JP2022159186A - Protective film, resin substrate and protective film-resin substrate laminate - Google Patents

Abstract

To provide a protective film which can accurately suppress or prevent an environment foreign matter from adhering to a surface of a resin substrate when the resin substrate is thermally bent, and then the protective film is peeled from the resin substrate, a resin substrate which is thermally bent using the protective film, and a protective film-resin substrate laminate in which the protective film is stuck to the resin substrate.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 protective film 10 is configured that the surface on the resin substrate 21 side of the adhesive layer is negatively charged due to peeling from the resin substrate 21, and thereby the surface on the adhesive layer side of the resin substrate 21 is positively charged.SELECTED DRAWING: Figure 1

Description

The present invention provides a protective film that is attached to a resin substrate when the resin substrate is subjected to thermal bending under heating, a resin substrate that is subjected to thermal bending using such a protective film, and such protection. The present invention relates to a protective film/resin substrate laminate in which a film is attached to a resin substrate.

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).

However, in the protective film having such a configuration, the following problems may occur when the protective film is peeled off from the resin substrate after the resin substrate is thermally bent. That is, when the protective film is peeled off from the resin substrate after thermal bending of the resin substrate, the surface of the resin substrate from which the protective film is peeled is charged due to static electricity caused by the peeling, and as a result, Environmental foreign matter such as dust scattered in the air adheres to the surface of the resin substrate. Therefore, there is a problem that the yield of manufactured sunglasses lenses is lowered.

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

An object of the present invention is to provide a protective film that can accurately suppress or prevent environmental foreign substances from adhering to the surface of a resin substrate when it is peeled off from the resin substrate after thermal bending of the resin substrate. An object of the present invention is to provide a resin substrate that is subjected to thermal bending using a film, and a protective film/resin substrate laminate in which the protective film is attached to the resin substrate.

Such objects are achieved by the present invention described in (1) to (10) below.
(1) A protective film that is attached to a resin substrate when the resin substrate is subjected to thermal bending under heating, and is peeled off from the resin substrate after the thermal bending,
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,
When the protective film is peeled off from the resin substrate, the surface of the adhesive layer on the resin substrate side is negatively charged, thereby positively charging the surface of the adhesive layer on the resin substrate. A protective film characterized by comprising:

(2) The protective film according to (1) above, wherein the surface of the adhesive layer on the second layer side is positively charged by peeling from the resin substrate.

(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, which is of

(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 are both polyolefins.

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

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

(7) 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 (6) above.

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

(9) A resin substrate to which a thermal bending process is applied under heating with a protective film attached,
The resin substrate is subjected to thermal bending with the protective film attached when the thermal bending is performed, and the protective film is peeled off from the resin substrate after the thermal bending. ,
The protective film includes a base layer and
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 resin substrate is such that the surface of the adhesive layer on the resin substrate side is positively charged due to the negative charging of the surface of the adhesive layer on the resin substrate side due to the peeling of the protective film. A resin substrate characterized by:

(10) A protective film/resin substrate laminate formed when the resin substrate is thermally bent with the protective film attached to the resin substrate,
When the resin substrate is subjected to the thermal bending process, the thermal bending process is performed with the protective film attached thereto, and the protective film is peeled off from the resin substrate after the thermal bending process. ,
The protective film includes a base layer and
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,
In the protective film/resin substrate laminate, when the protective film is peeled off from the resin substrate, the surface of the adhesive layer on the resin substrate side is negatively charged, and due to the negative charging, A protective film/resin substrate laminate, wherein the surface of the resin substrate on the side of the adhesive layer is positively charged.

According to the present invention, when the protective film is peeled off from the resin substrate, the surface of the adhesive layer on the resin substrate side is negatively charged, thereby positively charging the surface of the adhesive layer on the resin substrate. It is configured. Here, most of the environmental contaminants such as dust scattered in the air are generally positively charged. Therefore, as in the present invention, when the protective film is peeled off from the resin substrate, the surface of the adhesive layer side of the resin substrate is positively charged by the static electricity generated due to this peeling, so that the environmental foreign matter and A repulsive force acts between it and the resin substrate. Therefore, it is possible to accurately suppress or prevent environmental foreign matter from adhering to the surface of the resin substrate from which the protective film has been peeled off. Therefore, when the resin substrate is applied to, for example, a resin substrate included in a lens for sunglasses, the lens for sunglasses can be manufactured with a high yield.

