JPWO2018199172A1 - Protective film - Google Patents

Abstract

The protective film 10 of the present invention is used by being adhered to the resin substrate 21 when the resin substrate 21 is subjected to hot bending under heating. The protective film 10 has a base layer and an adhesive layer that is located between the base layer and the resin substrate 21 and adheres to the resin substrate 21. The pressure-sensitive adhesive layer contains a polyolefin and a styrene block elastomer having a styrene content of 25% by weight or less.

Description

  The present invention relates to a protective film that is used by being adhered to a resin substrate when the resin substrate is subjected to heat bending under heating.

  There is a sunglass lens provided with a resin substrate having a configuration in which both surfaces of a polarizer are coated with a coating layer made of a polycarbonate resin, a polyamide resin, or a cellulose resin. Such a sunglass lens is manufactured, for example, as follows. First, protective films are attached to both surfaces of the resin substrate having a plate shape in plan view. In this state, the resin substrate is punched into a predetermined shape such as a circular shape in plan view. Thereafter, the resin substrate is subjected to heat bending under heating. Then, the protective film is peeled off from the thermally bent resin substrate. Thereafter, a polycarbonate layer is injection-molded on the concave surface of the resin substrate. Thereby, a lens for sunglasses is manufactured.

  This protective film includes, for example, a base material and an adhesive layer. Specifically, a protective film having a configuration in which a base material mainly composed of a polyolefin-based resin is adhered to the resin substrate via an adhesive layer mainly composed of polyethylene, ethylene-propylene copolymer, or the like. It has been proposed (for example, see Patent Document 1).

  However, in the protective film having such a configuration, the protective film can be attached to the resin substrate without being peeled at the time of punching the resin substrate and at the time of hot bending (particularly, at the time of hot bending). However, the following problem occurs. there were. That is, the protective film having the above-described configuration tends to have a higher adhesion strength to the resin substrate after the hot bending process. As a result, when the protective film is peeled off from the resin substrate, glue residue originating from the adhesive layer is formed on the resin substrate, which causes a problem of lowering the yield of manufactured sunglass lenses.

  Note that such a problem occurs not only with the above-described sunglass lens but also with a resin substrate such as a lens included in goggles and a visor included in a helmet.

JP 2003-145616 A

  An object of the present invention is to allow the resin substrate to be adhered to the resin substrate without being peeled off at the time of hot bending, and to peel off the protective film from the adhesive layer when peeling the protective film from the resin substrate after the hot bending. It is an object of the present invention to provide a protective film capable of accurately suppressing or preventing the occurrence of odor on a resin substrate.

Such an object is achieved by the present invention described in the following (1) to (8).
(1) A protective film to be attached to a resin substrate when the resin substrate is subjected to hot bending under heating,
A base layer, and an adhesive layer that is located between the base layer and the resin substrate and adheres to the resin substrate,
A protective film, wherein the adhesive layer contains a polyolefin and a styrene block elastomer having a styrene content of 25% by weight or less.

  (2) The protective film according to (1), wherein the styrene block elastomer includes a styrene-olefin-styrene block copolymer.

  (3) The protective film according to (1) or (2), wherein the polyolefin has a melting point of 150 ° C. or more.

  (4) The polyolefin has a melt flow rate measured at a heating temperature of 230 ° C. and a load of 2.16 kgf in accordance with JIS K7210 of not less than 0.5 g / 10 min and not more than 10.0 g / 10 min. The protective film according to any one of 1) to (3).

  (5) The protective film according to any one of (1) to (4), wherein the polyolefin includes a homopolymer of polypropylene.

  (6) The protective film according to any one of (1) to (5), which is attached to both surfaces of the resin substrate.

  (7) On both surfaces, one surface or the other surface of the resin substrate, a coating layer composed of a single layer or a laminate having at least one of a polycarbonate resin layer, a polyamide resin layer and a cellulose resin layer is provided. The protective film according to any one of the above (1) to (6).

  (8) The protective film according to any one of (1) to (7), wherein the resin substrate is subjected to the hot bending by press molding or vacuum molding.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to stick to a resin substrate without peeling at the time of the heat bending of a resin substrate, when peeling a protective film from a resin substrate after a heat bending, the adhesive residue derived from an adhesive layer Can be accurately suppressed or prevented from occurring on the resin substrate. Therefore, when the resin substrate is applied to, for example, a resin substrate included in a sunglass lens, the sunglass lens can be manufactured with high yield.

FIG. 1 is a schematic diagram for explaining a method for manufacturing a sunglass lens using a protective film. FIG. 2 is a longitudinal sectional view showing a preferred embodiment of the protective film of the present invention.

