JP2022158894A - Protective film - Google Patents

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 The present invention relates to a protective film used by being attached to a resin substrate when subjecting the resin substrate to thermal bending under heating.

A lens for sunglasses comprising a resin substrate in which both sides of a polarizer are coated with a coating layer made of polycarbonate resin, polyamide resin or cellulose resin is, for example, protected on both sides of the resin substrate which is flat in plan view. With the film attached, the resin substrate is punched into a predetermined shape such as a circular shape in plan view, and then the resin substrate is subjected to thermal bending under heating. After peeling off the protective film from the heat-bent resin substrate, the polycarbonate layer is injection-molded on the concave surface of the resin substrate.

As this protective film, for example, a base material whose main material is polyolefin resin is attached to the resin substrate via an adhesive layer whose main material is polyethylene, ethylene-propylene copolymer, or the like. has been proposed (see, for example, Patent Document 1).

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 carried out by hand or by using an arm of a machine tool. In attaching such a protective film, at least a part of the protective film is once peeled off from the resin substrate due to wrinkles in the protective film or air bubbles remaining between the protective film and the resin substrate. Later, the peeled protective film may be re-attached to the resin substrate (reattached) to the resin substrate.

However, with the protective film configured as described above, it is not possible to obtain sufficient re-adherence of the protective film that is re-attached to the resin substrate after the protective film has been peeled off from the resin substrate. The actual situation is that the development of a protective film having excellent re-adhesion is required.

Such problems occur not only in the sunglasses lenses described above, but also in resin substrates such as the lenses of goggles and the visors of helmets.

JP-A-2003-145616

SUMMARY OF THE INVENTION An object of the present invention is to provide a protective film excellent in re-adhesion, which is adhered to a resin substrate, then peeled at least partially, and then adhered again to the resin substrate.

Such objects are achieved by the present invention described in (1) to (9) below.
(1) A protective film that is used by being attached to a resin substrate when the resin substrate is subjected to thermal bending under heating,
a substrate layer;
an adhesive layer positioned between the base material 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 protective film, wherein the adhesive layer has a surface roughness Ra of 0.20 μm or less on the surface on the resin substrate side, measured according to JIS B 0601.

(2) The protective film according to (1) above, which has an elastic modulus of 300 MPa or less and 600 MPa or less at 25°C.

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

(4) The protective film according to (3) above, wherein the thermoplastic resin contained in the first layer and the thermoplastic resin contained in the second layer both contain a polyolefin resin.

(5) The protective film according to any one of (1) to (4) above, wherein the adhesive layer contains an adhesive polyolefin resin as a main material.

(6) Affix the protective film of width 25 mm × length 200 mm on a polycarbonate substrate, then hold one end of the protective film in an environment of 25 ° C. and move it to the position of length 100 in the direction of 90 °. After peeling off, when the protective film is attached again to the polycarbonate substrate by separating the one end of the protective film, the polycarbonate substrate and the protective film are bonded 1 minute after the re-attachment. The protective film according to any one of (1) to (5) above, wherein the total area of the non-removed regions in plan view is less than 1250 mm ² .

(7) The protective film according to any one of (1) to (6), which is attached to both sides of the resin substrate.

(8) The resin substrate has a coating layer composed of a single layer or laminate having at least one layer selected from a polycarbonate resin layer, a polyamide resin layer and a cellulose resin layer on both sides, one side or the other side. The protective film according to any one of (1) to (7) above.

(9) The protective film according to any one of (1) to (8) above, wherein the resin substrate is subjected to the thermal bending process by press molding or vacuum molding.

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 on the resin substrate side, which is measured according to JIS B 0601. Thus, by setting the surface roughness Ra of the surface of the adhesive layer on the resin substrate side to the upper limit value or less, the protective film is attached to the resin substrate, and then at least partly peeled off. , it can be excellent in re-adhesion when re-adhered to the resin substrate.

It is a schematic diagram for demonstrating the manufacturing method of the lens for sunglasses using a protective film. FIG. 4 is a schematic diagram for explaining a method of peeling off at least a part of the protective film stuck on the resin substrate and then sticking it on the resin substrate again. 1 is a vertical cross-sectional view showing a preferred embodiment of a protective film of the present invention; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION The protective film of the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings. In this specification, the main material refers to a constituent material contained in each layer in an amount of 50% by weight or more. For example, "the first layer 16 contains thermoplastic resin as its main material "The thermoplastic resin contained in the first layer 16 accounts for 50% by weight or more in the first layer 16 when the total weight of the first layer 16 is 100% by weight. point to

The protective film of the present invention is a protective film that is used by being attached to the resin substrate when the resin substrate is subjected to thermal bending under heating. and an adhesive layer positioned between and adhering to the resin substrate, wherein the base material layer includes a first layer positioned on the opposite side of the adhesive layer and a second layer positioned 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, which is measured in accordance with JIS B 0601. and

By making the protective film have such a configuration, that is, by setting the surface roughness Ra of the surface of the adhesive layer provided in the protective film on the resin substrate side to the upper limit value or less, the protective film can be attached to the resin substrate. Then, after peeling off at least a part of the adhesive layer, it can be attached again to the resin substrate, thereby providing excellent re-adhesion.

Before describing the protective film of the present invention, a method for manufacturing a lens for sunglasses using the protective film of the present invention will be described below.

<Manufacturing method of lens for sunglasses>
FIG. 1 is a schematic diagram for explaining a method of manufacturing a sunglass lens using a protective film, and FIG. FIG. 3 is a schematic diagram for explaining a method of sticking by pressing. For convenience of explanation, the upper side of FIGS. 1 and 2 is hereinafter referred to as "upper", and the lower side thereof is referred to as "lower".