It is a schematic diagram for demonstrating the manufacturing method of the lens for sunglasses using a protective film. 1 is a vertical cross-sectional view showing a preferred embodiment of a protective film of the present invention; FIG. 3 is a longitudinal sectional view for explaining a state in which the protective film shown in FIG. 2 is peeled off from the resin substrate; 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 addition, the main material in this specification refers to a constituent material contained in each film (each layer) in an amount of 50% by weight or more. "Contains.", When the total weight of the first layer is 100% by weight, the thermoplastic resin contained in the first layer occupies 50% by weight or more in the first layer 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 When the protective film is peeled off from the resin substrate, the surface of the adhesive layer on the resin substrate side is negatively charged, and as a result, the surface of the resin substrate is negatively charged. The adhesive layer side surface is configured to be positively charged.

Thus, in the present invention, the surface of the adhesive layer on the resin substrate side is negatively charged by peeling the protective film from the resin substrate, thereby positively charging the surface of the adhesive layer on the resin substrate. is configured as follows. Here, most of the environmental contaminants such as dust scattered in the air are generally positively charged. Therefore, as described above, when the protective film is peeled off from the resin substrate, static electricity generated due to this peeling causes the surface of the adhesive layer side of the resin substrate to be positively charged, thereby separating the environmental contaminants from the resin substrate. A repulsive force acts between it and the substrate. Therefore, it is possible to accurately suppress or prevent environmental foreign matter from adhering to the surface of the resin substrate from which the protective film has been peeled off. Therefore, when the resin substrate is applied to, for example, a resin substrate included in a lens for sunglasses, the lens for sunglasses can be manufactured with a high yield.

Prior to describing the protective film, the resin substrate, and the protective film/resin substrate laminate of the present invention, a method for manufacturing sunglasses lenses 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 for manufacturing a sunglass lens using a protective film. For convenience of explanation, the upper side of FIG. 1 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 (protective film/resin substrate laminate) 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 method for manufacturing a lens for sunglasses as described above, particularly when the protective film 10 is peeled off from the thermally bent resin substrate 21 in the step [4], the peeling causes The generated static electricity charges the surface of the resin substrate 21 from which the protective film 10 has been removed. As a result, environmental foreign matter such as dust scattered in the air is also charged in the air, so that the environmental foreign matter adheres to the surface of the resin substrate 21 .

Therefore, in this state, if the polycarbonate layer 30 is formed on the resin substrate 21 to manufacture the sunglasses lens 200 in the step [4], there is a problem that the yield of the sunglasses lens 200 is lowered.

As a result of investigations by the present inventors regarding this problem, the environmental foreign substances adhering to the surface of the resin substrate 21 are mainly composed of dust originating from the fibers that constitute the cloth portion of clothing and the like. Environmental contaminants are generally predominantly positively charged. It has been found that the surface of the resin substrate 21 is negatively charged due to static electricity generated when the protective film 10 is peeled off from the resin substrate 21, on which environmental foreign matter is observed to adhere. rice field.

In response to such a situation, in the present invention, in the step [4], the protective film 10 (protective film of the present invention) is replaced with the resin substrate in the laminate 100 (protective film/resin substrate laminate of the present invention). 21, the surface of the adhesive layer 11 on the side of the resin substrate 21 is negatively charged (negatively charged) due to static electricity generated by this peeling. It is configured to positively charge (positively charge) the surface of (the resin substrate of the present invention) on the side of the adhesive layer 11 .

Thus, in the present invention, the surface of the adhesive layer 11 side of the resin substrate 21 is intentionally charged positively, so that the surface of the resin substrate 21 on the adhesive layer 11 side is also positively charged. A repulsive force can be applied to the environment foreign matter. Therefore, it is possible to accurately suppress or prevent environmental foreign matter from adhering to the surface of the resin substrate 21 from which the protective film 10 has been peeled off.

By intentionally charging the surface of the adhesive layer 11 side of the resin substrate 21 with a positive charge in this way, the protective film 10 is peeled off from the resin substrate 21 that has been thermally bent in the step [4]. It is possible to accurately suppress or prevent environmental foreign matter from adhering to the surface of the resin substrate 21 when the resin substrate 21 is exposed. 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, but the resin material used in the present invention is not limited to the description below. By changing the charging state of the protective film and adjusting the charging amount of the resin substrate after the protective film is peeled off, it is also possible to accurately suppress or prevent the adhesion of environmental foreign matter.

