protective film

Abstract

To provide a protective film which is excellent in such re-adhesion as to be stuck to a resin substrate, then at least partially peeled, and then be stuck to the resin substrate again.SOLUTION: A protective film 10 is stuck to a resin substrate 21 and used when the resin substrate 21 is thermally bent, and has a base material layer and an adhesive layer which is positioned between the base material layer and the resin substrate, and is bonded to the resin substrate, wherein the base material layer is composed of a laminate having a first layer positioned on a side opposite to the adhesive layer and a second layer positioned on the adhesive layer side, and the adhesive layer has surface roughness Ra on a surface on the side of the resin substrate 21, which is measured according to JIS B 0601, of 0.20 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a protective film that is attached to a resin substrate when the resin substrate is subjected to a heat bending process under heating. [Background technology]

[0002] Sunglasses lenses equipped with a resin substrate configured by covering both sides of a polarizer with coating layers made of polycarbonate resin, polyamide resin, or cellulose resin are manufactured, for example, by punching the resin substrate into a predetermined shape, such as a circle, in a planar view with protective films attached to both sides of the resin substrate, which is flat in a planar view, and then subjecting the resin substrate to a heat-bending process under heating.The protective films are then peeled off from the heat-bent resin substrate, and a polycarbonate layer is injection-molded onto the concave surface of the resin substrate.

[0003] As this protective film, for example, a configuration has been proposed in which a base material primarily made of polyolefin resin is attached to the resin substrate via an adhesive layer primarily made of polyethylene, ethylene-propylene copolymer, etc. (see, for example, Patent Document 1).

[0004] As described above, the protective films are attached to both sides of the resin substrate prior to punching the resin substrate, and this attachment is usually performed by hand or by using an arm provided on a machine tool, etc. During attachment of the protective film, due to the occurrence of wrinkles in the protective film or the presence of air bubbles between the protective film and the resin substrate, it may be necessary to peel at least a portion of the protective film from the resin substrate once, and then reattach (re-adhere) the peeled protective film to the resin substrate.

[0005] However, with a protective film having the above-described configuration, it is not possible to obtain sufficient re-adhesion properties when the protective film is re-attached to a resin substrate after being peeled off from the resin substrate, and therefore there has been a demand for the development of such a protective film with excellent re-adhesion properties.

[0006] This problem occurs not only in the above-mentioned sunglasses lenses, but also in resin substrates such as lenses provided in goggles and visors provided in helmets. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-145616 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a protective film that has excellent re-adhesion properties and that can be attached to a resin substrate, at least a portion of which can then be peeled off, and then re-attached to another resin substrate. [Means for solving the problem]

[0009] Such objectives are as follows: (1) 8 This is achieved by the present invention described in (1) A protective film to be attached to a resin substrate when the resin substrate is subjected to a heat bending process under heating, a substrate layer; an adhesive layer positioned between the base layer and the resin substrate and adhering to the resin substrate; the base layer is composed of a laminate having a first layer located on the opposite side of the adhesive layer and a second layer located on the adhesive layer side, The adhesive layer has a surface roughness Ra of 0.20 μm or less on the surface on the resin substrate side, as measured in accordance with JIS B 0601.the law of nature, In accordance with JIS K 7127, a test piece (No. 1 dumbbell) taken from the protective film was measured at a tension speed of 500 mm / min using a Shimadzu autograph under an atmosphere of 23°C and 60% RH, and the modulus of elasticity was 300 MPa or more and 600 MPa or less. A protective film characterized by:

[0011] ( 2 The first layer is made of a thermoplastic resin as a main material and has a melting point of 150°C or higher, the second layer is made of a thermoplastic resin as a main material and has a melting point of 120°C or higher, and the adhesive layer is made of a thermoplastic resin as a main material and has a melting point of 110°C or lower. (1) The protective film according to claim 1.

[0012] ( 3 The thermoplastic resin contained in the first layer and the thermoplastic resin contained in the second layer both contain polyolefin-based resins. 2 ) The protective film described in

[0013] ( 4 The adhesive layer is a layer of the adhesive composition according to any one of (1) to (3) above, which contains a polyolefin resin having adhesive properties as a main material. 3 ) The protective film according to any one of the preceding claims.

[0014] ( 5 ) A protective film measuring 25 mm wide x 200 mm long is applied to a polycarbonate substrate, and then, in an environment of 25°C, one end of the protective film is held and peeled off in a 90° direction to a position 100 mm long. After that, the protective film is reapplied to the polycarbonate substrate by releasing the one end of the protective film. One minute after reapplication, the total area in a plan view of the area where the polycarbonate substrate and the protective film are not bonded is 1250 mm 2 The above (1) to ( 4 ) The protective film according to any one of the preceding claims.

[0015] ( 6 ) The above (1) to ( 5 ) The protective film according to any one of the preceding claims.

[0016] (7 ) The resin substrate has a coating layer on both sides, one side or the other side, which is composed of a single layer or a laminate having at least one layer selected from the group consisting of a polycarbonate resin layer, a polyamide resin layer and a cellulose resin layer, as described in (1) to ( 6 ) The protective film according to any one of the preceding claims.

[0017] ( 8 The resin substrate is subjected to the heat bending process by press molding or vacuum molding. 7 ) The protective film according to any one of the preceding claims. [Effects of the Invention]

[0018] According to the present invention, the adhesive layer of the protective film has a surface roughness Ra of 0.20 μm or less on the surface facing the resin substrate, measured in accordance with JIS B 0601. By setting the surface roughness Ra of the adhesive layer on the surface facing the resin substrate to the upper limit or less, the protective film can be made to have excellent re-adhesion properties when it is attached to a resin substrate, at least a portion of it is then peeled off, and then it is attached again to the resin substrate. [Brief explanation of the drawings]

[0019] [Figure 1] 1A and 1B are schematic diagrams for explaining a method for manufacturing a sunglass lens using a protective film. [Figure 2] 10A and 10B are schematic diagrams illustrating a method of peeling off at least a portion of a protective film attached to a resin substrate and then attaching the protective film to the resin substrate again. [Figure 3] 1 is a longitudinal sectional view showing a preferred embodiment of a protective film of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The protective film of the present invention will be described in detail below with reference to preferred embodiments shown in the accompanying drawings. In this specification, the term "main material" refers to a constituent material that accounts for 50% by weight or more of each layer. For example, "the first layer 16 contains a thermoplastic resin as its main material" means that, when the total weight of the first layer 16 is 100% by weight, the thermoplastic resin contained in the first layer 16 accounts for 50% by weight or more of the first layer 16.

