JP3401110B2 - Surface protection film - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface protective film. 2. Description of the Related Art In a surface protective film, the properties of the adhesive layer are important depending on the type of the object to be protected, in addition to the physical properties of the entire film which governs the quality of the surface protective function. That is, the surface protection film attached at the time of manufacturing the protected object must be securely bonded so as not to be peeled off when the protected object is subjected to handling such as transportation, processing, and movement during storage. However, when the object to be protected is used, it is necessary that the surface protective film can be easily peeled off without causing contamination such as adhesive residue on the surface of the object to be protected. [0003] A synthetic resin plate such as a polycarbonate plate and an acrylic resin plate has a relatively small surface hardness and is easily damaged, and thus a surface protective film is adhered during production. At this time, as the surface protection film to be attached,
Although many proposals have been made, the one most commonly used in recent years has an adhesive layer made of an ethylene-vinyl acetate copolymer or a linear low-density polyethylene. Normally, when the surface protection film can be easily peeled off from the synthetic resin plate, the adhesive strength between them is 80 g /.
It is required that the width be 25 mm or less, preferably 50 g / 25 mm or less. However, the adhesive strength of the surface protective film attached to the surface of the object to be protected such as a synthetic resin plate increases with time (adhesion increases), and the temperature (particularly 100 ° C.)
The tendency is further accelerated by high energy irradiation such as high temperature, pressure, and ultraviolet rays. Therefore, even if the adhesive strength of the initial surface protection film attached to the surface of the protected object is appropriate, the adhesion has increased during use with time, and it has become difficult to peel off, or adhesive remains on the surface of the protected object. In many cases, it causes contamination such as cloudiness. When the object to be protected is processed by heating to a high temperature with the surface protective film adhered, the protective film increases in adhesion and becomes difficult to peel off. Therefore, in order to suppress this, the initial adhesive strength is set low. At the time of sticking the surface protective film or during the distribution process, the sticking property is poor or the film is naturally peeled off, and the function of the surface protective film cannot be fulfilled. For this reason, the initial adhesive strength of the surface protective film is 5 g / 2.
It is required that the width be 5 mm or more, preferably 10 g / 25 mm or more. As a surface protective film satisfying the above functions, for example, JP-A-3-47886 discloses that a pressure-sensitive adhesive is applied to a linear low-density polyethylene having a density of 0.900 to 0.920 g / cm ^3. A surface protective film excellent in heat resistance and UV resistance is disclosed in which an agent selected from the group consisting of hydrogenated terpene resin, terpene resin and terpene phenol resin is added in an amount of 0.1 to 5% by weight. I have. However, the tackifier used in the surface protection film described in the above-mentioned publication increases the adhesion by heating at a high temperature as described in the publication, so that the initial adhesion must be set low. Is not always good. [0008] The present invention has been made in view of the above facts, and has as its object
An object of the present invention is to provide an excellent surface protective film having excellent initial adhesiveness, little increase in adhesive strength even when subjected to a heat treatment, and less contamination of the surface of a protected object even in a high-temperature environment. . According to the present invention, a pentaerythritol ester resin of completely hydrogenated rosin and / or an aromatic modified terpene resin 0.3 to 4 is coated on one surface of a substrate film.
The gist of the present invention is a surface protection film on which an adhesive layer comprising a low-density polyethylene having a density of 0.918 to 0.924 g / cm ^{3 and} a low-density polyethylene of 99.7 to 96 weight% is formed. Although the substrate film used in the present invention is not particularly limited, for example, a film made of an olefin resin such as polyethylene or polypropylene is preferably used. Further, the base film may have only one layer, or may have two or more layers. Further, the base film is a light stabilizer, an antioxidant,
A stabilizer such as an ultraviolet absorber, a silane-based lubricant, a filler such as precipitated barium sulfate, talc, calcium carbonate, mica, and titanium oxide, a coloring agent, and the like may be added. When the density of the low-density polyethylene, which is the main component of the pressure-sensitive adhesive layer in the present invention, is less than 0.918 g / cm ³ , the material is heated to a high temperature, for example, when processing an object to be protected with the surface protective film attached. Then, when the surface protective film is peeled off, contamination such as adhesive residue and fogging is given to the surface of the protected object, and when it exceeds 0.924 g / cm ³ , the surface of the pressure-sensitive adhesive layer tends to be rough and the initial adhesive strength tends to be reduced. The density of the low-density polyethylene in the present invention is determined according to JIS K 6760 “Testing method for polyethylene”.