<Protective film 10>
FIG. 2 is a longitudinal sectional view showing a preferred embodiment of the protective film of the present invention, and FIG. 3 is a longitudinal sectional view for explaining a state in which the protective film shown in FIG. 2 is separated from the resin substrate. For convenience of explanation, the upper side of FIGS. 2 and 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 .

The adhesive layer 11 has a configuration in which a polyolefin resin alone is contained in the adhesive layer 11 as a thermoplastic resin, or a configuration in which a polyolefin resin and an elastomer are combined in the adhesive layer 11. is preferred. The function of the adhesive layer 11 can be reliably exhibited by using the adhesive layer 11 having a structure containing such a thermoplastic resin.

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. 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 attaching the protective film 10 to the resin substrate 21 in step [1], it is possible to visually check whether or not dust such as dust is interposed between the protective film 10 and the resin substrate 21. Since it is possible to reliably prevent the layered body 100 containing dust from moving after 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. copolymer (SBS), styrene-isoprene-styrene copolymer (SIS), styrene-ethylene-propylene-styrene block copolymer (SEPS), among others, styrene-ethylene-butylene-styrene block copolymer It is preferably a polymer (SEBS). 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 2% by weight or more and 60% by weight or less, more preferably 4% by weight or more and 40% 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.

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.

In this specification, the melting point of each layer constituting the protective film 10 including the first layer 16 refers to the melting point (peak temperature by DSC measurement) of each constituent material contained in each layer. Let the melting point be the sum of the products multiplied by the contained ratios.

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 attaching the protective film 10 to the resin substrate 21 in step [1], it is possible to visually check whether or not dust such as dust is interposed between the protective film 10 and the resin substrate 21. Since it is possible to reliably prevent the layered body 100 containing dust from moving after 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.

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, when the second layer 17 contains an elastomer, the content of the elastomer in the second layer 17 is not particularly limited, but is preferably 0.5% by weight or more and 40% by weight or less, more preferably 1% by weight. % or more and 25% by weight or less. As a result, the effect obtained by including the elastomer in the second layer 17 can be exhibited more remarkably.

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 attaching the protective film 10 to the resin substrate 21 in step [1], it is possible to visually check whether or not dust such as dust is interposed between the protective film 10 and the resin substrate 21. Since it is possible to reliably prevent the layered body 100 containing dust from moving after 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 substrate layer 15 having the first layer 16 and the second layer 17 having the above-described structure is separated from the resin substrate 21 as described above. The surface of the adhesive layer 11 on the resin substrate 21 side is negatively charged (negatively charged), thereby positively charging the surface of the resin substrate 21 on the adhesive layer 11 side (see FIG. 3). .

In this way, from the state in which the protective film 10 is attached to the resin substrate 21 as shown in FIG. The electrification series in each layer of the protective film 10 including the adhesive layer 11 and the base layer 15 having the first layer 16 and the second layer 17 is adjusted so that the surface on the resin substrate 21 side is negatively charged. be done.

That is, by peeling the protective film 10 from the resin substrate 21, specifically, the surface of the adhesive layer 11 on the side of the second layer 17 is positively charged, and the second layer 17 is on the adhesive layer 11 side. is negatively charged, the surface on the first layer 16 side is positively charged, the first layer 16 is negatively charged on the second layer 17 side, and the second layer The electrification series of each layer is adjusted so that the surface opposite to 17 is positively charged. Then, the combination of constituent materials contained in each layer of the adhesive layer 11, the first layer 16, and the second layer 17 is adjusted so as to realize this electrification series.

Specifically, the combination of constituent materials contained in each layer of the adhesive layer 11, the first layer 16, and the second layer 17 is not particularly limited, but for example, the following combinations are possible. mentioned. That is, a combination of LLDPE contained in the adhesive layer 11, h-PP contained in the first layer 16, h-PP and SEPS contained in the second layer 17, LLDPE contained in the adhesive layer 11, The combination of the h-PP contained in the first layer 16 and the h-PP and SEBS contained in the second layer 17, and the LLDPE contained in the adhesive layer 11 and the h contained in the first layer 16 A combination of -PP and b-PP included in the second layer 17, and the like. By combining the constituent materials contained in each layer as described above, the protective film 10 as a whole is negatively charged by peeling the protective film 10 from the resin substrate 21 shown in FIG. , the surface of the adhesive layer 11 on the resin substrate 21 side is negatively charged (negatively charged). Then, the surface of the adhesive layer 11 on the resin substrate 21 side is charged with negative charges, so that the surface of the adhesive layer 11 side of the resin substrate 21 is positively charged.