[0021] The protective film of the present invention is a protective film that is attached to a resin substrate when the resin substrate is subjected to a thermal bending process under heating, and has a base layer and an adhesive layer that is located between the base layer and the resin substrate and adheres to the resin substrate, the base layer being composed of a laminate having a first layer located on the opposite side of the adhesive layer and a second layer located on the adhesive layer side, and the adhesive layer is characterized in that the surface roughness Ra of the surface on the resin substrate side, measured in accordance with JIS B 0601, is 0.20 μm or less.

[0022] By configuring the protective film in this manner, i.e., by setting the surface roughness Ra of the surface of the adhesive layer of the protective film facing the resin substrate to be equal to or less than the upper limit value, the protective film can be made to have excellent re-adhesion properties when it is attached to a resin substrate, then at least a portion of it is peeled off, and then it is attached again to the resin substrate.

[0023] Before describing the protective film of the present invention, a method for producing sunglasses lenses using the protective film of the present invention will be described below.

[0024] <Sunglasses lens manufacturing method> Fig. 1 is a schematic diagram illustrating a method for manufacturing a sunglass lens using a protective film, and Fig. 2 is a schematic diagram illustrating a method for peeling off at least a portion of a protective film attached to a resin substrate and then attaching it again to the resin substrate. Note that, for convenience of explanation, the upper side of Fig. 1 and Fig. 2 will be referred to as "upper" and the lower side as "lower" below.

[0025] Each step in the manufacturing method for sunglasses lenses will be described in detail below. [1] First, a flat resin substrate 21 is prepared, and protective films 10 (masking tape) are attached to both sides of the resin substrate 21 to obtain a laminate 100 in which protective films 10 are attached to both sides of the resin substrate 21 (see Figure 1(a)).

[0026] In this embodiment, the resin substrate 21 is prepared by covering both sides of a polarizer 23 that functions as an optical element that extracts linearly polarized light having a polarization plane in a predetermined direction from unpolarized natural light with a coating layer 24. In the resin substrate 21, the coating layer 24 is made of a single layer or a laminate having at least one layer selected from a polycarbonate resin layer, a polyamide resin layer, and a cellulose resin layer such as triacetyl cellulose, and the coating layer 24 may be formed on both sides (both surfaces) of the polarizer 23, or may be formed on either the top surface (one surface) or the bottom surface (the other surface).

[0027] [2] Next, as shown in FIG. 1(b), the prepared laminate 100, i.e., the resin substrate 21 with the protective film 10 attached to both sides thereof, is punched out in the thickness direction, so that the laminate 100 has a circular shape in a plan view.

[0028] [3] Next, as shown in FIG. 1(c), the circular laminate 100 is subjected to a heat bending process under heating.

[0029] This hot bending process is usually carried out by press forming using a mold or vacuum forming (rema forming).

[0030] As described above, in this embodiment, the resin substrate 21 has the coating layer 24, and the coating layer 24 is composed of a single layer or a laminate having at least one layer selected from a polycarbonate resin layer, a polyamide resin layer, and a cellulose resin layer, so the heating temperature (forming temperature) of the laminate 100 (resin substrate 21) at this time is set to preferably about 110°C or higher and 160°C or lower, more preferably about 140°C or higher and 150°C or lower, taking into consideration the melting or softening temperature of the coating layer 24. By setting the heating temperature within this range, the resin substrate 21 can be brought into a softened or molten state and reliably heat-bent while preventing alteration or deterioration of the resin substrate 21.

[0031] [4] Next, as shown in Fig. 1(d), the protective film 10 is peeled off from the thermally bent resin substrate 21, i.e., the laminate 100, and then a polycarbonate layer 30 made of polycarbonate resin is injection molded onto the concave surface of the resin substrate 21. Note that instead of the polycarbonate layer 30, a polyamide layer made of polyamide resin may be formed on the concave surface of the resin substrate 21.

[0032] In this way, the sunglass lens 200 including the thermally bent resin substrate 21 is manufactured.

[0033] Here, in the manufacturing method for sunglasses lenses as described above, prior to punching out the resin substrate 21 in the thickness direction in step [2], in step [1], protective films 10 are attached to both sides of the resin substrate 21, thereby obtaining a laminate 100 in which protective films 10 are attached to both sides of the resin substrate 21.

[0034] The application of the protective film 10 to this laminate 100 is usually carried out by hand or using an arm provided on a machine tool, but during this process, wrinkles may occur in the protective film 10 or air bubbles may remain between the protective film 10 and the resin substrate 21.

[0035] In this case, as shown in FIG. 2(a), one end of the protective film 10 in a laminate 100 in which the protective film 10 is attached to both sides of a resin substrate 21 is grasped, and then, as shown in FIG. 2(b), the protective film 10 is peeled off from this end to partway, thereby partially peeling off the protective film 10. Then, the gripping of the one end of the protective film 10 is released, and the peeled protective film 10 is again attached to the resin substrate 21, thereby re-attaching (re-adhering) the protective film 10 to the resin substrate 21, as shown in FIG. 2(c). However, when the protective film 10 is re-attached to the resin substrate 21 in this manner, there is a problem in that the adhesion of the protective film 10 to the resin substrate 21 is not sufficient compared to when the protective film 10 was attached to the resin substrate 21 the first time.

[0036] As a result of the inventor's investigation into this problem, it was found that the re-adhesion of a protective film 10 to a resin substrate 21 once peeled off is closely related to the surface properties of the adhesive layer 11 on the side opposite the base material layer 15 of the adhesive layer 11 of the protective film 10, i.e., the surface on the resin substrate 21 side of the adhesive layer 11.

[0037] The inventor then conducted further research into the relationship between the re-adhesion of the protective film 10 and the surface properties of the surface of the adhesive layer 11 facing the resin substrate 21, and discovered that by setting the surface roughness Ra of the surface of the adhesive layer 11 facing the resin substrate 21 to 0.20 μm or less, the protective film 10, once peeled off, exhibits excellent re-adhesion to the resin substrate 21, thereby completing the present invention.

[0038] Therefore, by using the protective film of the present invention, in which the surface roughness Ra on the surface on the resin substrate 21 side is set to 0.20 μm or less, as the protective film 10 and re-attaching the protective film 10, it is possible to appropriately suppress or prevent the protective film 10 and, ultimately, the resin substrate 21 from being wasted. As a result, the sunglass lenses 200 can be manufactured with a good yield. This protective film 10 (protective film of the present invention) will be described in detail below.

[0039] <Protection film 10> 3 is a longitudinal cross-sectional view showing a preferred embodiment of the protective film of the present invention. For convenience of explanation, the upper side of FIG. 3 will be referred to as "top" and the lower side as "bottom."

[0040] The protective film 10 has a base material layer 15 and an adhesive layer 11 located between the base material layer 15 and the resin substrate 21 and adhering (bonding) to the resin substrate 21. As shown in FIG. 3, the base material layer 15 has a first layer 16 located on the opposite side of the adhesive layer 11, i.e., on the mold side, and a second layer 17 located on the adhesive layer 11 side, i.e., on the resin substrate 21 side.