  Hereinafter, the protective film of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

  The protective film of the present invention is a protective film that is used by being attached to a resin substrate when the resin substrate is subjected to hot bending under heating. Such a protective film 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, wherein the adhesive layer has a polyolefin content of styrene. Contains 25% by weight or less of a styrene block elastomer.

  By adopting such a configuration of the adhesive layer included in the protective film, the protective film can be attached to the resin substrate without being peeled off during the hot bending of the resin substrate, and the protective film is peeled off from the resin substrate after the hot bending. In this case, it is possible to accurately suppress or prevent the generation of adhesive residue derived from the adhesive layer on the resin substrate. Therefore, when the resin substrate is applied to, for example, a resin substrate included in a sunglass lens, the sunglass lens can be manufactured with high yield.

  Hereinafter, prior to describing the protective film of the present invention, a method of manufacturing a sunglass lens manufactured using the protective film of the present invention will be described.

<Production method for sunglass lens>
FIG. 1 is a schematic diagram for explaining a method for manufacturing a sunglass lens using a protective film. In the following, for convenience of explanation, the upper side of FIG. 1 is referred to as “upper”, and the lower side is referred to as “lower”.

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

  In this embodiment, a resin substrate 21 including a polarizer 23 and a coating layer 24 is prepared. The polarizer 23 functions as an optical element that extracts linearly polarized light having a polarization plane in one predetermined direction from unpolarized natural light. The coating layer 24 covers both surfaces of the polarizer 23. In this resin substrate 21, the coating layer 24 is formed of a single layer or a laminate having at least one of a polycarbonate resin layer, a polyamide resin layer, and a cellulose resin layer such as triacetyl cellulose. . Further, as shown in FIG. 1A, the coating layer 24 is formed on both surfaces (both surfaces) of the polarizer 23, and also on the upper surface (one surface) and the lower surface (the other surface). It may be formed on any of them.

  [2] Next, as shown in FIG. 1B, the prepared laminate 100, that is, the resin substrate 21 in a state where the protective films 10 are adhered to both surfaces of the resin substrate 21, is punched in the thickness direction. . Thereby, the laminated body 100 is formed in a circular shape in plan view.

[3] Next, as shown in FIG. 1C, the laminate 100 having a circular shape is subjected to heat bending under heating.
This hot bending is usually performed by press forming or vacuum forming.

  As described above, in the present embodiment, the resin substrate 21 includes the covering layer 24, and the covering layer 24 has a single-layer structure or a laminate including at least one of a polycarbonate resin layer, a polyamide resin layer, and a cellulose resin layer. It consists of a body. For this reason, the heating temperature (forming temperature) of the laminate 100 (resin substrate 21) at the time of hot bending is preferably about 110 ° C. or more and 150 ° C. or less in consideration of the melting or softening temperature of the coating layer 24. Preferably, it is set at about 140 ° C. or more and about 150 ° C. or less. By setting the heating temperature within such a range, the resin substrate 21 can be reliably bent while the resin substrate 21 is in a softened or molten state while preventing deterioration and deterioration of the resin substrate 21.

  [4] Next, as shown in FIG. 1 (d), after the protective film 10 is peeled from the thermally bent resin substrate 21, that is, the laminate 100, the concave surface of the resin substrate 21 is made of polycarbonate resin. The polycarbonate layer 30 to be formed is injection molded. Note that a polyamide layer made of, for example, a polyamide resin may be formed on the concave surface of the resin substrate 21 instead of the polycarbonate layer 30.

  Thus, the sunglass lens 200 including the thermally bent resin substrate 21 is manufactured.

  By applying the protective film of the present invention to the above-described method for manufacturing a sunglass lens, the resin substrate 21 in the step [2] and the step [3] can be used without peeling the protective film 10 from the resin substrate 21. Of the protective film 10 from the resin substrate 21 in the step [4], and the occurrence of adhesive residue derived from the adhesive layer 11 on the resin substrate 21 is accurately suppressed or It can be implemented with prevention. Hereinafter, the protective film of the present invention will be described in detail.

  In the protective film 10 of the present invention, the pressure-sensitive adhesive layer 11 only needs to contain a polyolefin and a styrene block elastomer having a styrene content of 25 wt% or less, and the configuration of the base layer 15 is not particularly limited. Hereinafter, a case where the base material layer 15 is configured by a laminate of the first layer 16 and the second layer 17 will be described as an example.