Each step of the method for manufacturing a lens for sunglasses will be described in detail below.
[1] First, a resin substrate 21 having a flat plate shape is prepared, and protective films 10 (masking tape) are attached to both surfaces of the resin substrate 21, so that the protective films 10 are attached to both surfaces of the resin substrate 21. A laminate 100 is obtained (see FIG. 1(a)).

In this embodiment, the resin substrate 21 is a polarizer 23 that functions as an optical element that extracts linearly polarized light having a plane of polarization in one predetermined direction from unpolarized natural light. will be prepared. In this resin substrate 21, the coating layer 24 is composed of a single layer or 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. Furthermore, the coating layer 24 may be formed on both surfaces (both surfaces) of the polarizer 23, or may be formed on either the upper surface (one surface) or the lower surface (the other surface). may

[2] Next, as shown in FIG. 1B, the prepared laminate 100, that is, the resin substrate 21 with the protective films 10 attached to both surfaces thereof, is punched out in the thickness direction. Thus, the laminated body 100 has a circular shape in plan view.

[3] Next, as shown in FIG. 1(c), the circular laminated body 100 is subjected to thermal bending under heating.

This thermal bending is usually performed by press molding using a mold or vacuum molding (rema molding).

At this time, the heating temperature (molding temperature) of the laminate 100 (resin substrate 21) is as described above. and at least one of the cellulose resin layers, the melting or softening temperature of the coating layer 24 is taken into account, and the temperature is preferably about 110° C. or higher and 160° C. or lower. , more preferably about 140° C. or higher and 150° C. or lower. By setting the heating temperature within such a range, the resin substrate 21 can be reliably thermally bent by softening or melting the resin substrate 21 while preventing alteration and deterioration of the resin substrate 21 .

[4] Next, as shown in FIG. 1(d), after peeling off the protective film 10 from the heat-bent resin substrate 21, that is, the laminate 100, the concave surface of the resin substrate 21 is made of polycarbonate resin. Injection molded polycarbonate layer 30 . A polyamide layer composed of a polyamide resin may be formed on the concave surface of the resin substrate 21 instead of the polycarbonate layer 30 .

As a result, the sunglasses lens 200 including the thermally bent resin substrate 21 is manufactured.

Here, in the above-described method for manufacturing a lens for sunglasses, protective films are formed on both sides of the resin substrate 21 in the step [1] prior to the punching in the thickness direction of the resin substrate 21 in the step [2]. 10 is attached, thereby obtaining a laminate 100 in which the protective films 10 are attached to both surfaces of the resin substrate 21 .

Attachment of the protective film 10 to the laminate 100 is usually carried out using a human hand, an arm provided with a machine tool, or the like. Air bubbles may remain between the resin substrate 21 and the resin substrate 21 .

In this case, one end of the protective film 10 in the laminate 100 in which the protective films 10 are attached to both sides of the resin substrate 21 as shown in FIG. , and part of the protective film 10 is once peeled off by peeling off the protective film 10 halfway from this one end. Then, the gripping of one end of the protective film 10 is released, and the peeled protective film 10 is again attached to the resin substrate 21, so that the protective film 10 is attached to the resin substrate 21 as shown in FIG. ), it is re-applied (re-adhered). However, when the protective film 10 is re-applied to the resin substrate 21 in this manner, the adhesion of the protective film 10 to the resin substrate 21 is sufficiently improved compared to when the protective film 10 is adhered to the resin substrate 21 for the first time. There was a problem that it was not possible to obtain

As a result of investigations by the present inventors regarding such problems, the re-adhesion of the once-peeled protective film 10 to the resin substrate 21 was found to , is closely related to the surface properties of the surface of the adhesive layer 11 on the resin substrate 21 side.

Further, the present inventors further examined the relationship between the re-adherence of the protective film 10 and the surface properties of the surface of the adhesive layer 11 on the resin substrate 21 side. By setting the surface roughness Ra on the surface to 0.20 μm or less, the protective film 10 once peeled exhibits excellent re-adhesion to the resin substrate 21. To complete the present invention, Arrived.

Therefore, by using the protective film of the present invention in which the surface roughness Ra on the surface of the resin substrate 21 side is set to 0.20 μm or less as the protective film 10 and re-adhering the protective film 10, the protective film Waste of the resin substrate 21 can be appropriately suppressed or prevented. Therefore, the sunglasses lens 200 can be manufactured with a high yield. The protective film 10 (protective film of the present invention) will be described in detail below.

<Protective film 10>
FIG. 3 is a longitudinal sectional view showing a preferred embodiment of the protective film of the invention. For convenience of explanation, the upper side of FIG. 3 is hereinafter referred to as "upper", and the lower side thereof is referred to as "lower".

The protective film 10 has a substrate layer 15 and an adhesive layer 11 positioned between the substrate layer 15 and the resin substrate 21 to adhere (bond) to the resin substrate 21, as shown in FIG. The base material layer 15 comprises a first layer 16 located on the opposite side of 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. have.

Each of these layers will be described in detail below.
<<adhesive layer 11>>
The adhesive layer 11 is positioned (interposed) between the base material layer 15 and the resin substrate 21 and adheres to the resin substrate 21 to bond the base material layer 15 to the resin substrate 21 .

This adhesive layer 11 allows punching and thermal bending of the resin substrate 21 in the steps [2] and [3] without peeling the protective film 10 from the resin substrate 21, and also allows ] is preferably used to peel the protective film 10 from the resin substrate 21 .

Furthermore, in the present invention, in re-adhering the protective film 10 to the resin substrate 21, which is performed as necessary prior to the step [2], excellent re-adhesion is achieved. What can be demonstrated is used.