[0041] Each of these layers will be described in detail below. <<Adhesive layer 11>> The adhesive layer 11 is located (interposed) between the base material layer 15 and the resin substrate 21 and adheres to the resin substrate 21, thereby joining the base material layer 15 to the resin substrate 21.

[0042] This adhesive layer 11 is preferably one that allows the punching and heat bending of the resin substrate 21 in steps [2] and [3] to be carried out without peeling the protective film 10 from the resin substrate 21, and that allows the peeling of the protective film 10 from the resin substrate 21 in step [4].

[0043] Furthermore, in the present invention, prior to the step [2], a protective film 10 that can exhibit excellent re-adhesion is used in the re-adhesion of the protective film 10 to the resin substrate 21, which is carried out as necessary.

[0044] From this perspective, the adhesive layer 11 preferably contains an adhesive thermoplastic resin as its main material, and more preferably contains a thermoplastic resin having a melting point of 110°C or less. By using such a material as the adhesive layer 11, the effect obtained by setting the surface roughness Ra of the adhesive layer 11 on the surface facing the resin substrate 21 to 0.20 μm or less, i.e., the effect that the protective film 10, once peeled, can be reattached to the resin substrate 21 with excellent re-adhesion, can be significantly exhibited. Furthermore, by containing a thermoplastic resin having a melting point of 110°C or less in the adhesive layer 11, the melting point of the adhesive layer 11 can be easily set to 110°C or less. This allows the adhesive layer 11 to have excellent flexibility in low temperature regions such as room temperature, thereby more significantly exhibiting the effect obtained by setting the surface roughness Ra to 0.20 μm or less. In other words, the protective film 10, once peeled, can be reattached to the resin substrate 21 with excellent re-adhesion. From the viewpoint of achieving this effect more significantly, the melting point of the adhesive layer 11 is preferably 110°C or lower, more preferably 100°C or lower, and even more preferably 70°C or higher and 95°C or lower.

[0045] Furthermore, it is preferable that the adhesive layer 11 contains a polyolefin-based resin alone as the thermoplastic resin, or a polyolefin-based resin and an elastomer in combination in the adhesive layer 11. By making the adhesive layer 11 contain such a thermoplastic resin, the above-mentioned effects can be more reliably exhibited.

[0046] The adhesive polyolefin resin is not particularly limited and may be, for example, a polypropylene homopolymer, a polyethylene homopolymer, a propylene-ethylene block copolymer having an EPR phase (rubber phase), an ethylene-vinyl acetate block copolymer, an ethylene-ethyl acrylate block copolymer, or an ethylene-methyl methacrylate block copolymer. One or more of these may be used in combination, and among these, a polyethylene homopolymer is preferred. Polyethylene homopolymers are relatively inexpensive, and those with a melting point of 110°C or less are also readily available. Furthermore, polyethylene homopolymers can impart transparency to the adhesive layer 11. Therefore, if the base layer 15 is also transparent, the protective film 10 will also be transparent. Therefore, when the protective film 10 is attached to the resin substrate 21 in step [1], and when the protective film 10 is reattached to the resin substrate 21 prior to step [2], it is possible to visually determine whether or not dust or other debris is present between the protective film 10 and the resin substrate 21, and this makes it possible to reliably prevent the laminate 100 containing debris from being transferred after step [2], thereby improving the yield of the sunglass lenses 200 obtained.

[0047] The polyethylene homopolymer is not particularly limited, but examples thereof include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), and very low-density polyethylene (VLDPE), and one or more of these may be used in combination.

[0048] The elastomer is not particularly limited, but examples thereof include α-polyolefin resin / polyethylene copolymer elastomer, α-polyolefin resin / polypropylene copolymer elastomer, and styrene block elastomer. Among these, styrene block elastomer is preferred, and styrene-olefin-styrene block copolymer elastomer is particularly preferred. By including an elastomer in addition to a polyolefin resin, the adhesive layer 11 remains on the resin substrate 21 when the protective film 10 is peeled from the resin substrate 21 in step [4]. This effectively suppresses or prevents adhesive residue on the resin substrate 21, allowing the protective film 10 to be peeled more smoothly from the resin substrate 21. Furthermore, by including styrene as a monomer component in the elastomer, the adhesive residue on the resin substrate 21 in step [4] can be effectively suppressed or prevented.

[0049] Examples of the α-polyolefin resin include 1-hexene, 4-methyl-1-pentene, 1-octene, 1-butene, 1-pentene, and 1-heptene.

[0050] Furthermore, when a styrene-olefin-styrene block copolymer elastomer is used as the elastomer, the styrene content in the elastomer is preferably 25% by weight or less, and more preferably 10% by weight or more and 18% by weight or less. This effectively suppresses or prevents an increase in the hardness of the adhesive layer 11, which would otherwise be caused by a high styrene content. Therefore, it is possible to more effectively suppress or prevent adhesive residue on the resin substrate 21 while reliably maintaining the adhesive strength of the adhesive layer 11 to the resin substrate 21 (coating layer 24).

[0051] Furthermore, examples of styrene-olefin-styrene block copolymers include styrene-isobutylene-styrene block copolymer (SIBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-butadiene-styrene block copolymer (SBS), and styrene-isoprene-styrene copolymer (SIS), among which styrene-ethylene-butylene-styrene block copolymer (SEBS) is preferred. By selecting SEBS as the styrene-olefin-styrene block copolymer, the styrene content in the elastomer can be easily set to 25% by weight or less, and the above-mentioned effects can be reliably obtained.

[0052] Furthermore, when the adhesive layer 11 contains an elastomer, the content of the elastomer in the adhesive layer 11 is not particularly limited, but is preferably set to 1% by weight or more and 30% by weight or less, and more preferably 5% by weight or more and 15% by weight or less, thereby making it possible to more significantly exhibit the effects obtained by including the elastomer in the adhesive layer 11.

[0053] As mentioned above, it is more preferable that the thermoplastic resin contains one having a melting point of 110° C. or less, but when adhesive layer 11 contains both a polyolefin resin and an elastomer as thermoplastic resins, it is preferable that the melting point of the polyolefin resin is 110° C. or less, and more preferably, in this case, the melting point of the polyolefin resin is 70° C. or more and less than 110° C. This makes it possible to particularly significantly exhibit the effect obtained by setting the surface roughness Ra of adhesive layer 11 on the surface facing resin substrate 21 to 0.20 μm or less, i.e., the effect that protective film 10, once peeled off, can be reattached to resin substrate 21 with excellent re-adhesion.