<Protective film 10>
FIG. 2 is a longitudinal sectional view showing a preferred embodiment of the protective film of the present invention. In the following, for convenience of description, the upper side of FIG. 2 is referred to as “upper”, and the lower side is referred to as “lower”.

  The protective film 10 includes a base layer 15 and an adhesive layer 11 that is located between the base layer 15 and the resin substrate 21 and that adheres (joins) to the resin substrate 21. As shown in FIG. 2, in the present embodiment, the base layer 15 includes the first layer 16 located on the opposite side of the adhesive layer 11, that is, the first layer 16 located on the mold side, and the adhesive layer 11 side, that is, the resin substrate 21. And a second layer 17 located on the side.

Hereinafter, each of these layers will be described in detail.
<< 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. Thus, the adhesive layer 11 has a function of joining the base material layer 15 to the resin substrate 21.

  In the present invention, as described above, the adhesive layer 11 contains a polyolefin and a styrene block elastomer having a styrene content of 25% by weight or less.

  As described above, since the adhesive layer 11 contains the styrene block elastomer having a styrene content of 25 wt% or less, when the protective film 10 is peeled off from the resin substrate 21 in the step [4], The adhesive layer 11 can be accurately suppressed or prevented from remaining. That is, it is possible to accurately suppress or prevent the generation of adhesive residue derived from the adhesive layer 11 on the resin substrate 21.

  The styrene block elastomer (styrene-based elastomer having a styrene block) is not particularly limited, but is preferably a styrene-olefin-styrene block copolymer elastomer. As described above, when the styrene content is 25 wt% or less by using the styrene-olefin-styrene block copolymer as the styrene block elastomer containing styrene as a monomer component, in the step [4], the resin The generation of adhesive residue on the substrate 21 can be more accurately suppressed or prevented.

  Examples of the styrene-olefin-styrene block copolymer include styrene-isobutylene-styrene block copolymer (SIBS), styrene-ethylene-butylene-styrene block copolymer (SEBS), and styrene-butadiene-styrene block. Copolymer (SBS), styrene-isoprene-styrene copolymer (SIS) and the like. Among them, styrene-ethylene-butylene-styrene block copolymer (SEBS) is preferable. By selecting SEBS as the styrene-olefin-styrene block copolymer, the styrene content in the elastomer can be relatively easily set at 25 wt% or less, and the above-described effects can be more reliably obtained. it can.

  Furthermore, the content of styrene in the elastomer may be 25 wt% or less, but is preferably 10 wt% or more and 18 wt% or less. Thereby, it is possible to accurately suppress or prevent the increase in the hardness of the adhesive layer 11 due to the increase in the styrene content. Therefore, it is possible to more accurately suppress or prevent the occurrence of adhesive residue on the resin substrate 21 while reliably maintaining the adhesion of the adhesive layer 11 to the resin substrate 21 (the covering layer 24).

  The content of the elastomer in the adhesive layer 11 is not particularly limited, but is preferably set to 20 wt% or more and 80 wt% or less, more preferably 30 wt% or more and 60 wt% or less. Thereby, the effect obtained by allowing the adhesive layer 11 to contain a styrene block elastomer having a styrene content of 25 wt% or less can be more remarkably exhibited.

  Further, in the present invention, as described above, the adhesive layer 11 contains a polyolefin in addition to the styrene block elastomer having a styrene content of 25 wt% or less.

  As described above, since the pressure-sensitive adhesive layer 11 contains polyolefin, the resin substrate 21 can be punched and thermally bent in the step [2] and the step [3] without peeling the protective film 10 from the resin substrate 21. The peeling of the protective film 10 from the resin substrate 21 in the step [4] can be performed relatively easily.

  Further, the melting point of the polyolefin is preferably 150 ° C. or higher, more preferably 155 ° C. or higher and 160 ° C. or lower. By setting the melting point of the polyolefin in such a temperature range, the effect obtained by including the polyolefin in the adhesive layer 11 can be more remarkably exhibited.

Here, the easy peelability of the protective film 10 from the resin substrate 21 can be expressed by using the peel strength. Specifically, the protective film 10 is attached to the coating layer 24 to obtain a laminate. Thereafter, the peel strength T ₁ between the coating layer 24 and the protective film 10 measured according to JIS C-6481: 1996 after storing the laminate under the conditions of a temperature of 50 ° C. and a time of 12 hours, and temperature 150 ℃, JIS C-6481 after storage of the laminate under conditions of time 5min: is measured according to 1996, the peel strength _{T 2} of the between the covering layer 24 and the protective film 10, respectively, 0 It is preferably from 0.05 N / 25 mm to 3.0 N / 25 mm, more preferably from 0.10 N / 25 mm to 1.5 N / 25 mm, and more preferably from 0.15 N / 25 mm to 0.5 N / 25 mm. Is more preferable. Temperature 50 ° C., the time 12hr conditions and temperatures 0.99 ° C. for a time under conditions of 5min, respectively, the peel strength _{T 1} and peel strength _{T 2} of the after storage a laminate by the above range, the step [2 ] And the bending of the resin substrate 21 in the step [3] and the thermal bending can be performed without peeling the protective film 10 from the resin substrate 21. Even if the protective film 10 has passed, the peeling of the protective film 10 from the resin substrate 21 in the step [4] can be reliably performed.