5.2 measured according to specific gravity and density. The tackifier, which is another component of the pressure-sensitive adhesive layer in the present invention, has good compatibility with the above low-density polyethylene, and has a good process-following property when processing a material to be protected while the surface protective film is adhered. Good fully hydrogenated rosin pentaerythritol ester resin and / or aromatic modified terpene resin. The pentaerythritol ester resin of completely hydrogenated rosin is one of the pentaerythritol ester of tetrahydroabietic acid listed as a main component of hydrogenated rosin on page 101 of "Adhesion Handbook" published by Industrial Adhesive Tape Industry Association. Commercial products include "Foral 105" (trade name, manufactured by Rika Hercule Co., Ltd.). [0015] The aromatic modified terpene resin is, as described in the “Adhesion Handbook”, page 105,
It is obtained by copolymerization of an aromatic monomer and a terpene monomer, and commercially available products include "TR-105" (trade name, manufactured by Yasuhara Chemical Co., Ltd.). The completely hydrogenated rosin pentaerythritol ester resin and the aromatic modified terpene resin may be added to the low-density polyethylene alone or in combination. When the amount of the tackifier is less than 0.3% by weight, the initial adhesive strength and the adhesive force when a processing involving heating is performed are reduced. Adhesion afterwards increases, and neither is preferable. The thickness of the surface protective film of the present invention is not particularly limited as long as it has a function of protecting the object to be protected from scratches, dirt and the like. , 10-30 μm, the thickness of the substrate layer is 30-70 μm
m, and those having a total thickness of about 40 to 100 μm are preferable. In the surface protective film of the present invention, the base film and the adhesive layer are individually formed to a predetermined thickness by a forming method such as a T-die method or an inflation method. A method in which the layers are integrated by thermal lamination, a method in which an adhesive layer is provided on a base film by an extrusion lamination method, or a method in which the base film and the adhesive layer are simultaneously subjected to multilayer extrusion such as a T-die method or an inflation method. It is obtained by a method of molding to a predetermined thickness by the method. The surface protective film for a resin plate of the present invention has a modified aromatic terpene resin and / or a completely hydrogenated rosin pentaerythritol ester resin on one surface of a substrate film.
3-4% by weight and density 0.918-0.924 g / cm ³
Of the low-density polyethylene of 99.7 to 96% by weight, the adhesion does not increase when heated at a high temperature, and the adhesion decreases when heated at a high temperature. It can be set high, has excellent initial adhesiveness, has little increase in adhesive strength even when subjected to heat treatment, and has little contamination of the surface of the protected object even when placed in a high-temperature environment. Hereinafter, embodiments of the present invention will be described in detail. Example 1 Low-density polyethylene having a density of 0.918 g / cm ³ (trade name: L-70, manufactured by Sumitomo Chemical Co., Ltd.)
5) An adhesive layer composed of 99.7% by weight and 0.3% by weight of a completely hydrogenated rosin pentaerythritol ester resin (manufactured by Rika Hercule, trade name: Foral 105) and high-density polyethylene (manufactured by Asahi Kasei Corporation, trade name) : S-360, density 0.960 g / cm ³ ), which was co-extruded by an inflation method to produce a surface protective film having a thickness of 20 μm for the adhesive layer and a thickness of 40 μm for the substrate layer. Example 2 Low-density polyethylene having a density of 0.924 g / cm ³ (trade name: CY44, manufactured by Sumitomo Chemical Co., Ltd.)