[0054] In this specification, the melting point of each layer constituting the protective film 10 including the adhesive layer 11 is defined as the value calculated by summing the melting points (peak temperatures measured by DSC) of the constituent materials contained in each layer that have a melting point, multiplied by the ratio of each constituent material contained therein.

[0055] In the adhesive layer 11 having such a configuration, as described above, the surface roughness Ra of the surface on the resin substrate 21 side measured in accordance with JIS B 0601 is set to 0.20 μm or less, preferably 0.16 μm or less, and more preferably 0.01 μm or more and 0.12 μm or less. This allows the once peeled protective film 10 to exhibit excellent re-adhesion to the resin substrate 21 when the peeled protective film 10 is re-attached to the resin substrate 21 (see FIG. 3(c)), as shown in FIG. 2(b).

[0056] The adhesive layer 11 preferably has an average thickness of 5 μm or more and 40 μm or less, and more preferably 10 μm or more and 20 μm or less, so that the adhesive layer 11 can reliably perform the above-mentioned function.

[0057] <<Base material layer 15>> The base material layer 15 is bonded to the resin substrate 21 (coating layer 24) via the adhesive layer 11, and functions as a protective layer (functional layer) to protect (mask) the resin substrate 21 when punching and heat-bending the resin substrate 21 in the steps [2] and [3], and to peel (detach) the resin substrate 21 (protective film 10) from the mold used for heat-bending after heat-bending in the step [3].

[0058] Furthermore, in the step [4], when the protective film 10 is peeled off from the thermally bent resin substrate 21, no peeling occurs between the base material layer 15 and the adhesive layer 11, and the protective film 10 exhibits excellent adhesion to the adhesive layer 11.

[0059] In order to allow the base material layer 15 to exhibit these functions, in the present invention, as shown in Figure 3, the base material layer 15 is composed of a laminate having a first layer 16 located on the side opposite the adhesive layer 11, i.e., the mold side, and a second layer 17 located on the adhesive layer 11 side, i.e., the resin substrate 21 side.

[0060] The first layer 16 and the second layer 17 will be described below. <<First Layer 16>> The first layer 16 is located on the opposite side of the adhesive layer 11 and functions as the outermost layer for protecting (masking) the resin substrate 21 when punching and heat bending the resin substrate 21 in the steps [2] and [3].

[0061] The melting point of the first layer 16 is preferably 150°C or higher, and more preferably about 155°C to 170°C, in order to maintain excellent releasability from the mold after the heat bending in step [3], i.e., to prevent the first layer 16 from adhering to the mold (metal mold). As described above, the heating temperature of the coating layer 24 (resin substrate 21) during the heat bending in step [3] is preferably set to about 110°C to 160°C. Therefore, by setting the melting point of the first layer 16 as described above, it is possible to reliably prevent the first layer 16 from melting or softening during the heat bending in step [3], and therefore the laminate 100 can be reliably released from the mold after the heat bending in step [3].

[0062] The first layer 16 preferably contains, as its main material, a thermoplastic resin having a melting point of 150°C or higher, more preferably a thermoplastic resin having a melting point of approximately 155°C or higher and 170°C or lower. This makes it relatively easy to set the melting point of the first layer 16 to 150°C or higher. This allows the laminate 100 to maintain excellent releasability from the mold after the heat bending in step [3].

[0063] Furthermore, when the second layer 17 described below also contains a thermoplastic resin having a temperature of 150° C. or higher, it is possible to achieve better adhesion between the first layer 16 and the second layer 17. Therefore, when the protective film 10 is peeled off from the thermally bent resin substrate 21 in the step [4], peeling between the first layer 16 and the second layer 17 can be appropriately suppressed or prevented.

[0064] Furthermore, the first layer 16 preferably has a configuration in which a polyolefin-based resin of 150°C or higher is contained solely as the thermoplastic resin of 150°C or higher in the first layer 16. The polyolefin-based resin of 150°C or higher is relatively easy to obtain and inexpensive as a thermoplastic resin of 150°C or higher.

[0065] The polyolefin resin having a melting point of 150°C or higher is not particularly limited, and examples thereof include polypropylene homopolymers, polyethylene homopolymers, propylene-ethylene copolymers, ethylene-vinyl acetate copolymers, ethylene-ethyl acrylate copolymers, and ethylene-methyl methacrylate copolymers, each having a melting point of 150°C or higher. One or more of these may be used in combination, and polypropylene homopolymers having a melting point of 150°C or higher are preferred. This allows polyolefin resins having a melting point of 150°C or higher to be easily and inexpensively obtained. Furthermore, transparency can be imparted to the first layer 16. Therefore, if the second layer 17 and the adhesive layer 11 are also transparent, the protective film 10 will also be transparent. Therefore, when the protective film 10 is attached to the resin substrate 21 in step [1], and when the protective film 10 is reattached to the resin substrate 21 prior to step [2], it is possible to visually determine whether or not dust or other debris is present between the protective film 10 and the resin substrate 21, and this makes it possible to reliably prevent the laminate 100 containing debris from being transferred after step [2], thereby improving the yield of the sunglass lenses 200 obtained.

[0066] The copolymer may be either a block copolymer or a random copolymer.

[0067] The first layer 16 preferably has an average thickness of 2 μm or more and 40 μm or less, and more preferably 5 μm or more and 25 μm or less, so that the first layer 16 can reliably perform its function as described above.

[0068] <<Second Layer 17>> The second layer 17 is located on the adhesive layer 11 side, i.e., on the resin substrate 21 side, and is therefore located between the adhesive layer 11 and the first layer 16, functioning as an intermediate layer that bonds them together.

[0069] In order to perform the above function, the second layer 17 contains, as a main material, a thermoplastic resin having adhesive (stickiness), which allows the adhesive layer 11 and the first layer 16 to be bonded with excellent adhesion via the second layer 17. Therefore, when the protective film 10 is peeled off from the resin substrate 21 in the step [4], peeling between the adhesive layer 11 and the second layer 17 and between the first layer 16 and the second layer 17 is appropriately suppressed or prevented. Therefore, even if whiskers, in which the adhesive layer 11 extends toward the resin substrate 21, are generated on the cut surface of the resin substrate 21 formed by punching when the resin substrate 21 is punched out in the step [2], the protective film 10 (adhesive layer 11) can be peeled off from the resin substrate 21 in a state in which the whiskers are appropriately suppressed or prevented from remaining on the cut surface of the resin substrate 21.

[0070] The adhesive thermoplastic resin (adhesive resin) is not particularly limited, but examples thereof include polyolefin resins, elastomers, acrylic resins, and polyurethane resins. One or more of these can be used in combination, but adhesive polyolefin resins and elastomers are preferred. Furthermore, when the adhesive layer 11 contains an elastomer, a combination of a polyolefin resin and an elastomer is particularly preferred. This improves adhesion between the adhesive layer 11 and the second layer 17, effectively suppressing or preventing peeling between the adhesive layer 11 and the second layer 17.