  The polyolefin is not particularly limited, and may be, for example, a homopolymer of polypropylene (homopolymer), a homopolymer of polyethylene, a propylene-ethylene block copolymer having an EPR phase (rubber phase), or an ethylene-vinyl acetate block. Copolymers, ethylene-ethyl acrylate block copolymers, ethylene-methyl methacrylate block copolymers and the like can be mentioned, and one or more of these can be used in combination. Among these, a homopolymer of polypropylene (homopolymer) is preferable. A polypropylene homopolymer can be obtained relatively inexpensively, and a polypropylene homopolymer having a melting point of 150 ° C. or more can be easily obtained. In addition, if it is a homopolymer of polypropylene, transparency can be imparted to the adhesive layer 11. Therefore, when the base material layer 15 also has transparency, the protective film 10 can have transparency. Therefore, at the time of attaching the protective film 10 to the resin substrate 21 in the step [1], it is possible to visually check whether dust such as dust is interposed between the protective film 10 and the resin substrate 21. Therefore, it is possible to reliably prevent the stack 100 in which dust is present from being transferred after the step [2]. As a result, the yield of the obtained sunglass lens 200 is improved.

  Further, the polyolefin has a melt flow rate (MFR) of 0.5 g / 10 min or more and 10.0 g / 10 min or less measured under the conditions of a heating temperature of 230 ° C. and a load of 2.16 kgf in accordance with JIS K7210. It is preferably 1.0 g / 10 min or more and 5.0 g / 10 min or less, more preferably 2.0 g / 10 min or more and 3.5 g / 10 min or less. As a result, the adhesive layer 11 having excellent initial conformability to the coating layer 24 is obtained, so that the protective film 10 can be attached to the resin substrate 21 in the step [1] with excellent adhesion.

  In the present specification, the melting point of each layer constituting the protective film 10 including the adhesive layer 11 refers to the melting point (peak temperature by DSC measurement) of each constituent material contained in each layer, respectively. The value determined by the sum of the products multiplied by the included ratio is defined as the melting point.

  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 above-mentioned adhesive layer 11 can be reliably exhibited.

<<< base material layer 15 >>>
The base material layer 15 is joined to the resin substrate 21 (the covering layer 24) via the adhesive layer 11. The base material layer 15 functions as a functional layer (protective layer) for protecting (masking) the resin substrate 21 at the time of punching and thermal bending of the resin substrate 21 in the steps [2] and [3]. is there.

  The base material layer 15 may have any configuration as long as it exhibits such a function, and may be a single-layer body or a laminate. In the present embodiment, as shown in FIG. 2, the base layer 15 includes the first layer 16 located on the opposite side of the adhesive layer 11, that is, the first layer 16 located on the mold side, and the adhesive layer 11 side, that is, the resin substrate 21. A case is described in which it is constituted by a laminate having the second layer 17 located on the side.

<<< first layer 16 >>>
The first layer 16 is located on the opposite side of the adhesive layer 11, that is, on the mold side during the thermal bending in the step [3], and functions as an outermost layer for protecting the resin substrate 21.

  This first layer 16 is to maintain excellent releasability from the mold after the thermal bending in the step [3], that is, to prevent the first layer 16 from being in close contact with the mold (die). For the purpose, the melting point of the first layer 16 is preferably 150 ° C. or higher, more preferably about 155 ° C. or higher and 165 ° C. or lower. Here, as described above, the heating temperature of the coating layer 24 (the resin substrate 21) at the time of the thermal bending in the step [3] is preferably set to about 110 ° C. or more and about 150 ° C. or less. 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 in a molten or softened state during the thermal bending in the step [3]. Therefore, after the thermal bending in the step [3], the laminate 100 can be reliably separated from the mold.