3) The thickness of the pressure-sensitive adhesive layer was changed in the same manner as in Example 1 except that the pressure-sensitive adhesive layer was changed to 96% by weight and 4% by weight of an aromatic modified terpene resin (trade name: "TR-105" manufactured by Yasuhara Chemical Co., Ltd.). A surface protection film having a thickness of 20 μm and a thickness of the substrate layer of 40 μm was prepared. Comparative Example 1 Low-density polyethylene 99.8
In the same manner as in Example 1, except that the pressure-sensitive adhesive layer was composed of 0.2% by weight of pentaerythritol ester resin of completely hydrogenated rosin and 20% by weight of the pressure-sensitive adhesive layer and 40 μm in thickness of the base material layer. A surface protection film was produced. Comparative Example 2 The thickness of the adhesive layer was changed in the same manner as in Example 1 except that the adhesive layer was composed of 95% by weight of low-density polyethylene and 5% by weight of a completely hydrogenated rosin pentaerythritol ester resin. A surface protection film having a thickness of 20 μm and a thickness of the substrate layer of 40 μm was prepared. Comparative Example 3 99% by weight of a linear low-density polyethylene having a density of 0.910 g / cm ³ (manufactured by Mitsui Petrochemical Co., trade name: 1020L) and a hydrogenated terpene resin (manufactured by Yashara Chemical Co., trade name: Clearon P125) The thickness of the adhesive layer was 20 μm and the thickness of the base material layer was 40 μ in the same manner as in Example 1, except that the adhesive layer was changed to 1% by weight.
m of the surface protective film was prepared. Performance Test The surface protection films obtained in the above Examples and Comparative Examples were measured for the following items by the following test methods. Table 1 shows the test results. 1. Initial adhesive strength: A surface protective film was stuck on an acrylic plate having a thickness of 2 mm with a laminator, and left in an environment of a temperature of 23 ° C. and a humidity of 65% RH for 30 minutes. The adhesion was measured. 2. Evaluation of adhesion enhancement: A surface protective film was stuck on an acrylic plate having a thickness of 2 mm with a laminator, and in a hot air circulating oven, 120 ° C. × 1 hour, 150 ° C. × 3.
After heating at 0 ° C for 3 minutes at 180 ° C for 10 minutes, the mixture was allowed to cool to room temperature, then left at 23 ° C for 30 minutes, and then peeled off width 2
180 degree peel strength was measured at 5 mm, and the adhesion enhancement property was evaluated. 3. Contamination evaluation: The surface protection film was peeled off from the sample for evaluation of adhesion enhancement described in the preceding paragraph, and the presence or absence of glue residue and fogging on the acrylic plate surface was visually observed and evaluated under UV light. Table 1 shows the results. [Table 1] As is clear from Table 1, each of the surface protective films of Examples 1 and 2 of the present invention has a sufficient initial adhesive force to the acrylic resin plate, and the surface of each of the above-mentioned protected objects. Even if the heat treatment is performed in a state where the surface protective film is adhered, the adhesive strength does not increase but rather decreases, and the surface protective film can be easily peeled off from the surface of the protected object after use. Further, even after peeling, there is no contamination such as cloud or glue residue on the surface of the protected object. On the other hand, in Comparative Example 1, both the initial adhesive strength and the adhesive strength after the heat treatment are low, the sticking property is poor, and there is a possibility that the adhesive will spontaneously peel off in the course of distribution, processing and the like. In Comparative Example 2, both the initial adhesive strength and the adhesive strength after the heat treatment were high, and peeling was difficult. In Comparative Example 3, the adhesion was slightly increased, and the surface of the protected object was contaminated with adhesive residue and fogging. Since the surface protective film of the present invention is constituted as described above, the adhesion does not increase when heated at a high temperature, and the adhesion decreases when heated at a high temperature. It can be set high, has excellent initial adhesiveness, has little increase in adhesive strength even when subjected to heat treatment, and has little contamination of the surface of the protected object even when placed in a high-temperature environment.

Claims (1)

(57) [Claim 1] 0.3 to 4% by weight of a fully hydrogenated rosin pentaerythritol ester resin and / or an aromatic modified terpene resin and a density of 0.918 on one surface of a base film. ~
0.924 g / cm ³ low density polyethylene 99.7-
A surface protective film on which an adhesive layer consisting of 96% by weight is formed.