[0071] Examples of polyolefin resins include ethylene-vinyl acetate copolymer (EVA), ethylene-maleic anhydride copolymer, ethylene-methyl methacrylate copolymer (EMMA), ethylene-methyl acrylate copolymer (EMA), ethylene-methacrylic acid copolymer (EMAA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylic acid copolymer (EEA), and ethylene-methacrylate-glycidyl acrylate terpolymers. These include grafted products obtained by grafting various polyolefin resins with monobasic unsaturated fatty acids such as acrylic acid and methacrylic acid, dibasic unsaturated fatty acids such as maleic acid, fumaric acid, and itaconic acid, or anhydrides thereof, and functional group-introduced products obtained by grafting various polyolefin resins with functional groups such as carboxylic acid groups, hydroxyl groups, amino groups, acid anhydride groups, oxazoline groups, and epoxy groups. These can be used alone or in combination of two or more. Examples of the grafted product include maleic acid grafted EVA and maleic acid grafted ethylene-α-polyolefin resin copolymer.

[0072] Furthermore, the elastomer may be the same as that described for the elastomer contained in adhesive layer 11, and among these, a styrene block elastomer is preferable, and a styrene-olefin-styrene block copolymer elastomer is particularly preferable. By using an elastomer containing styrene as a monomer component, the adhesion of second layer 17 to adhesive layer 11 is improved, and therefore, in the step [4], the occurrence of adhesive residue on resin substrate 21 can be more reliably suppressed or prevented.

[0073] Furthermore, the second layer 17 may contain, as its constituent material, a non-adhesive thermoplastic resin (non-adhesive resin) in addition to the adhesive thermoplastic resin. The non-adhesive thermoplastic resin exhibits excellent affinity with the polyolefin resin with a melting point of 150°C or higher contained in the first layer 16, and therefore can improve the adhesion between the first layer 16 and the second layer 17. Therefore, when the protective film 10 is peeled off from the resin substrate 21 in the step [4], peeling between the first layer 16 and the second layer 17 can be appropriately suppressed or prevented.

[0074] Examples of non-adhesive thermoplastic resins include polyolefin resins, polyesters, polyurethanes, silicone resins, polyamides, polyimides, polyvinyl chloride, polycarbonates, etc., and these can be used alone or in combination of two or more, but among these, polyolefin resins are preferred, and polyolefin resins with a melting point of 150° C. or higher are more preferred, which allows the above-mentioned effects to be more pronounced.

[0075] The polyolefin resin is not particularly limited and may be, for example, a polypropylene homopolymer, a polyethylene homopolymer, a propylene-ethylene copolymer, an ethylene-vinyl acetate copolymer, an ethylene-ethyl acrylate copolymer, or an ethylene-methyl methacrylate copolymer. One or more of these may be used in combination, and a polypropylene homopolymer is particularly preferred. This allows the polyolefin resin to be easily and inexpensively obtained. Furthermore, transparency can be imparted to the second layer 17. Therefore, if the first layer 16 and the adhesive layer 11 are also transparent, the protective film 10 will also be transparent. Therefore, when the protective film 10 is attached to the resin substrate 21 in step [1], and when the protective film 10 is reattached to the resin substrate 21 prior to step [2], it is possible to visually determine whether or not dust or other debris is present between the protective film 10 and the resin substrate 21, and this makes it possible to reliably prevent the laminate 100 containing debris from being transferred after step [2], thereby improving the yield of the sunglass lenses 200 obtained.

[0076] Furthermore, the melting point of the polyolefin resin having a melting point of 150°C or higher is preferably 155°C or higher and 170°C or lower.

[0077] The copolymer may be either a block copolymer or a random copolymer. However, polyolefin resins with a melting point of 150°C or higher are generally used as non-adhesive thermoplastic resins because they do not have adhesive properties by themselves, but for example, propylene-ethylene random copolymers (melting point: 151°C) have adhesive properties and are therefore used as adhesive thermoplastic resins.

[0078] For these reasons, when second layer 17 contains a non-adhesive thermoplastic resin, a preferred combination of adhesive thermoplastic resin and non-adhesive thermoplastic resin is an elastomer and a polyolefin resin with a melting point of 150° C. or higher. By using such a combination, peeling between adhesive layer 11 and second layer 17, and between first layer 16 and second layer 17, can be reliably suppressed or prevented.

[0079] The second layer 17 having the above-described configuration preferably has a melting point of 120°C or higher. Here, as described above, the heating temperature of the coating layer 24 (resin substrate 21) during the heat bending in step [3] is preferably set to approximately 110°C or higher and 160°C or lower. Therefore, when the melting point of the second layer 17 is set to 120°C or higher and lower than 150°C, the second layer 17 can be relatively easily melted or softened during the heat bending in step [3]. Therefore, in step [3], the second layer 17 functions as an intermediate layer in a melted or softened state, allowing the first layer 16 to be displaced relative to the surface direction of the resin substrate 21, thereby forming a gripping space for the first layer 16 at the edge of the laminate 100. Therefore, peeling of the protective film 10 in step [4] can be performed by gripping the gripping space, making this peeling easy. Furthermore, in the step [3], the second layer 17 is allowed to function as an intermediate layer in a molten or softened state, thereby improving the cushioning properties of the second layer 17 during molding using a mold. As a result, irregularities of the mold or irregularities of contaminants that have unintentionally become mixed in between the mold and the protective film 10 can be effectively absorbed, and the thermally bent resin substrate 21 can be obtained as one with an excellent appearance.

[0080] Furthermore, when the melting point of the second layer 17 is set to 150°C or higher, it is possible to suppress or prevent the second layer 17 from melting or softening during the thermal bending in the step [3]. This effectively suppresses or prevents a decrease in the adhesive strength between the first layer 16 and the second layer 17. Therefore, when the protective film 10 is peeled off from the thermally bent resin substrate 21 in the step [4], peeling between the first layer 16 and the second layer 17 is reliably prevented.

[0081] The average thickness of the second layer 17 is preferably 10 μm or more and 60 μm or less, and more preferably 10 μm or more and 40 μm or less, so that the second layer 17 can reliably perform the above-mentioned function.

[0082] The protective film 10 having the adhesive layer 11 and the base layer 15 configured as described above preferably has a modulus of elasticity at 25°C of 300 MPa to 600 MPa, more preferably 300 MPa to 500 MPa, even more preferably 300 MPa to 450 MPa, and particularly preferably 300 MPa to 400 MPa. This allows the adhesive layer 11 to be said to have excellent flexibility in low temperature regions such as room temperature, and therefore the effect obtained by setting the surface roughness Ra of the adhesive layer 11 on the surface facing the resin substrate 21 to 0.2 μm or less, i.e., the effect that the protective film 10, once peeled off, can be reattached to the resin substrate 21 with excellent re-adhesion, can be more significantly exhibited.