  As a constituent material of such a first layer 16, a thermoplastic resin having a melting point of preferably 150 ° C. or more is preferably used, and more preferably, a polyolefin having a melting point of 150 ° C. or more is selected. This makes it possible to easily set the melting point of the first layer 16 to 150 ° C. or higher. When the second layer 17 described later also includes a polyolefin, the adhesion between the base layer 15 (the first layer 16 and the second layer 17) and the adhesive layer 11 can be improved. Therefore, it is possible to accurately suppress or prevent the occurrence of peeling in each layer of the protective film 10.

  The polyolefin having a melting point of 150 ° C. or higher includes, for example, a polyolefin having a melting point of 150 ° C. or higher among the polyolefins contained in the adhesive layer 11 described above.

  The average thickness of the first layer 16 is preferably 10 μm or more and 50 μm or less, and more preferably 15 μm or more and 35 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 adhesive layer 11 side, that is, on the resin substrate 21 side, and functions as an intermediate layer located between the adhesive layer 11 and the first layer 16.

  The second layer 17 is in a molten and softened state during the thermal bending in the step [3], and the first layer 16 protrudes at the edge of the curved surface of the multilayer body 100 due to the thermal bending of the multilayer body 100. It is provided on the base material layer 15 for the purpose of functioning as an intermediate layer for forming a gripping sill. For this reason, the melting point of the second layer 17 is preferably less than 120 ° C., and more preferably about 90 ° C. or more and 119 ° C. or less. 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 about 110 ° C. or more and 150 ° C. or less. Therefore, by setting the melting point of the second layer 17 as described above, the second layer 17 can be reliably melted or softened during the thermal bending in the step [3]. Therefore, in the step [3], the second layer 17 functions as an intermediate layer in a molten or softened state, and displaces the first layer 16 with respect to the surface direction of the resin substrate 21. I can make it. As a result, a gripping white by the first layer 16 is formed at the edge of the stacked body 100. For this reason, the peeling of the protective film 10 in the step [4] can be performed by grasping a grasping sill, so that the peeling can be easily performed.

Further, the length of the gripping white and L _1, a diameter in plan view after it has been bent heat and L ₂ laminate 100 forms a circular shape in plan view by the step [3], the step [3] (L ₁ / L ₂ ) × 100 is preferably 0.1% or more and 1% or less, and more preferably 0.2% or more when the radius of curvature R of the laminate 100 that is thermally bent by the above is 8.5 cm. More preferably, it is 0.5% or less. By satisfying such a relationship, the protective film 10 can be reliably peeled off in the step [4] using the gripping sill formed in the step [3].

  As a constituent material of such a second layer 17, a thermoplastic resin having a melting point of preferably less than 120 ° C. is preferably used, and a polyolefin having a melting point of less than 120 ° C. is more preferably selected. This makes it possible to easily set the melting point of the second layer 17 to less than 120 ° C. When the first layer 16 also includes a polyolefin, the adhesion between the base layer 15 (the first layer 16 and the second layer 17) and the adhesive layer 11 can be improved. Therefore, it is possible to accurately suppress or prevent the occurrence of peeling in each layer of the protective film 10.

  In addition, as a polyolefin having a melting point of less than 120 ° C., a polyolefin having a melting point of less than 120 ° C. among the polyolefins contained in the adhesive layer 11 described above is exemplified. Examples thereof include a homopolymer of polyethylene having a melting point of less than 120 ° C., an α-olefin / polyethylene copolymer, and an α-olefin / polypropylene copolymer.

  The second layer 17 preferably has an average thickness of 10 μm or more and 60 μm or less, and more preferably 15 μm or more and 30 μm or less. Thereby, the function as the second layer 17 described above can be reliably exhibited.

The adhesive layer 11 and the base layer 15 (the first layer 16 and the second layer 17) included in the above-described protective film 10 have an antioxidant and a light, respectively, in addition to the constituent materials described above. Various additives such as a stabilizer and an antistatic agent may be contained.
Further, an intermediate layer containing the above-mentioned additives and the like may be formed between these layers.

  Further, the above-described protective film 10 may be manufactured by any method, and for example, may be manufactured by using 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 stored in these extruders, respectively. Thereafter, these constituent materials are extruded in a molten or softened state. Thereby, a laminated body in a molten or softened state, in which these constituent materials are laminated in a layer, is obtained from the co-extruded T-die. The obtained laminate is supplied to a sheet forming section composed of a plurality of cooling rolls and the like, and then the laminate is cooled in the sheet forming section, whereby the protective film 10 is manufactured.

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

  Furthermore, in the said embodiment, the case where the protective film of this invention was affixed to the resin substrate at the time of performing a heat bending process with respect to the resin substrate which a lens for sunglasses uses was used. However, the protective film of the present invention is applicable not only to the thermal bending of the resin substrate of such a sunglass lens, but also to the use of, for example, a lens provided in goggles and a visor provided in a helmet. be able to.