From this point of view, the adhesive layer 11 preferably contains an adhesive thermoplastic resin as a main material, and more preferably contains a thermoplastic resin having a melting point of 110° C. or lower. By using the adhesive layer 11 having such a configuration, the effect obtained by setting the surface roughness Ra of the surface of the adhesive layer 11 on the resin substrate 21 side to 0.20 μm or less, that is, once peeled The effect that the protective film 10 can be re-attached to the resin substrate 21 with excellent re-adhesion can be remarkably exhibited. In addition, since the adhesive layer 11 contains a thermoplastic resin having a melting point of 110° C. or lower, the melting point of the adhesive layer 11 can be easily set to 110° C. or lower. As a result, the adhesive layer 11 can be provided with excellent flexibility in a low temperature range such as normal temperature, so that the effect obtained by setting the surface roughness Ra to 0.20 μm or less is more remarkable. can be exhibited. That is, the protective film 10 that has once been peeled off can be re-attached to the resin substrate 21 with better re-adhesion. From the viewpoint of exhibiting such effects more remarkably, the melting point of the adhesive layer 11 is preferably 110° C. or lower, more preferably 100° C. or lower, and more preferably 70° C. or higher and 95° C. or lower. It is even more preferable to have

In addition, the adhesive layer 11 has a configuration in which a polyolefin-based resin alone is contained in the adhesive layer 11 as a thermoplastic resin, or a configuration in which a polyolefin-based resin and an elastomer are combined in the adhesive layer 11. is preferred. By making the adhesive layer 11 have a structure containing such a thermoplastic resin, the above effects can be exhibited more reliably.

The polyolefin-based resin having adhesiveness is not particularly limited, and examples thereof include homopolymers of polypropylene (homopolymers), homopolymers of polyethylene, and propylene-ethylene block copolymers having an EPR phase (rubber phase). , ethylene-vinyl acetate block copolymers, ethylene-ethyl acrylate block copolymers, ethylene-methyl methacrylate block copolymers, etc., and one or more of these may be used in combination, Among them, it is preferably a homopolymer of polyethylene. Polyethylene homopolymers are available at relatively low cost, and those having a melting point of 110° C. or lower are also readily available. Moreover, if it is a homopolymer of polyethylene, transparency can be imparted to the adhesive layer 11 . Therefore, when the substrate layer 15 also has transparency, the protective film 10 has transparency. Therefore, when the protective film 10 is attached to the resin substrate 21 in the step [1] and when the protective film 10 is re-attached to the resin substrate 21 prior to the step [2], dust such as dust is removed. is interposed between the protective film 10 and the resin substrate 21. Therefore, it is possible to reliably prevent the transfer of the laminate 100 in which dust is interposed after the step [2]. As a result, the yield of the obtained sunglasses lens 200 can be improved.

The homopolymer of polyethylene 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). One or more of these can be used in combination.

Further, the elastomer is not particularly limited, but examples thereof include α-polyolefin resin/polyethylene copolymer elastomer, α-polyolefin resin/polypropylene copolymer elastomer, styrene block elastomer, etc. Among them, styrene block elastomer is preferred, and a styrene-olefin-styrene block copolymer elastomer is particularly preferred. In this way, since the elastomer is included in addition to the polyolefin resin, the adhesive layer 11 remains on the resin substrate 21 when the protective film 10 is peeled off from the resin substrate 21 in step [4]. That is, it is possible to accurately suppress or prevent the occurrence of adhesive residue on the resin substrate 21, so that the protective film 10 can be peeled off from the resin substrate 21 more smoothly. By using the elastomer containing styrene as a monomer component, it is possible to more accurately suppress or prevent the occurrence of adhesive deposits on the resin substrate 21 in step [4].

Examples of α-polyolefin resins include 1-hexene, 4-methyl-1-pentene, 1-octene, 1-butene, 1-pentene and 1-heptene.

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, more preferably 10% by weight or more and 18% by weight or less. preferable. As a result, it is possible to accurately suppress or prevent an increase in the hardness of the adhesive layer 11 due to an increase in the styrene content. Therefore, it is possible to reliably maintain the adhesion of the adhesive layer 11 to the resin substrate 21 (coating layer 24 ), and more accurately suppress or prevent the occurrence of adhesive residue on the resin substrate 21 .

Furthermore, examples of styrene-olefin-styrene block copolymers include styrene-isobutylene-styrene block copolymer (SIBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and styrene-butadiene-styrene block copolymer. Copolymers (SBS), styrene-isoprene-styrene copolymers (SIS), and the like can be mentioned, among which styrene-ethylene-butylene-styrene block copolymers (SEBS) are 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 effects described above can be reliably obtained.

In addition, 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 1% by weight or more and 30% by weight or less, more preferably 5% by weight or more and 15% by weight or less. is set to As a result, the effects obtained by including the elastomer in the adhesive layer 11 can be exhibited more remarkably.

Further, as described above, the thermoplastic resin more preferably contains one having a melting point of 110° C. or less. is preferably 110°C or lower, and more preferably, the melting point of the polyolefin resin is 70°C or higher and lower than 110°C. As a result, the effect obtained by setting the surface roughness Ra of the surface of the adhesive layer 11 on the resin substrate 21 side to 0.20 μm or less, that is, the once peeled protective film 10 is superior to the resin substrate 21 In particular, the effect of being able to re-stick with good re-adhering properties can be exhibited remarkably.

In this specification, the melting point of each layer constituting the protective film 10 including the adhesive layer 11 is the melting point of the constituent material having the melting point among the constituent materials contained in each layer (peak temperature by DSC measurement). is multiplied by the ratio of each constituent material contained.