[0083] Specifically, the re-adhesion of this protective film 10 was evaluated by applying a protective film 10 measuring 25 mm in width and 200 mm in length to a polycarbonate substrate, and then, in an environment of 25°C, holding one end of the protective film 10 and peeling it off at a 90° angle to a position 100 mm in length. After releasing the one end of the protective film 10, the protective film 10 was re-applied to the polycarbonate substrate. One minute after re-application, the total area in a plan view of the area where the polycarbonate substrate and the protective film were not bonded was 1,250 mm 2 Preferably less than 750 mm 2 Preferably less than 125 mm 2 It is even more preferable that the total area is less than this upper limit. By setting the total area to be equal to or less than the upper limit, the protective film 10 can be said to have excellent re-adhesion properties, and the protective film 10 that has been peeled off once can be reliably attached to the resin substrate 21 again. This makes it possible to appropriately suppress or prevent the protective film 10, and in turn the resin substrate 21, from being wasted. Therefore, the sunglass lenses 200 can be manufactured with a good yield.

[0084] In addition, the number of regions where the polycarbonate substrate and the protective film are not bonded is preferably 20 or less, more preferably 10 or less, and even more preferably 3 or less. By setting the number to the upper limit or less, the protective film 10 can be said to have better re-adhesion properties.

[0085] In addition to the above-mentioned constituent materials, each of the adhesive layer 11 and base layer 15 (first layer 16 and second layer 17) of the protective film 10 may contain various additives such as an antiblocking agent, an antioxidant, a light stabilizer, an antistatic agent, etc. The content of the additives may be 10% by weight or less, 8% by weight or less, 0.001% by weight or more, or 0.1% by weight or more.

[0086] In particular, it is preferable that the first layer 16 contains an antiblocking agent, which allows the first layer 16 to more reliably exhibit its function of maintaining excellent releasability from the molding die.

[0087] The antiblocking agent may be, for example, inorganic particles or organic particles, and one or more of these may be used in combination. The inorganic particles are not particularly limited, but examples thereof include particles of silica, zeolite, smectite, mica, vermiculite, and talc, while the organic particles are not particularly limited, but examples thereof include particles of acrylic resins, polyolefin resins, polyester resins, polyurethane resins, polystyrene resins, silicone resins, and fluorine resins.

[0088] When the first layer 16 contains an antiblocking agent, the content of the antiblocking agent in the first layer 16 is not particularly limited, but is preferably set to 0.5% by weight or more and 10% by weight or less, and more preferably 1% by weight or more and 9% by weight or less, which allows the first layer 16 to more significantly exhibit the above-mentioned functions.

[0089] Between these layers, an intermediate layer containing the above-mentioned additives may be formed. Furthermore, the above-described protective film 10 may be produced by any method, but may be produced, for example, by using a co-extrusion method.

[0090] Specifically, three extruders are prepared, and the constituent materials of the adhesive layer 11, the first layer 16, and the second layer 17 are respectively placed in these extruders. These are then extruded in a molten or softened state, and the molten or softened laminate, in which these layers are stacked in layers, is supplied from a co-extrusion T-die to a sheet forming section consisting of multiple cooling rolls, etc., and the laminate is then cooled in this sheet supply section to produce the protective film 10.

[0091] The surface roughness Ra of the adhesive layer on the side opposite the second layer can be adjusted to the desired size, for example, by using a cooling roll with a different surface roughness (e.g., a metal mirror roll) in the sheet forming unit, or by configuring the sheet forming unit to have an air chamber or air knife and blow air onto the surface of the adhesive layer.

[0092] The above describes the protective film of the present invention, but the present invention is not limited to this, and each layer constituting the protective film can be replaced with any other layer that can perform the same function.

[0093] In addition, in the above embodiment, in Figure 2, a case has been described in which the protective film is reattached to the resin substrate after a portion of the protective film has been peeled off from the resin substrate, but this is not limited to this, and the protective film can also be reattached after the entire protective film has been peeled off from the resin substrate.

[0094] Furthermore, in the above embodiment, the protective film of the present invention is described as being attached to a resin substrate when the resin substrate of a sunglass lens is subjected to a thermal bending process. However, the protective film of the present invention can be applied to the thermal bending of such resin substrates of sunglass lenses, and can also be used when thermally bending resin substrates such as lenses in goggles and visors in helmets. [Example]

[0095] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to these examples in any way.

[0096] 1. Raw material preparation First, the raw materials used in producing the protective films of the examples and comparative examples are as follows.

[0097] <<Non-adhesive thermoplastic resin>> <Polyolefin resin with a melting point of 150°C or higher> Homopolypropylene with a melting point of 167°C (h-PP, manufactured by Japan Polypropylene Corporation, "Novatec EA9FTD", MFR = 0.4g / 10min)

[0098] <Polyolefin resin with a melting point of 120°C or higher and lower than 150°C> Linear low-density polyethylene (LLDPE, manufactured by Ube Maruzen Polyethylene Co., Ltd., "Yumerit 2525F", MFR = 2.5 g / 10 min) with a melting point of 121°C

[0099] <Polyolefin resin with a melting point of less than 120°C> Linear low-density polyethylene (LLDPE, manufactured by Ube Maruzen Polyethylene Co., Ltd., "Yumerit 1520F", MFR = 2.0 g / 10 min) with a melting point of 114°C

[0100] <Polyolefin resin with a melting point of less than 110°C> Linear low-density polyethylene (LLDPE, manufactured by Tosoh Corporation, "Niboron-Z HF212R", MFR = 2.0 g / 10 min) with a melting point of 93°C

[0101] <<Thermoplastic resin with adhesive properties>> <Elastomer> Styrene-ethylene-butylene-styrene block copolymer (SEBS, manufactured by Asahi Kasei Corporation, "Tuftec H1221") Hydrogenated styrene-butadiene random copolymer (HSBR, manufactured by JSR Corporation, "Dynaron 1320P")

[0102] <Polyolefin resin> Ethylene-methyl acrylate copolymer with a melting point of 90°C (EMA, manufactured by Japan Polyethylene Corporation, "Rexpearl EB330H") Block polypropylene (b-PP) with a melting point of 165°C (Sumitomo Chemical Co., Ltd., "Noblen KS23F8", MFR = 2.1 g / 10 min)

[0103] <Polyolefin resin with a melting point of 120°C or higher and lower than 150°C> Random polypropylene copolymer with a melting point of 131°C (r-PP, manufactured by Sumitomo Chemical Co., Ltd., "Noblen S131", MFR = 1.3 g / 10 min)

[0104] <<Anti-blocking agent>> Anti-blocking agent (Kinoplus FPP-AB05A, manufactured by Sumika Color Co., Ltd.)