  Hereinafter, the present invention will be described more specifically based on examples. Note that the present invention is not limited at all by these examples.

1. Examination of types of elastomer contained in adhesive layer 1-1. Preparation of Raw Materials First, the raw materials used for producing the protective films of the respective examples and comparative examples are as follows.

<Polyolefin>
A random polypropylene having a melting point of 145 ° C. (“Novatech EG8B”, manufactured by Nippon Polypropylene Co., Ltd., MFR = 0.8 g / 10 min)
Homopolypropylene having a melting point of 158 ° C. (manufactured by Nippon Polypropylene, “Novatec EA9”, MFR = 0.5 g / 10 min)
Linear low density polyethylene having a melting point of 119 ° C. (Ube Maruzen Polyethylene Co., Ltd., “Ulimet 1540F”, MFR = 4.0 g / 10 min)

<Elastomer>
Styrene-ethylene-butylene-styrene block copolymer (SEBS) having a styrene content of 12% by weight ("TUFTEC H1221" manufactured by Asahi Kasei Corporation)
Styrene-ethylene-butylene-styrene block copolymer (SEBS) having a styrene content of 20% by weight ("TUFTEC H1052" manufactured by Asahi Kasei Corporation)
Styrene-isobutylene-styrene block copolymer (SIBS) having a styrene content of 20% by weight (“Sivstar 062H” manufactured by Kaneka Corporation)
α-olefin / polypropylene copolymer elastomer (“Tuffmer PN2060” manufactured by Mitsui Chemicals, Inc.)
α-Olefin / polyethylene copolymer elastomer (“Kernel KF350”, manufactured by Japan Polyethylene Corporation)
Styrene-ethylene-butylene-styrene block copolymer (SEBS) having a styrene content of 30% by weight (manufactured by Asahi Kasei Corporation, “product number Tuftec H1041”)

1-2. Production of protective film (Example 1A)
[1A] First, in forming an adhesive layer, an adhesive layer forming material is kneaded with SEBS having a styrene content of 12 wt% and random polypropylene having a melting point of 145 ° C. so that the SEBS content becomes 50 wt%. (Resin composition) was prepared.

  [2A] Next, the prepared adhesive layer forming material, low density polyethylene having a melting point of 119 ° C. as a second layer (intermediate layer) forming material, and a melting point of 158 ° C. as a first layer (outermost layer) forming material And homopolypropylene were stored in three extruders, respectively.

  [3A] Next, these extruders were extruded in a molten state from three extruders. As a result, a laminated body in a molten state in which these forming materials were laminated in layers was obtained from the co-extruded T-die. Thereafter, the laminate was cooled to obtain a protective film of Example 1A.

(Examples 2A to 7A, Comparative Examples 1A to 3A)
The type of elastomer used in place of SEBS having a styrene content of 12 wt% in the step [1A], the content of the elastomer contained in the adhesive layer forming material prepared in the step [1A], and the formation in the step [3A] Examples 2A to 7A and Comparative Examples 1A to 3A in the same manner as in Example 1A, except that the average thickness of the pressure-sensitive adhesive layer in the laminated body was changed as shown in Table 1. Was obtained.

1-3. Evaluation The protective film of each example was evaluated by the following method.

<1> Evaluation of Adhesion Before Thermal Bending First, with respect to the protective films of Examples and Comparative Examples, a resin substrate having a configuration in which a polarizer was sandwiched (covered) by two polycarbonate substrates (polycarbonate layers) was used. "P1352" manufactured by Sumitomo Bakelite Co., Ltd.) was prepared. Each protective film was pressure-bonded to both surfaces of each resin substrate using a roll under a load of 0.5 kg / cm ² , and the protective film was attached to obtain a laminate.

  Next, the peel strength between the polycarbonate substrate and the protective film was measured according to JIS C-6481: 1996. Then, the obtained peel strength was evaluated based on the following evaluation criteria.

A: The peel strength is 0.10 N / 25 mm or more and 1.5 N / 25 mm or less.
B: The peel strength is 0.05 N / 25 mm or more and less than 0.10 N / mm, or 1.5 N / 25 mm or more and 3.0 N / 25 mm or less.
C: The peel strength is less than 0.05 N / 25 mm or more than 3.0 N / 25 mm.