In the adhesive layer 11 having such a configuration, as described above, the surface roughness Ra on the surface of the resin substrate 21 side measured according to JIS B 0601 is set to 0.20 μm or less, but 0.16 μm. It is preferably 0.01 μm or more and 0.12 μm or less. As a result, as shown in FIG. 2(b), the protective film 10 that has been peeled once is re-attached to the resin substrate 21 (see FIG. 3(c)). In addition, excellent re-adherence to the resin substrate 21 can be exhibited.

The average thickness of the adhesive layer 11 is preferably 5 μm or more and 40 μm or less, more preferably 10 μm or more and 20 μm or less. Thereby, the function as the adhesion layer 11 mentioned above can be exhibited reliably.

<<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 when the resin substrate 21 is punched and thermally bent in the steps [2] and [3], the resin substrate As a protective layer (functional layer) for protecting (masking) 21 and peeling (separating) the resin substrate 21 (protective film 10) from the mold used for thermal bending after the thermal bending in the step [3] It works.

Further, in the step [4], when the protective film 10 is peeled off from the thermally bent resin substrate 21, peeling does not occur between the base material layer 15 and the adhesive layer 11, and the adhesive layer 11 is On the other hand, it is for exhibiting excellent adhesiveness.

In order to allow the base layer 15 to exhibit these functions, in the present invention, as shown in FIG. 16 and a second layer 17 positioned on the adhesive layer 11 side, that is, on the resin substrate 21 side.

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 protects (masks) the resin substrate 21 during punching and thermal bending of the resin substrate 21 in the steps [2] and [3]. It functions as the outermost layer for

The first layer 16 should maintain excellent releasability from the mold after thermal bending in step [3], that is, the first layer 16 should not adhere to the mold (mold). For this purpose, the melting point of the first layer 16 is preferably 150° C. or higher, more preferably about 155° C. or higher and 170° C. or lower. Here, as described above, the heating temperature of the coating layer 24 (resin substrate 21) during the thermal bending in the step [3] is preferably set to approximately 110° C. or higher and 160° C. or lower. 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 being melted or softened during the thermal bending in the step [3]. Therefore, after the thermal bending in the step [3], the laminate 100 can be reliably removed from the mold.

The first layer 16 contains, as its main material, a thermoplastic resin whose melting point is preferably 150° C. or higher, more preferably about 155° C. or higher and 170° C. or lower. Thereby, the melting point of the first layer 16 can be relatively easily set to 150° C. or higher. Therefore, after the thermal bending in the above step [3], the laminate 100 can maintain excellent releasability from the mold.

Further, when the second layer 17, which will be described later, also contains a thermoplastic resin of 150° C. or higher, the first layer 16 and the second layer 17 can have better adhesion. Therefore, in step [4], when the protective film 10 is peeled off from the thermally bent resin substrate 21, peeling between the first layer 16 and the second layer 17 is accurately prevented. can be suppressed or prevented.

Furthermore, the first layer 16 preferably has a structure in which the first layer 16 contains only a polyolefin resin of 150° C. or higher as the thermoplastic resin of 150° C. or higher. A polyolefin resin having a temperature of 150° C. or higher can be obtained relatively easily and inexpensively as a thermoplastic resin having a temperature of 150° C. or higher.

Further, the polyolefin resin having a melting point of 150° C. or higher is not particularly limited. Copolymers, ethylene-ethyl acrylate copolymers, ethylene-methyl methacrylate copolymers, etc., which have a melting point of 150° C. or higher, may be used alone or in combination of two or more thereof. , a homopolymer of polypropylene having a melting point of 150° C. or higher. As a result, a polyolefin resin having a melting point of 150° C. or higher can be obtained easily and inexpensively. Moreover, transparency can be imparted to the first layer 16 . Therefore, when the second layer 17 and the adhesive layer 11 also have transparency, the protective film 10 has transparency. Therefore, when the protective film 10 is attached to the resin substrate 21 in the step [1] and when the protective film 10 is re-attached to the resin substrate 21 prior to the step [2], dust such as dust is removed. is interposed between the protective film 10 and the resin substrate 21. Therefore, it is possible to reliably prevent the transfer of the laminate 100 in which dust is interposed after the step [2]. As a result, the yield of the obtained sunglasses lens 200 can be improved.

The copolymer may be either a block copolymer or a random copolymer.

The average thickness of the first layer 16 is preferably 2 μm or more and 40 μm or less, more preferably 5 μm or more and 25 μm or less. Thereby, the function as the first layer 16 described above can be reliably exhibited.

<<second layer 17>>
The second layer 17 is located on the side of the adhesive layer 11, that is, on the side of the resin substrate 21, so that it is located between the adhesive layer 11 and the first layer 16 and functions as an intermediate layer that joins them together. It is something to do.

The second layer 17 contains a thermoplastic resin having adhesiveness (adhesiveness) as a main material in order to exhibit the function described above, thereby separating the adhesive layer 11 and the first layer 16 from each other. , through the second layer 17, can be bonded with excellent adhesion. Therefore, in the step [4], when peeling the protective film 10 from the resin substrate 21, the adhesive layer 11 and the second layer 17 and the first layer 16 and the second layer 17 It is possible to precisely suppress or prevent the separation from occurring between them. Therefore, when the resin substrate 21 is punched out in step [2], even if the adhesive layer 11 has a whisker extending toward the resin substrate 21 on the cut surface of the resin substrate 21 formed by the punching, the whisker is removed. The protective film 10 (adhesive layer 11 ) can be peeled off from the resin substrate 21 while the remaining on the cut surface of the resin substrate 21 is appropriately suppressed or prevented.