Regarding the method of changing the charged state of the protective film 10 by applying an external force such as friction, for example, by rubbing on the protective film 10 provided in the laminate 100 with nylon, rayon, silk, glass rod, etc., after peeling can adjust the charge amount of the resin substrate 21.

The charge amount of the resin substrate 21 after the protective film 10 is peeled off is preferably 10.0 kV or less, more preferably 6.5 kV or less. Such adjustment can appropriately prevent environmental foreign matter from adhering to the surface of the resin substrate 21 from which the protective film 10 has been peeled off.

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, etc. may be included.

In particular, the first layer 16 preferably contains an anti-blocking agent whose content is set to preferably 0.5% by weight or more and 10% by weight or less, more preferably 1% by weight or more and 9% by weight or less. be provided. As a result, the function obtained by providing the first layer 16 functioning as a protective layer as the back layer (outermost layer) can be exhibited more remarkably.

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.

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 .

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, 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 comparative example are as follows.

<<Thermoplastic resin having non-adhesiveness>>
<Polyolefin-based resin having a melting point of 150°C or higher>
Homo polypropylene with a melting point of 158° C. (h-PP, manufactured by Sumitomo Chemical Co., Ltd., "Noblen FS2011DG2", MFR = 2.5 g/10 min)

<Polyolefin resin having a melting point of 120°C or more and less than 150°C>
Linear low-density polyethylene (LLDPE, Prime Polymer Co., Ltd., "Neozex 2015M", MFR = 1.2 g/10 min) with a melting point of 121 ° C.

<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)

<<Thermoplastic resin having adhesiveness>>
<Elastomer>
Styrene-ethylene-butylene-styrene block copolymer (SEBS, manufactured by Asahi Kasei Corporation, "Tuftec H1221")
Styrene-ethylene-propylene-styrene block copolymer (SEPS, manufactured by Kuraray Co., Ltd., "Hybler 7125")

<Polyolefin resin>
Block polypropylene (propylene-ethylene block copolymer) having a melting point of 165° C. (b-PP, manufactured by Sumitomo Chemical Co., Ltd., “Noblen KS23F8”, MFR=2.1 g/10 min)

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

2. Production of protective film (Example 1)
[1] First, in forming an adhesive layer (innermost layer), LLDPE having a melting point of 114° C. was prepared as an adhesive layer-forming material (resin composition) as a polyolefin resin.

[2] Next, in forming the second layer (intermediate layer) included in the base material layer, SEPS as a thermoplastic resin having adhesiveness and h having a melting point of 158 ° C. -PP was kneaded so that the content of SEPS was 30% by weight to prepare a second layer-forming material (resin composition).

[3] Next, an adhesive layer-forming material, a second layer-forming material prepared, and a polyolefin resin having a melting point of 150°C or higher for forming the first layer (outermost layer), which has a melting point of 158°C. of h-PP were each housed in three extruders.

[4] Next, by extruding these in a molten state from three extruders, a molten laminate in which these are laminated in layers is obtained from a co-extrusion T die. was cooled to obtain the protective film of Example 1 in which the average thicknesses of the first layer, the second layer and the adhesive layer were 10 μm, 30 μm and 10 μm, respectively.

(Examples 2 to 13, Comparative Example 1)
The type of polyolefin resin and the type of elastomer used in the step [1], the type of the adhesive thermoplastic resin, the non-adhesive thermoplastic resin used in the step [2], the anti The presence or absence of a blocking agent, the content of the adhesive thermoplastic resin contained in the second layer-forming material to be prepared, and the first layer, the second layer, and the Protection of Examples 2 to 11 and Comparative Example 1 in the same manner as in Example 1 except that at least one of the average thicknesses of the adhesive layers was changed as shown in Table 1. got the film.

3. Evaluation The protective films of Examples and Comparative Examples were evaluated by the following methods.

<1> Electrification property on resin substrate due to peeling of protective film (manufactured by Bakelite Co., Ltd.) was pressed with a roll under a load of 0.5 kg/cm ² to obtain a laminate in which protective films were attached to both sides of the resin substrate.

