EP-4741891-A2 - PROTECTIVE FILM, RESIN SUBSTRATE, LAMINATE OF PROTECTIVE FILM AND RESIN SUBSTRATE, RESIN SHEET LAMINATE, AND PROTECTIVE FILM SET

EP4741891A2EP 4741891 A2EP4741891 A2EP 4741891A2EP-4741891-A2

Abstract

A protective film 10 which is used by being attached to a resin substrate 21 in a case of performing heat bending on the resin substrate 21 while heating the resin substrate 21, the protective film comprising a base material layer and a pressure sensitive adhesive layer which is positioned between the base material layer and the resin substrate, and is adhered to the resin substrate,in which the base material layer is composed of a laminate including a first layer which is positioned on a side opposite to the pressure sensitive adhesive layer and a second layer which is positioned on a side of the pressure sensitive adhesive layer, and the pressure sensitive adhesive layer has a surface roughness Ra of 0.20 µm or less in a surface on a side of the resin substrate, which is measured in accordance with JIS B 0601.

Inventors

OYA, HIROSHI
MATSUI, TOMOKI
IZUMI, ATSUSHI

Assignees

Sumitomo Bakelite Co., Ltd.

Dates

Publication Date: 20260513
Application Date: 20220329

Claims (9)

A protective film which is used by being attached to a resin substrate in a case of performing heat bending on the resin substrate while heating the resin substrate, the protective film comprising: a base material layer; and a pressure sensitive adhesive layer which is positioned between the base material layer and the resin substrate, and is adhered to the resin substrate, wherein the base material layer is composed of a laminate including a first layer which is positioned on a side opposite to the pressure sensitive adhesive layer and a second layer which is positioned on a side of the pressure sensitive adhesive layer, and the pressure sensitive adhesive layer has a surface roughness Ra of 0.20 µm or less in a surface on a side of the resin substrate, which is measured in accordance with JIS B 0601.
The protective film according to claim 1, wherein the protective film has an elastic modulus at 25°C of 300 MPa or more and 600 MPa or less.
The protective film according to claim 1 or 2, wherein the first layer contains a thermoplastic resin as a main material and a melting point of the thermoplastic resin is 150°C or higher, the second layer contains a thermoplastic resin having adhesiveness as a main material and a melting point of the second layer is 120°C or higher, and the pressure sensitive adhesive layer contains a thermoplastic resin having pressure sensitive adhesiveness as a main material and a melting point of the thermoplastic resin is 110°C or lower
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 pressure sensitive adhesive layer contains, as a main material, a polyolefin-based resin having pressure sensitive adhesiveness.
The protective film according to any one of claims 1 to 5, wherein in a case where the protective film having a width of 25 mm and a length of 200 mm is attached to a polycarbonate substrate, and in an environment of 25°C, one end of the protective film is held and the protective film is peeled off in a direction of 90° to a position of a length of 100, and then the one end of the protective film is released to re-attach the protective film to the polycarbonate substrate, after 1 minute from the reattachment, a total area in a plan view of a region where the polycarbonate substrate and the protective film are not bonded to each other is less than 1250 mm 2 .
The protective film according to any one of claims 1 to 6, wherein the protective films are attached to both surfaces of the resin substrate.
The protective film according to any one of claims 1 to 7, wherein a coating layer, which is formed of a single layer or a laminate having at least one layer of a polycarbonate resin layer, a polyamide resin layer, and a cellulose resin layer, is provided on one surface or the other surface of the resin substrate, or the coating layers are provided on both surfaces of the resin substrate.
The protective film according to any one of claims 1 to 8, wherein the resin substrate is subjected to the heat bending by carrying out press molding or vacuum molding.

Description

Technical Field The present invention relates to a protective film which is used to be attached to a resin substrate in a case where the resin substrate is subjected to heat bending under heating, a resin substrate subjected to heat bending using such a protective film, a laminate of a protective film and a resin substrate in which such a protective film is attached to the resin substrate, a resin sheet laminate, and a protective film set. Background Art With regard to a lens for sunglasses provided with a resin substrate having a configuration in which both surfaces of a polarizer are coated with a coating layer formed of a polycarbonate resin, a polyamide resin, or a cellulose resin, for example, with protective films attached to both surfaces of the resin substrate, which has a flat plate shape in a plan view, the resin substrate is punched into a predetermined shape such as a circular shape in the plan view, and then the resin substrate is subjected to heat bending while being heated. Next, after peeling off the protective films from the heat-bent resin substrate, a polycarbonate layer is injection-molded on a concave surface of this resin substrate to manufacture the lens for sunglasses. As the protective film, for example, a protective film having a configuration in which a base material containing a polyolefin-based resin as a main material is attached to the resin substrate through a pressure sensitive adhesive layer containing, as a main material, polyethylene, an ethylene-propylene copolymer, and the like has been suggested (for example, see PTL 1). However, the protective film having such a configuration can be attached to the resin substrate without being peeled off in a case of punching the resin substrate and in a case of performing heat bending, but it has the following problems. That is, in a case of punching the resin substrate, in a cut surface which is formed by carrying out the punching, the pressure sensitive adhesive layer extends to the resin substrate side, which causes so-called whiskers. As a result, in a case where the protective film is peeled off from the resin substrate, the pressure sensitive adhesive layer remains as the whiskers on the cut surface of the resin substrate. Accordingly, there has been a problem that the yield of the lens for sunglasses to be manufactured is reduced. In addition, as described above, the protective films are attached to both surfaces of the resin substrate prior to punching the resin substrate, and this attachment is usually carried out using human hands, an arm provided with a machine tool, or the like. In the attachment of such a protective film, due to wrinkles in the protective film, air bubbles remaining between the protective film and the resin substrate, and the like, after at least part of the protective film is once peeled off from the resin substrate, in some cases, the peeled protective film may be re-attached (re-adhered) to the resin substrate. However, with the protective film configured as described above, after peeling off the protective film from the resin substrate, re-adhesion of the protective film to be re-attached to the resin substrate cannot be sufficiently obtained. Therefore, the current situation is that development of a protective film having excellent re-adhesion is demanded. In addition, in the protective film having such a configuration, the following problems may arise in a case where the protective film is peeled off from the resin substrate after the resin substrate is heat-bent. That is, in a case where the protective film is peeled off from the resin substrate after the heat bending of the resin substrate, a surface of the resin substrate, from which the protective film has been peeled off, is charged by static electricity caused by this peeling, and as a result, environmental foreign matter such as dust, scattered in the air, adheres to the surface of the resin substrate. Accordingly, there has been a problem that the yield of the lens for sunglasses to be manufactured is reduced. In addition, as described above, a plurality of processings such as the punching of the resin substrate and the heat bending of the resin substrate are applied to the resin substrate, and during these processings, the processings are carried out in a state in which the protective film is attached to the resin substrate, that is, a laminate is formed. During these processings, it is required that the protective film stably maintains the state in which the laminate is formed without peeling off the protective film from the resin substrate, but since conditions and the like in each processing are different, naturally, a degree of adhesive force required between the protective film and the resin substrate is also different. That is, the degree of adhesive force to the resin substrate, which is required for the protective film, varies depending on the varies types of processings, but as described above, the current situation is that there