The thermoplastic resin having adhesiveness (adhesive resin) is not particularly limited, but includes, for example, polyolefin resins, elastomers, acrylic resins, polyurethane resins, etc. One or more of these may be used. can be used in combination, and among them, polyolefin-based resins and elastomers having adhesive properties are preferred. Moreover, when the adhesive layer 11 contains an elastomer, it is particularly preferable to use a combination of a polyolefin resin and an elastomer. As a result, the adhesion between the adhesive layer 11 and the second layer 17 can be improved, and the separation between the adhesive layer 11 and the second layer 17 can be suppressed or prevented accurately. .

Examples of polyolefin resins include ethylene-vinyl acetate copolymer (EVA), ethylene-maleic anhydride copolymer, ethylene-methyl methacrylate copolymer (EMMA), and ethylene-methyl acrylate copolymer. (EMA), ethylene-methacrylic acid copolymer (EMAA), ethylene-acrylic acid copolymer (EAA), ethylene-ethyl acrylic acid copolymer (EEA), ethylene-methacrylate-glycidyl acrylate terpolymer In addition, grafted products obtained by grafting 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 their anhydrides onto various polyolefin resins, Various polyolefin resins include functional group-introduced products in which functional groups such as carboxylic acid groups, hydroxyl groups, amino groups, acid anhydride groups, oxazoline groups, and epoxy groups are introduced, and one or two of these More than one species can be used in combination. Examples of the graft material include maleic acid-grafted EVA and maleic acid-grafted ethylene-α-polyolefin resin copolymer.

Furthermore, as the elastomer, the same elastomer as described as the elastomer contained in the adhesive layer 11 can be used, and among them, the styrene block elastomer is preferable, and in particular, the styrene-olefin-styrene block copolymer elastomer. is preferably In this way, by including styrene as a monomer component in the elastomer, the adhesiveness of the second layer 17 to the adhesive layer 11 is improved. The occurrence can be more accurately suppressed or prevented.

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

Non-adhesive thermoplastic resins include, for example, polyolefin resins, polyesters, polyurethanes, silicone resins, polyamides, polyimides, polyvinyl chlorides, polycarbonates, and the like. Among them, polyolefin-based resins are preferable, and polyolefin-based resins having a melting point of 150° C. or higher are more preferable. Thereby, the said effect can be exhibited more notably.

The polyolefin-based resin is not particularly limited, and examples thereof include homopolymers of polypropylene (homopolymers), homopolymers of polyethylene, propylene-ethylene copolymers, ethylene-vinyl acetate copolymers, and ethylene-ethyl acrylate. Copolymers, ethylene-methyl methacrylate copolymers, etc., can be used alone or in combination of two or more of these, and among them, homopolymers of polypropylene are preferred. . As a result, the polyolefin resin can be obtained easily and inexpensively. Moreover, transparency can be imparted to the second layer 17 . Therefore, when the first layer 16 and the adhesive layer 11 also have transparency, the protective film 10 has transparency. Therefore, when the protective film 10 is attached to the resin substrate 21 in the step [1] and when the protective film 10 is re-attached to the resin substrate 21 prior to the step [2], dust such as dust is removed. is interposed between the protective film 10 and the resin substrate 21. Therefore, it is possible to reliably prevent the transfer of the laminate 100 in which dust is interposed after the step [2]. As a result, the yield of the obtained sunglasses lens 200 can be improved.

Further, 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.

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 alone as non-adhesive thermoplastic resins because they do not have adhesive properties. : 151° C.) is used as a thermoplastic resin with adhesiveness because it has adhesiveness.

From the above, when the second layer 17 contains a non-adhesive thermoplastic resin, the adhesive thermoplastic resin and the non-adhesive thermoplastic resin are an elastomer and a melting point of 150 ° C. or higher. is a preferred combination. By such a combination, it is possible to accurately suppress or prevent peeling between the adhesive layer 11 and the second layer 17 and between the first layer 16 and the second layer 17. can.

The melting point of the second layer 17 having the above structure is preferably 120° C. or higher. Here, as described above, the heating temperature of the coating layer 24 (resin substrate 21) during the thermal bending in the 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 more and less than 150° C., the second layer 17 can be relatively easily melted or softened during the thermal bending in the step [3]. can do. Therefore, in the step [3], the second layer 17 is made to function as an intermediate layer in a molten or softened state, and the position of the first layer 16 is shifted with respect to the surface direction of the resin substrate 21. As a result, a gripping margin is formed by the first layer 16 at the edge of the laminate 100 . Therefore, since the peeling of the protective film 10 in the step [4] can be performed by gripping the gripping margin, this peeling can be easily performed. In the step [3], the second layer 17 can function as an intermediate layer in a molten or softened state to improve the cushioning property of the second layer 17 during molding with a mold. can. As a result, the unevenness of the mold or the unevenness of contaminants unintentionally mixed between the mold and the protective film 10 can be effectively absorbed. Substrate 21 can be obtained with excellent appearance.

Further, when the melting point of the second layer 17 is set to 150° C. or higher, the second layer 17 is suppressed or prevented from being melted or softened during the thermal bending in the step [3]. be able to. Therefore, it is possible to accurately suppress or prevent a decrease in 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 step [4], peeling between the first layer 16 and the second layer 17 is reliably prevented. prevented.

The average thickness of the second layer 17 is preferably 10 μm or more and 60 μm or less, more preferably 10 μm or more and 40 μm or less. Thereby, the function as the second layer 17 described above can be reliably exhibited.