[0105] 2.Protective film manufacturing Example 1 [1] First, to form the adhesive layer (innermost layer), LLDPE with a melting point of 121°C as a polyolefin resin and SEBS as an elastomer were mixed so that the SEBS content was 10% by weight to prepare an adhesive layer-forming material (resin composition).

[0106] [2] Next, to form the second layer (intermediate layer) of the base material layer, SEBS was used as an adhesive thermoplastic resin, and h-PP with a melting point of 167°C was used as a non-adhesive thermoplastic resin. The SEBS content was 20% by weight, and thus a second layer-forming material (resin composition) was prepared.

[0107] [3] Next, the prepared adhesive layer-forming material, the prepared second layer-forming material, and h-PP with a melting point of 167°C as a polyolefin resin with a melting point of 150°C or higher to form the first layer (outermost layer) were placed in three extruders, respectively.

[0108] [4] Next, the molten mixture was extruded from the three extruders, and a molten laminate in which the mixture was layered was obtained from a co-extrusion T-die.A metal mirror roll was then pressed against the adhesive layer to form a mirror-finished adhesive layer on the surface thereof.Then, the laminate was cooled to obtain the protective film of Example 1, in which the average thicknesses of the first layer, second layer, and adhesive layer were 10 μm, 30 μm, and 10 μm, respectively.

[0109] The surface roughness Ra of the adhesive layer on the side opposite to the second layer was measured in accordance with JIS B 0601 using a laser microscope (Keyence Corporation, "VK9700") and was found to be 0.05 μm.

[0110] Furthermore, in accordance with JIS K 7127 for protective films, a test piece (No. 1 dumbbell) taken from the film was measured in an atmosphere of 23°C and 60% RH using a Shimadzu autograph (tensile speed: 500 mm / min), and the result was 475 MPa.

[0111] (Examples 2 and 3) The protective films of Examples 2 and 3 were obtained in the same manner as in Example 1, except that in step [4], the adhesive layer was formed by blowing air onto the surface of the adhesive layer using an air chamber or an air knife.

[0112] (Comparative Example 1) The protective film of Comparative Example 1 was obtained in the same manner as in Example 1, except that in step [4], the adhesive layer was formed by pressing a metal roll without a mirror surface against the adhesive layer.

[0113] (Comparative Example 2, Comparative Example 3) Protective films of Comparative Examples 2 and 3 were obtained in the same manner as Comparative Example 1, except that the type of polyolefin resin used in the step [1] was changed as shown in Table 1.

[0114] Example 4 The protective film of Example 4 was obtained in the same manner as in Example 1, except that the type of polyolefin resin and the type of elastomer used in step [1] were changed as shown in Table 1.

[0115] (Examples 5 and 6) The protective films of Examples 5 to 6 were obtained in the same manner as in Example 4, except that in step [4], the adhesive layer was formed by blowing air onto the surface of the adhesive layer using an air chamber or an air knife.

[0116] Example 7 A protective film of Example 7 was obtained in the same manner as in Example 1, except that the type of polyolefin resin used in the step [1] was changed as shown in Table 1.

[0117] (Examples 8 to 9) The protective films of Examples 8 to 9 were obtained in the same manner as in Example 7, except that in step [4], the adhesive layer was formed by blowing air onto the surface of the adhesive layer using an air chamber or an air knife.

[0118] Example 10 A protective film of Example 10 was obtained in the same manner as in Example 1, except that the type of polyolefin resin used in the step [1] was changed as shown in Table 1.

[0119] (Examples 11 and 12) The protective films of Examples 11 and 12 were obtained in the same manner as in Example 10, except that in step [4], the adhesive layer was formed by blowing air onto the surface of the adhesive layer using an air chamber or an air knife.

[0120] Example 13 [1] First, to form the adhesive layer (innermost layer), LLDPE with a melting point of 93°C was prepared as a polyolefin resin for forming the adhesive layer.

[0121] [2] Next, to form the second layer (intermediate layer) of the base layer, b-PP with a melting point of 158°C was prepared as a thermoplastic resin having adhesive properties.

[0122] [3] Next, the adhesive layer forming material, the second layer forming material, and h-PP with a melting point of 167°C as a polyolefin resin with a melting point of 150°C or higher to form the first layer (outermost layer) were placed in three extruders, respectively.

[0123] [4] Next, these were extruded in a molten state from three extruders to obtain a molten laminate in which these were layered from a co-extrusion T-die, and then a metal mirror roll was pressed against the adhesive layer to form a mirror-finished adhesive layer on the surface of the adhesive layer, and then this laminate was cooled to obtain the protective film of Example 13, in which the average thicknesses of the first layer, second layer, and adhesive layer were 10 μm, 30 μm, and 10 μm, respectively. The surface roughness Ra of the adhesive layer on the side opposite the second layer was measured and found to be 0.06 μm.

[0124] Example 14 The protective film of Example 14 was obtained in the same manner as in Example 13, except that in the step [4], the adhesive layer was formed by blowing air onto the surface of the adhesive layer using an air knife. The surface roughness Ra of the adhesive layer on the side opposite to the second layer was measured and found to be 0.16 μm.

[0125] Example 15 The protective film of Example 15 was obtained in the same manner as in Example 13, except that in step [3], a polyolefin resin having a melting point of 150°C or higher was used as the first layer (outermost layer) forming material, and an antiblocking agent (Kinoplus FPP-AB05A) was prepared as shown in Table 1.

[0126] 3. Evaluation The protective films of the examples and comparative examples were evaluated by the following methods. <1> Re-adhesion of the protective film to the substrate First, a protective film measuring 25 mm wide x 200 mm long for each of the examples and comparative examples was sandwiched between two polycarbonate substrates (manufactured by Sumitomo Bakelite Co., Ltd., "ECK100UU") measuring 30 cm long x 30 cm wide x 2.0 mm thick, with the mirror surface facing the protective film side, and a load of 1 kg / cm was applied. 2 The protective film was attached to the polycarbonate substrate located on the adhesive layer side by pressing with a roll under the conditions of

[0127] The polycarbonate that constitutes the polycarbonate substrate is an aromatic polycarbonate resin obtained by the interfacial polycondensation reaction of bisphenol A and phosgene, and after being sheeted by extrusion molding, a mirror finish is given to the substrate by mold transfer.

[0128] Next, the protective film was sandwiched between the polycarbonate substrates and held at 25°C for 30 minutes. Then, in an environment of 25°C, one end of the protective film was held and peeled off from the polycarbonate substrate at a 90° angle to a length of 100 mm. The protective film was then reattached to the polycarbonate substrate by releasing the end of the protective film.