<2> Evaluation of adhesive residue after thermal bending First, a resin substrate (Sumitomo Bakelite Co., Ltd.) having a configuration in which a polarizer was sandwiched between two polycarbonate substrates (polycarbonate layers) was used for each of the protective films of Examples and Comparative Examples. , “P1352”). Each protective film was pressure-bonded to both surfaces of each resin substrate using a roll under a load of 0.5 kg / cm ² , and the protective film was attached to obtain a laminate.

  Next, while heating the obtained laminate at a heating temperature of 150 ° C., the laminate was thermally bent by vacuum forming. About the laminated | stacked body which carried out the heat bending, the protective film was peeled from the polycarbonate substrate, and after that, the presence or absence of the adhesive residue in the polycarbonate substrate was observed. Then, the observation result of the presence or absence of the adhesive residue was evaluated based on the following evaluation criteria.

A: No adhesive residue is observed.
B: Some adhesive residue is observed.
C: Clear adhesive residue is observed.

  The evaluation results of the protective films of the respective examples and comparative examples obtained as described above are shown in Table 1 below.

  As shown in Table 1, in each example, a styrene-olefin-styrene block copolymer having a styrene content of 25% by weight or less was used as an elastomer in the adhesive layer of the protective film. For this reason, in the protective film in each example, in the laminate of the polycarbonate substrate and the protective film after the heat bending, the protective film can be easily peeled from the polycarbonate substrate without any adhesive residue on the polycarbonate substrate. Became clear.

  On the other hand, in the protective film in each comparative example, an elastomer containing no styrene or a styrene-olefin-styrene block copolymer having a styrene content of more than 25 wt% was used as the elastomer contained in the adhesive layer. For this reason, in the protective film in each comparative example, when the protective film was peeled off from the polycarbonate substrate, a result was observed in which a clear adhesive residue was recognized on the polycarbonate substrate.

2. Examination of melting point of polyolefin contained in adhesive layer 2-1. Preparation of Raw Materials First, the raw materials used for producing the protective film of each example are as follows.

<Polyolefin>
Homopolypropylene having a melting point of 158 ° C. (manufactured by Sumitomo Chemical Co., Ltd., “Nobrene FS2011DG2”, MFR = 2.5 g / 10 min)
Homopolypropylene having a melting point of 158 ° C. (manufactured by Nippon Polypropylene, “Novatec EA9”, MFR = 0.5 g / 10 min)
Homopolypropylene having a melting point of 158 ° C. (manufactured by Sumitomo Chemical Co., Ltd., “Nobrene WF836DG3”, MFR = 7.0 g / 10 min)
Block polypropylene having a melting point of 155 ° C. (a propylene-ethylene block copolymer having an EPR phase (rubber phase)) (manufactured by Nippon Polypropylene, “Novatec EC9GD”, MFR = 0.5 g / 10 min)
A random polypropylene having a melting point of 145 ° C. (“Novatech EG8B”, manufactured by Nippon Polypropylene Co., Ltd., MFR = 0.8 g / 10 min)
Linear low density polyethylene having a melting point of 119 ° C. (Ube Maruzen Polyethylene Co., Ltd., “Ulimet 1540F”, MFR = 4.0 g / 10 min)
Random polypropylene having a melting point of 132 ° C. (manufactured by Sumitomo Chemical Co., Ltd., “Nobrene S131”, MFR = 1.5 g / 10 min)
Linear low density polyethylene having a melting point of 121 ° C. (Ube Maruzen Polyethylene Co., Ltd., “Ulimet 2525F”, MFR = 2.5 g / 10 min)
Linear low-density polyethylene having a melting point of 98 ° C. (manufactured by Prime Polymer Co., Ltd., “Evolu SP0540”, MFR = 3.8 g / 10 min)

<Elastomer>
Styrene-ethylene-butylene-styrene block copolymer (SEBS) having a styrene content of 20% by weight ("TUFTEC H1052" manufactured by Asahi Kasei Corporation)

2-2. Production of protective film (Example 1B)
[1B] First, in forming the adhesive layer, SEBS having a styrene content of 20 wt% and homopolypropylene (Nobrene FS2011DG2) having a melting point of 158 ° C. are kneaded so that the SEBS content becomes 50 wt%. An adhesive layer forming material (resin composition) was prepared.

  [2B] Next, the prepared adhesive layer forming material, a linear low density polyethylene having a melting point of 119 ° C. as a second layer (intermediate layer) forming material, and a melting point as a first layer (outermost layer) forming material And 158 ° C. homopolypropylene (Novatec EA9) were stored in three extruders, respectively.

  [3B] Next, these extruders were extruded in a molten state from three extruders. As a result, a laminated body in a molten state in which these forming materials were laminated in layers was obtained from the co-extruded T-die. Thereafter, the laminate was cooled to obtain a protective film of Example 1B.