The protective film 10 comprising the adhesive layer 11 and the base layer 15 having the above structure preferably has an elastic modulus at 25° C. of 300 MPa or more and 600 MPa or less, more preferably 300 MPa or more and 500 MPa or less. , more preferably 300 MPa or more and 450 MPa or less, and particularly preferably 300 MPa or more and 400 MPa or less. As a result, the adhesive layer 11 can be said to have excellent flexibility in a low temperature range such as room temperature. The effect obtained by setting the thickness to 2 μm or less, that is, the effect that the once peeled protective film 10 can be reattached to the resin substrate 21 with excellent re-adhering property can be exhibited more remarkably. can.

Specifically, the re-adherence of the protective film 10 is obtained by attaching the protective film 10 on a polycarbonate substrate with a width of 25 mm and a length of 200 mm, holding one end of the protective film 10 in an environment of 25 ° C. After peeling off to a position with a length of 100 mm in the direction of 90°, the one end of the protective film 10 is separated, and the protective film 10 is re-attached to the polycarbonate substrate. Later, the total area in plan view of the regions where the polycarbonate substrate and the protective film are not bonded is preferably less than 1,250 mm ² , more preferably less than 750 mm ² , and more preferably less than 125 mm ² . It is even more preferable to have By setting the total area to the upper limit value or less, it can be said that the protective film 10 has excellent re-adhesion, and the protective film 10 once peeled can be attached to the resin substrate 21. It can be reliably reapplied against. Therefore, it is possible to appropriately suppress or prevent waste of the protective film 10 and the resin substrate 21 . Therefore, the sunglasses lens 200 can be manufactured with a high yield.

At this time, 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 3 or less. is more preferred. It can be said that this protective film 10 has more excellent re-adhesion properties by setting the number to be equal to or less than the upper limit.

Note that each layer of the adhesive layer 11 and the base material layer 15 (the first layer 16 and the second layer 17) provided in the protective film 10 described above contains, in addition to the constituent materials described above, an antiblocking agent, an oxidation Various additives such as inhibitors, light stabilizers and antistatic agents may be included. The content of the additive may be 10% by weight or less, 8% by weight or less, or 0.001% by weight or more, or 0.1% by weight or more. can also

In particular, the first layer 16 preferably contains an antiblocking agent. As a result, the function of the first layer 16, which is capable of maintaining excellent releasability from the mold, can be exhibited more reliably.

Also, as the antiblocking agent, for example, inorganic particles and organic particles can be used, and one or more of these can be used in combination. The inorganic particles are not particularly limited, but examples thereof include particles of silica, zeolite, smectite, mica, vermiculite and talc. Particles of resin, polyester-based resin, polyurethane-based resin, polystyrene-based resin, silicone-based resin, fluorine-based resin, and the like are included.

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 0.5% by weight or more and 10% by weight or less, more preferably It is set to 1% by weight or more and 9% by weight or less. Thereby, the function of the first layer 16 can be exhibited more remarkably.

Intermediate layers containing the above-mentioned additives and the like may be formed between these layers.
Furthermore, the protective film 10 described above may be manufactured by any method, and can be manufactured by using, for example, a co-extrusion method.

Specifically, three extruders are prepared, and the constituent materials of the adhesive layer 11, the first layer 16, and the second layer 17 are placed in these extruders, respectively, and then melted or softened. By extruding, a molten or softened laminate in which these are laminated in layers from the co-extrusion T die is supplied to a sheet forming unit composed of a plurality of cooling rolls, etc., and then this sheet supply unit The protective film 10 is manufactured by cooling the laminate at .

The surface roughness Ra on the side opposite to the second layer of the adhesive layer is determined, for example, by using a cooling roll having a different surface roughness (for example, a metal mirror surface roll) as the cooling roll provided in the sheet forming unit. The desired size can be adjusted by, for example, providing the molding unit with an air chamber or an air knife to blow air onto the surface of the adhesive layer.

Although the protective film of the present invention has been described above, the present invention is not limited to this, and each layer constituting the protective film can be replaced with an arbitrary structure capable of exhibiting the same function. can.

Further, in the above-described embodiment, in FIG. 2, the case where the protective film is re-attached to the resin substrate after part of the protective film is peeled off from the resin substrate has been described. can also be carried out after the entire protective film has been peeled off from the resin substrate.

Furthermore, in the above-described embodiment, the case where the protective film of the present invention is attached to a resin substrate when thermally bending the resin substrate of a lens for sunglasses has been described, but the protective film of the present invention is In addition to being applicable to thermal bending of resin substrates of such sunglasses lenses, for example, it can also be used to thermally bend resin substrates of lenses of goggles, visors of helmets, and the like.

EXAMPLES The present invention will now be described more specifically based on examples. In addition, the present invention is not limited at all by these examples.

1. Preparation of raw materials First, the raw materials used for producing the protective films of each example and each comparative example are as follows.

<<Thermoplastic resin having non-adhesiveness>>
<Polyolefin-based resin having 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 = 0.4 g/10 min)

<Polyolefin resin having a melting point of 120°C or more and less than 150°C>
Linear low-density polyethylene with a melting point of 121° C. (LLDPE, manufactured by Ube Maruzen Polyethylene Co., Ltd., “Umerit 2525F”, MFR=2.5 g/10 min)

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

<Polyolefin-based resin having a melting point of less than 110°C>
Linear low-density polyethylene with a melting point of 93° C. (LLDPE, manufactured by Tosoh Corporation, “Nibolon-Z HF212R”, MFR=2.0 g/10 min)

<<Thermoplastic resin having adhesiveness>>
<Elastomer>
Styrene-ethylene-butylene-styrene block copolymer (SEBS, manufactured by Asahi Kasei Corporation, "Tuftec H1221")
Styrene-butadiene random copolymer hydrogenated product (HSBR, manufactured by JSR, "Dynaron 1320P")

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

<Polyolefin resin having a melting point of 120°C or more and less 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)

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

2. Production of protective film (Example 1)
[1] First, in forming the adhesive layer (innermost layer), LLDPE having a melting point of 121°C as a polyolefin resin and SEBS as an elastomer are kneaded so that the content of SEBS is 10% by weight. An adhesive layer-forming material (resin composition) was prepared.

