23 on the application side 21 is peeled off the film 20. This exposes the adhesive layer 22 on the application side 21 of the film 20. The protective film 23 can be removed by making a cut and rolling it up.

[0038] Next, as shown in Figure 8(a), the object to be adhered 10 and the film 20 are aligned vertically. The film 20 is positioned so that the adhesive side 21 faces the object to be adhered 10, and the object to be adhered 10 is positioned so that the film adhesive side 11 faces the film 20. In this embodiment, the film 20 is curved to a curvature that is 5% to 20% smaller than the curvature of the object to be adhered 10, so as shown in the figure, the film 20 is less curved than the object to be adhered 10.

[0039] In this state, the film 20 is pressed against the object to be bonded 10. As shown in Figures 8(a) to (c), a pressing jig 50 can be used to press the film 20. The pressing jig 50 is a jig with a lower hardness than the film 20, and is made of an elastic material such as silicone rubber, urethane rubber, other soft rubbers, or sponge. The hardness of the pressing jig 50 should preferably be around 5 to 30 as measured by a durometer (rubber hardness tester) with a C hardness tester. The hardness of the film 20 is approximately 5 for PVA with a thickness of 25 μm to 35 μm.

[0040] The pressing conditions for the pressing jig 50 can be set to a pressing rate of 2 mm / sec to 15 mm / sec and a pressing pressure of 0.1 MPa to 1.0 MPa. If the film 20 is PVA with a thickness of 25 μm to 35 μm, the pressing rate can be set to 8 mm / sec, the pressing pressure to 0.5 MPa, and the pressing time to 3 sec.

[0041] By pressing the pressing jig 50 onto the film 20, as shown in Figure 8(a), the inner surface of the top of the film 20 comes into contact with the top of the object to be bonded 10, and the adhesive layer 22 in that portion adheres to the object to be bonded 10. Since the film 20 has a smaller curvature than the object to be bonded 10, when the tops of the film 20 and the object to be bonded 10 come into contact, other parts are not yet in contact.

[0042] From this state, the pressing jig 50 is further pressed against the film 20, as shown by the arrows in Figures 8(b) and (c). As a result, as shown in Figure 8(b), the pressing jig 50 elastically deforms, pushing out the air between the film 20 and the object to be adhered to 10, and pressing the film 20 sequentially against the object to be adhered to 10 toward the periphery of the top. As the film 20 is pressed against the object to be adhered to 10, the adhesive layer 22 adheres to the object to be adhered to 10. Finally, as shown in Figure 8(c), the film 20 can be adhered to the object to be adhered to 10 by pressing the pressing jig 50 until the film 20 is completely adhered along the object to be adhered to 10.

[0043] After the film 20 is attached to the object to be attached 10, the pressing force of the pressing jig 50 is released, and the object to be attached 10 with the film 20 attached is removed from the chamber. Figure 8(d) shows the object to be attached 10 with the film 20 attached.

[0044] According to the present invention, a pre-molded body 24 is formed in advance by curving the film 20 to match the shape of the object to be bonded 10, and the film 20 is pressed onto the object to be bonded 10 with a pressing jig 50 that has a lower hardness than the film 20, thereby suppressing the retention of air bubbles and allowing the film 20 to be suitably bonded to the object to be bonded 10.

[0045] The above description is for the purpose of explaining the present invention and should not be interpreted as limiting or restricting the scope of the invention described in the claims. Furthermore, it goes without saying that the configuration of each part of the present invention is not limited to the above embodiments and can be modified in various ways within the technical scope described in the claims.

[0046] For example, if the object to be bonded 10 has an uneven surface, the first mold 30 and the second mold 40 should form cavities that match the shape of the uneven surface, preferably cavities with a curvature smaller than that of the object to be bonded 10.

[0047] Furthermore, in the above embodiment, the contact surface of the pressing jig 50 with the film 20 is flat, as shown in Figure 8. However, by making the jig conform to the surface shape of the object to be bonded 10, the film 20 can be pressed evenly. Specifically, if the object to be bonded 10 is a convex lens, the pressing jig 50 should have a concave curved surface. [Explanation of Symbols]

[0048] 10. Object to be attached (lens) 20 film 30 First mold 40. Second mold 50 Pressing jig

Claims

1. A method for attaching a film to an object to be covered, A film is prepared in which an adhesive layer is formed on the adhesive side facing the object to be adhered, and a protective film is attached to the surface of the adhesive layer. A first mold and a second mold are prepared, each having a cavity that substantially matches the surface shape of the object to be bonded. The film is sandwiched between the first mold and the second mold, the first mold and the second mold are heated together with the film to a first temperature, then cooled to a second temperature while being clamped with a predetermined stress, the first mold and the second mold are opened, and the pre-formed film is removed. The object to be bonded and the film are placed in a predetermined atmosphere. The protective film on the side to be adhered to is peeled off from the pre-formed film. The film is placed facing the object to be adhered to, and a pressing jig less hard than the film is pressed against the film to adhere it to the object. Film application method.

2. The object to be bonded has a curved shape. The method for applying a film according to claim 1.

3. The curvature of the cavity is smaller than the curvature of the material to be bonded. The method for applying a film according to claim 2.

4. The curvature of the cavity is 5% to 20% smaller than the curvature of the material to be bonded. The method for applying a film according to claim 3.

5. The aforementioned pressing jig has a durometer hardness of 30 or less. The method for applying a film according to claim 4.

6. The aforementioned predetermined atmosphere is 133.3 Pa or less. The method for applying a film according to claim 5.

7. The aforementioned film is a polarizing film. The method for applying a film according to claim 6.

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