[0129] One minute after the re-attachment, the total area (mm ) of the area where the polycarbonate substrate and the protective film were not bonded in a plan view was 2 ) was measured, and the number of regions where the polycarbonate substrate and the protective film were not bonded was counted, and the obtained total area and number were evaluated based on the following evaluation criteria.

[0130] (Total area evaluation) The total area of ​​the area where the polycarbonate substrate and the protective film are not bonded is ◎◎:125mm 2 is less than ◎ :125mm 2 More than 750mm 2 is less than 〇: 750mm 2 More than 1,250mm 2is less than × :1,250mm 2 That's all

[0131] (Quantity evaluation) The number of areas where the polycarbonate substrate and the protective film are not bonded is ◎◎: 3 or less ◎: More than 3 and up to 10 〇: More than 10 and less than 20 ×: More than 20

[0132] <2> Evaluating whether whisker adhesion exists on resin substrates First, for the protective films of each of the examples and comparative examples, a load of 0.5 kg / cm was applied to both sides of a resin substrate (manufactured by Sumitomo Bakelite Co., Ltd.) having a structure in which a polarizer was sandwiched between two polycarbonate substrates (polycarbonate layers). 2 A protective film was attached by pressing using a roll under the conditions of (a) to (c) to obtain a laminate.

[0133] Next, after storing the laminate at a temperature of 23°C for 12 hours, the laminate, i.e., the resin substrate with protective films attached to both sides, was punched out in the thickness direction to give the laminate a circular shape when viewed from above.

[0134] Next, the two protective films were peeled off from the laminate, and the punched surface (cut surface) of the resin substrate 21 was visually inspected for the presence or absence of remaining whiskers (adhesive layer). If no remaining whiskers were found, they were evaluated as ◎; if some remaining whiskers were found, they were evaluated as ○; if remaining whiskers were clearly found, they were evaluated as ×.

[0135] <3> Evaluating whether orange peel formation occurs on the surface of a resin substrate First, for the protective films of each of the examples and comparative examples, a load of 0.5 kg / cm was applied to both sides of a resin substrate (manufactured by Sumitomo Bakelite Co., Ltd.) having a structure in which a polarizer was sandwiched between two polycarbonate substrates (polycarbonate layers). 2A protective film was attached by pressing using a roll under the conditions of (a) to (c) to obtain a laminate.

[0136] Next, after storing the laminate at a temperature of 23°C for 12 hours, the laminate, i.e., the resin substrate with protective films attached to both sides, was punched out in the thickness direction to give the laminate a circular shape when viewed from above.

[0137] Next, the circular laminate was subjected to a hot bending process under heating using a Rema molding machine (manufactured by Rema Co., Ltd., "CR-32 type") equipped with a mold.

[0138] Next, the two protective films were peeled off from the laminate, and the attached surface (peeling surface) of the resin substrate 21 was visually observed for the presence or absence of orange peel (unevenness). If no orange peel was observed, it was evaluated as ◯, and if orange peel was observed, it was evaluated as ×.

[0139] The evaluation results for the protective films of the Examples and Comparative Examples obtained as described above are shown in Table 1 below.

[0140] [Table 1]

[0141] As shown in Table 1, in the protective film of each example, the surface roughness Ra of the surface of the adhesive layer is set to 0.20 μm or less, so that the total area in plan view of the region where the polycarbonate substrate and the protective film are not bonded is 1250 mm 2 It was found that the protective film was able to exhibit re-adhesion to the resin substrate, and satisfied the requirement that the number of areas where the polycarbonate substrate and the protective film were not bonded was 20 or less.

[0142] In contrast, in the protective films of each comparative example, the surface roughness Ra of the adhesive layer surface was not set to 0.20 μm or less, and as a result, the total area in plan view of the region where the polycarbonate substrate and the protective film were not bonded was 1250 mm 2 The number of regions where the polycarbonate substrate and the protective film are not bonded was less than 20, and the number of regions where the polycarbonate substrate and the protective film are not bonded was not 20 or less. In other words, the protective film was not able to exhibit re-adhesion to the resin substrate. [Explanation of symbols]

[0143] 10 Protective film 11 Adhesive layer 15 Base material layer 16 First Layer 17 Second Layer 21 Resin substrate 23 Polarizer 24 Covering layer 30 polycarbonate layers 100 laminate 200 Sunglasses Lenses

Claims

1. A protective film to be attached to a resin substrate when the resin substrate is subjected to a thermal bending process under heating, a substrate layer; an adhesive layer positioned between the base layer and the resin substrate and adhering to the resin substrate; the base material layer is composed of a laminate having a first layer located on the opposite side of the adhesive layer and a second layer located on the adhesive layer side, the adhesive layer has a surface roughness Ra of 0.20 μm or less on the surface facing the resin substrate, as measured in accordance with JIS B 0601; A protective film characterized in that the modulus of elasticity is 300 MPa or more and 600 MPa or less when a test piece (No. 1 dumbbell) taken from the protective film is measured in accordance with JIS K 7127 under an atmosphere of 23°C and 60% RH using an autograph manufactured by Shimadzu Corporation at a tension rate of 500 mm / min.

2. The protective film according to claim 1, wherein the first layer contains a thermoplastic resin as its main material and has a melting point of 150°C or higher, the second layer contains a thermoplastic resin as its main material and has a melting point of 120°C or higher, and the adhesive layer contains a thermoplastic resin as its main material and has a melting point of 110°C or lower.

3. The protective film according to claim 2 , wherein the thermoplastic resin contained in the first layer and the thermoplastic resin contained in the second layer both contain polyolefin-based resins.

4. The protective film according to claim 1 , wherein the adhesive layer contains, as a main material, a polyolefin resin having adhesive properties.

5. The protective film having a width of 25 mm and a length of 200 mm was attached to a polycarbonate substrate, and then, in an environment of 25°C, one end of the protective film was held and peeled off in a 90° direction to a position of 100 mm in length. Then, the one end of the protective film was released and the protective film was reattached to the polycarbonate substrate. One minute after reattachment, the total area in a plan view of the region where the polycarbonate substrate and the protective film were not bonded was 1250 mm ２ The protective film according to claim 1 , wherein the thickness is less than 1 / 2 mm.

6. The protective film according to claim 1 , which is attached to both sides of the resin substrate.

7. The protective film according to any one of claims 1 to 6, wherein the resin substrate has a coating layer on both sides, one side or the other side, which is composed of a single layer or a laminate having at least one layer selected from the group consisting of a polycarbonate resin layer, a polyamide resin layer and a cellulose resin layer.

8. The protective film according to claim 1 , wherein the resin substrate is subjected to the heat bending process by press molding or vacuum molding.

Images