[2] Next, in forming the second layer (intermediate layer) included in the base material layer, SEBS as a thermoplastic resin having adhesiveness and h having a melting point of 167 ° C. -PP was kneaded so that the content of SEBS was 20% by weight to prepare a second layer-forming material (resin composition).

[3] Next, as a polyolefin resin having a melting point of 150 ° C. or higher for forming the prepared adhesive layer forming material, the prepared second layer forming material, and the first layer (outermost layer), the melting point is 167° C. h-PP were each loaded into three extruders.

[4] Next, by extruding these in a molten state from the three extruders, a molten laminate in which these are laminated in layers is obtained from the co-extrusion T die. By pressing a metal mirror-finished roll against the surface of the adhesive layer, the surface of the adhesive layer is mirror-finished to form the adhesive layer, and then the laminate is cooled to form the first layer, the second layer, and the adhesive layer. Protective films of Example 1 were obtained with average thicknesses of 10 μm, 30 μm and 10 μm, respectively.

The surface roughness Ra of the adhesive layer on the side opposite to the second layer was measured according to JIS B 0601 using a laser microscope (manufactured by Keyence Corporation, "VK9700") and found to be 0.05 µm. rice field.

Furthermore, according to 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 by Shimadzu Autograph (tensile speed: 500 mm / min). , 475 MPa.

(Example 2 to Example 3)
Example 2 to Example 2 in the same manner as in Example 1 except that the formation of the adhesive layer in the step [4] was performed by blowing air onto the surface of the adhesive layer using an air chamber or an air knife. A protective film of Example 3 was obtained.

(Comparative example 1)
Comparative example in the same manner as in Example 1 except that the formation of the adhesive layer in the step [4] was performed by pressing a metal roll that did not have a mirror surface against the adhesive layer 1 protective film was obtained.

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

(Example 4)
A protective film of Example 4 was prepared in the same manner as in Example 1 except that the type of polyolefin resin and the type of elastomer used in the step [1] were changed as shown in Table 1. Obtained.

(Example 5 to Example 6)
Examples 5 to 5 were carried out in the same manner as in Example 4 except that the formation of the adhesive layer in the step [4] was carried out by blowing air onto the surface of the adhesive layer using an air chamber or an air knife. A protective film of Example 6 was obtained.

(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.

(Examples 8 to 9)
Examples 8 to 8 were carried out in the same manner as in Example 7 except that the formation of the adhesive layer in the step [4] was performed by blowing air onto the surface of the adhesive layer using an air chamber or an air knife. A protective film of Example 9 was obtained.

(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.

(Examples 11 to 12)
Examples 11 to 10 were carried out in the same manner as in Example 10 except that the formation of the adhesive layer in the step [4] was carried out by blowing air onto the surface of the adhesive layer using an air chamber or an air knife. A protective film of Example 12 was obtained.

(Example 13)
[1] First, in forming the adhesive layer (innermost layer), LLDPE having a melting point of 93° C. was prepared as a polyolefin resin as an adhesive layer forming material.

[2] Next, b-PP having a melting point of 158° C. was prepared as an adhesive thermoplastic resin for forming the second layer (intermediate layer) included in the base material layer.

[3] Next, an adhesive layer-forming material, a second layer-forming material, and a polyolefin resin having a melting point of 150°C or higher for forming the first layer (outermost layer), h - PP were each housed in 3 extruders.

[4] Next, by extruding these in a molten state from the three extruders, a molten laminate in which these are laminated in layers is obtained from the co-extrusion T die. By pressing a metal mirror-finished roll against the surface of the adhesive layer, the surface of the adhesive layer is mirror-finished to form the adhesive layer, and then the laminate is cooled to form the first layer, the second layer, and the adhesive layer. Protective films of Example 13 were obtained with average thicknesses of 10 μm, 30 μm and 10 μm, respectively. The surface roughness Ra of the adhesive layer on the side opposite to the second layer was measured and found to be 0.06 μm.

(Example 14)
A protective film of Example 14 was obtained in the same manner as in Example 13 except that the formation of the adhesive layer in the step [4] was performed by blowing air onto the surface of the adhesive layer using an air knife. In addition, when the surface roughness Ra of the adhesive layer on the side opposite to the second layer was measured, it was 0.16 μm.

(Example 15)
Except for preparing an anti-blocking agent (Kinoplus FPP-AB05A) as shown in Table 1 in addition to a polyolefin resin having a melting point of 150° C. or higher as a material for forming the first layer (outermost layer) in the step [3]. obtained a protective film of Example 15 in the same manner as in Example 13.

3. Evaluation The protective films of each example and each comparative example were evaluated by the following methods.
<1> Re-adherence of the protective film to the attached substrate First, the protective film of each example and each comparative example having a width of 25 mm and a length of 200 mm is made of polycarbonate, each of which is 30 cm long and 30 cm wide. × 2.0 mm thick substrates (“ ^ECK100UU ” manufactured by Sumitomo Bakelite Co., Ltd.) were sandwiched between each other with the mirror surface facing the protective film side. A protective film was attached to the polycarbonate substrate located on the adhesive layer side.

The polycarbonate constituting 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 surface is imparted by mold transfer. .