(Examples 2B to 13B)
The type of polyolefin used in place of the homopolypropylene (Nobrene FS2011DG2) at 158 ° C. in the step [1B], the content of the elastomer contained in the adhesive layer forming material prepared in the step [1B], and the content of the elastomer in the step [3B] The protective films of Examples 2B to 13B were obtained in the same manner as in Example 1B, except that the average thickness of the pressure-sensitive adhesive layer in the formed laminate was changed as shown in Table 2.

2-3. Evaluation The protective film of each example was evaluated by the following method.

<1> Evaluation of Adhesion Strength Before Heat History First, for the protective film of each example, a resin substrate (manufactured by Sumitomo Bakelite Co., Ltd.) having a configuration in which a polarizer was sandwiched between two polycarbonate substrates (polycarbonate layers) was used. “P1352”) was prepared. Each protective film was pressure-bonded to both surfaces of each resin substrate using a roll under a load of 0.5 kg / cm ² , and the protective film was attached to obtain a laminate.

Then, the resulting laminate, the temperature 50 ° C., after storage under conditions of time 12hr, JIS C-6481: the peel strength was measured _{T 1} of the between the compliant polycarbonate substrate and the protective film 1996.

<2> Evaluation of adhesion strength after heat history First, for the protective films of the examples, a resin substrate (manufactured by Sumitomo Bakelite Co., Ltd.) having a configuration in which a polarizer was sandwiched between two polycarbonate substrates (polycarbonate layers) was used. “P1352”) was prepared. Each protective film was pressure-bonded to both surfaces of each resin substrate using a roll under a load of 0.5 kg / cm ² , and the protective film was attached to obtain a laminate.

Then, the resulting laminate, temperature 0.99 ° C., after storage under conditions of time 5min, JIS C-6481: the peel strength was measured _{T 2} of the between the compliant polycarbonate substrate and the protective film 1996.

  The evaluation results of the protective films of the examples obtained as described above are shown in Table 2 below.

As shown in Table 2, in the protective film in each example, since the polyolefin is contained in the adhesive layer, the peel strength T ₁ and the peel strength T ₂ are both 0.05 N / 25 mm or more and 3.0 N / 25 mm or less. Was set within the range. For this reason, when the protective film in each example is used, the punching and thermal bending of the resin substrate in the step [2] and the step [3] can be performed without peeling the protective film from the resin substrate. And, even if the protective film has passed through the heat history due to the thermal bending in the step [3], the protective film is formed so that the protective film can be separated from the resin substrate in the step [4]. It was found to be attached to.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to stick to a resin substrate without peeling at the time of the heat bending of a resin substrate, when peeling a protective film from a resin substrate after a heat bending, the adhesive residue derived from an adhesive layer A protective film capable of accurately suppressing or preventing the occurrence of on the resin substrate. Therefore, the present invention has industrial applicability.

DESCRIPTION OF SYMBOLS 10 Protective film 11 Adhesive layer 15 Base layer 16 1st layer 17 2nd layer 21 Resin substrate 23 Polarizer 24 Coating layer 30 Polycarbonate layer 100 Laminated body 200 Lens for sunglasses

Claims (8)

For a resin substrate, when subjected to thermal bending under heating, a protective film used to be attached to the resin substrate,
A base layer, and an adhesive layer that is located between the base layer and the resin substrate and adheres to the resin substrate,
A protective film, wherein the adhesive layer contains a polyolefin and a styrene block elastomer having a styrene content of 25% by weight or less.   The protective film according to claim 1, wherein the styrene block elastomer includes a styrene-olefin-styrene block copolymer.   The protective film according to claim 1, wherein the polyolefin has a melting point of 150 ° C. or higher.   The melt flow rate of the polyolefin measured at a heating temperature of 230 ° C. and a load of 2.16 kgf according to JIS K7210 is from 0.5 g / 10 min to 10.0 g / 10 min. The protective film according to any one of the above.   The protective film according to any one of claims 1 to 4, wherein the polyolefin includes a homopolymer of polypropylene.   The protective film according to any one of claims 1 to 5, which is attached to both surfaces of the resin substrate.   A coating layer comprising a single layer or a laminate having at least one of a polycarbonate resin layer, a polyamide resin layer and a cellulose resin layer is provided on both sides, one side or the other side of the resin substrate. Item 7. The protective film according to any one of Items 1 to 6.   The protective film according to any one of claims 1 to 7, wherein the resin substrate is subjected to the hot bending by press molding or vacuum molding.

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