The polycarbonate constituting the resin substrate is an aromatic polycarbonate resin obtained by an interfacial polycondensation reaction between bisphenol A and phosgene, and after being sheeted by extrusion molding, a mirror surface is formed by mold transfer. .

Then, the resin substrate having the protective films attached on both sides thereof was punched out in the thickness direction, so that the laminated body was formed into a circular shape in a plan view.
The area of the resulting circular laminate was about 4,400 mm ² .

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. Here, in Example 13, after the thermal bending process, friction was applied with nylon under predetermined conditions from above the protective film provided in the laminate.

Next, after holding the laminate under conditions of 25° C. for 30 minutes, holding one end of the protective film on one side in an environment of 25° C., the protective film was quickly peeled off from the resin substrate within 1 second. .

Then, in the protective film peeled from the resin substrate, the presence or absence of electrification of the entire protective film and the presence or absence of electrification on the surface of the adhesive layer on the resin substrate side were measured with a static meter (manufactured by SIMCO, "FMX-004 ”) within 2 seconds after peeling. In addition, in the resin substrate from which the protective film has been peeled off, the presence or absence and amount of charge on the surface of the adhesive layer side of the resin substrate is measured using a static meter (manufactured by SIMCO, "FMX-004"). Measured within 2 seconds.

Furthermore, one minute after the protective film was peeled off and left in the atmosphere, the surface of the adhesive layer side of the resin substrate was visually observed for the presence or absence of adhesion of environmental foreign matter (dust), and adhesion of environmental foreign matter was observed. It was evaluated as ⊚ when there was no environmental foreign matter, ∘ when some environmental foreign matter was observed, and x when the environmental foreign matter was clearly observed.

<2> Evaluation of whether or not whiskers adhere to resin substrates (manufactured by 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 presence or absence of formation of orange peel on the surface of the resin substrate A laminated body was obtained by attaching a protective film to both surfaces of a substrate (manufactured by Sumitomo Bakelite Co., Ltd.) by pressure bonding using a roll 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.

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

As shown in Table 1, in the protective film in each example, when the protective film was peeled off from the resin substrate, the surface of the adhesive layer on the resin substrate side was negatively charged. surface can be positively charged, and as a result, adhesion of environmental foreign matter (dust) to the resin substrate can be effectively suppressed or prevented.

On the other hand, in the protective film in the comparative example, the surface of the adhesive layer on the resin substrate side is positively charged due to the peeling of the protective film from the resin substrate. was negatively charged, resulting in unintentional adhesion of environmental foreign matter (dust) 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 (10)

A protective film that is attached to a resin substrate when the resin substrate is subjected to thermal bending under heating and is peeled off from the resin substrate after the thermal bending,
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,
When the protective film is peeled off from the resin substrate, the surface of the adhesive layer on the resin substrate side is negatively charged, so that the surface of the adhesive layer on the adhesive layer side of the resin substrate is positively charged. A protective film characterized by comprising: 2. The protective film according to claim 1, wherein the surface of the adhesive layer on the second layer side is positively charged when the protective film is peeled off from the resin substrate. 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. A protective film according to claim 1 or 2. 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 are polyolefins. The protective film according to any one of claims 1 to 4, wherein the adhesive layer contains polyolefin having adhesiveness as a main material. 6. The protective film according to any one of claims 1 to 5, 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 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 thermal bending process by press molding or vacuum molding. A resin substrate that is subjected to thermal bending under heating with a protective film attached,
The resin substrate is subjected to thermal bending with the protective film attached when the thermal bending is performed, and the protective film is peeled off from the resin substrate after the thermal bending. ,
The protective film includes a base layer and
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 resin substrate is such that the surface of the adhesive layer on the resin substrate side is positively charged due to the negative charging of the surface of the adhesive layer on the resin substrate side due to the peeling of the protective film. A resin substrate characterized by: A protective film/resin substrate laminate formed when the resin substrate is thermally bent with the protective film attached to the resin substrate,
When the resin substrate is subjected to the thermal bending process, the thermal bending process is performed with the protective film attached thereto, and the protective film is peeled off from the resin substrate after the thermal bending process. ,
The protective film includes a base layer and
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,
In the protective film/resin substrate laminate, when the protective film is peeled off from the resin substrate, the surface of the adhesive layer on the resin substrate side is negatively charged, and due to the negative charging, A protective film/resin substrate laminate, wherein the surface of the resin substrate on the side of the adhesive layer is positively charged.

Images