Next, after holding the protective film sandwiched between the polycarbonate substrates under the conditions of 25° C. for 30 minutes, hold one end of the protective film in an environment of 25° C. and elongate it in the direction of 90°. After the protective film was peeled off from the polycarbonate substrate to a position of 100 mm, the one end of the protective film was separated, and the protective film was attached to the polycarbonate substrate again.

Then, 1 minute after this re-attachment, the total area (mm ² ) of the region where the polycarbonate substrate and the protective film are not bonded is measured in plan view, and the polycarbonate substrate and the protective film are not bonded. The number of regions was counted, and the obtained total area and number were evaluated based on the following evaluation criteria.

(Evaluation of total area)
The total area of the region where the polycarbonate substrate and the protective film are not bonded is ◎◎: less than 125 mm ² ◎: 125 mm ² or more and less than 750 mm ² ◯: 750 mm ² or more and less than 1,250 mm ² ×: 1, ^250mm2 or more

(Evaluation of number)
The number of regions where the polycarbonate substrate and the protective film are not bonded is ◎◎: 3 or less ◎: More than 3 and less than or equal to 10 ○: More than 10 and less than or equal to 20 ×: More than 20

<2> Evaluation of whether or not whiskers adhere to resin substrates (manufactured by Bakelite Co., Ltd.) by pressing with a roll under the condition of a load of 0.5 kg/cm ² to affix a protective film to obtain a laminate.

Next, after being stored under conditions of a temperature of 23° C. and a time of 12 hours, this laminate, that is, the resin substrate having protective films attached on both sides thereof, is punched out in the thickness direction to form a circular laminate in plan view. It was assumed that

Next, after peeling off the two protective films from the laminate, the presence or absence of residual whiskers (adhesive layer) on the punched surface (cut surface) of the resin substrate 21 was visually observed, and residual whiskers were observed. A case where the beard was not observed was evaluated as ⊚;

<3> Evaluation of the presence or absence of formation of orange peel on the surface of the resin substrate First, each protective film of each example and each comparative example has a structure in which a polarizer is sandwiched between two polycarbonate substrates (polycarbonate layers). A laminated body was obtained by attaching protective films to both surfaces of a resin substrate (manufactured by Sumitomo Bakelite Co., Ltd.) by pressure bonding using rolls under a condition of a load of 0.5 kg/cm ² .

Next, after being stored under conditions of a temperature of 23° C. and a time of 12 hours, this laminate, that is, the resin substrate having protective films attached on both sides thereof, is punched out in the thickness direction to form a circular laminate in plan view. It was assumed that

Next, the circular laminate was subjected to thermal bending under heating using a REMA molding machine ("CR-32 type" manufactured by REMA Co., Ltd.) equipped with a mold.

Next, after peeling off the two protective films from the laminate, the presence or absence of formation of orange peel (unevenness) on the adhered surface (release surface) of the resin substrate 21 was visually observed to determine whether orange peel was formed. The case where no formation of orange peel was observed was evaluated as ◯, and the case where formation of orange peel was observed was evaluated as x.

Table 1 below shows the evaluation results of the protective films of Examples and Comparative Examples obtained as described above.

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

On the other hand, in the protective film of each comparative example, the surface roughness Ra on the surface of the adhesive layer was not set to 0.20 μm or less, and due to this, the polycarbonate substrate and the protective film were not bonded. It was not possible to satisfy the conditions that the total area of the non-bonded regions in plan view is less than 1250 mm ² and that the number of regions where the polycarbonate substrate and the protective film are not bonded is 20 or less. In other words, the protective film could not exhibit re-adherence to the resin substrate.

REFERENCE SIGNS LIST 10 protective film 11 adhesive layer 15 base layer 16 first layer 17 second layer 21 resin substrate 23 polarizer 24 coating layer 30 polycarbonate layer 100 laminate 200 lens for sunglasses

Claims (9)

A protective film that is used by being attached to a resin substrate when the resin substrate is subjected to thermal bending under heating,
a base layer;
an adhesive layer positioned between the base material 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 protective film, wherein the adhesive layer has a surface roughness Ra of 0.20 μm or less on the surface on the resin substrate side, measured according to JIS B 0601. The protective film according to claim 1, wherein the protective film has an elastic modulus of 300 MPa or less and 600 MPa or less at 25°C. The first layer contains a thermoplastic resin as a main material and has a melting point of 150° C. or higher, and the second layer contains a thermoplastic resin as a main material and has a melting point of 120° C. or higher. The protective film according to claim 1 or 2, wherein the adhesive layer contains a thermoplastic resin as a main material and has a melting point of 110°C or less. The protective film according to claim 3, wherein both the thermoplastic resin contained in the first layer and the thermoplastic resin contained in the second layer contain a polyolefin resin. 5. The protective film according to any one of claims 1 to 4, wherein the adhesive layer contains an adhesive polyolefin resin as a main material. The protective film with 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 the direction of 90° to the position of length 100. Later, when the protective film is attached again to the polycarbonate substrate by separating the one end of the protective film, the polycarbonate substrate and the protective film are not bonded 1 minute after the re-attachment. The protective film according to any one of claims 1 to 5, wherein the total area of the regions in plan view is less than 1250 ^mm2 . The protective film according to any one of claims 1 to 6, which is attached to both sides of the resin substrate. The resin substrate is provided with a coating layer composed of a single layer or laminate having at least one of a polycarbonate resin layer, a polyamide resin layer and a cellulose resin layer on both sides, one side or the other side. Item 8. The protective film according to any one of Items 1 to 7. The protective film according to any one of claims 1 to 8, wherein the resin substrate is subjected to the thermal bending process by press molding or vacuum molding.

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