JP2005028618A - Manufacturing method of surface protective film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyethylene-based surface protective film which is temporarily bonded to the surface of each of a resin film for an optical product, a resin sheet, a resin panel and the like to protect the surface thereof and has an effect for preventing the blocking of them when they are taken up in a roll form or stacked, and its manufacturing method. <P>SOLUTION: In the manufacturing method of the polyethylene surface protective film by taking up a molten polyethylene film comprising a single layer or two or more layers extruded in a molten state from a T-die, the molten polyethylene film extruded from the T-die is held between a mirror surface cooling roll of which the surface roughness is a ten point height of irregularities Rz of 0.5 μm or below and a press roll having a rubber surface. The manufacturing method of the polyethylene surface protective film is also disclosed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention temporarily attaches to the surface of a resin film for optical products, a resin sheet or a resin plate, and protects these surfaces and prevents them from being blocked when rolled up or stacked. It is related with the polyethylene-type surface protection film which has the effect to do, and its manufacturing method.
[0002]
[Prior art]
Conventional surface protection films are used to prevent the introduction of foreign materials during the transportation, storage, and processing of resin plates, metal plates, etc. (hereinafter referred to as adherends) and to prevent the surface from being damaged. When the adherend is used as a product, it is used and peeled off. Therefore, the surface protective film is required to have adhesion or adhesiveness with the adherend, and when peeled, the surface protective film component is required not to adhere to the adherend.
[0003]
In recent years, progress has been made in the development of optical products such as liquid crystal substrate glass, polarizing films for liquid crystal displays, thin display device films, retardation films, light diffusion sheets, optical disc components such as DVDs, and precision fine-coated face plates for electronic and optical applications. is doing. Many of these optical products have very precise structure control, and are very sensitive to scratches and foreign matters. Further, for example, when the optical film is rolled up, there is a problem that the optical film itself causes blocking. Accordingly, there is a need for a surface protective film that protects the surface for these optical products and at the same time prevents blocking.
Furthermore, from the viewpoint of environmental problems, it is preferable that a large amount of the peeled surface protective film is reused in some form, and a surface protective film composed of a single resin is required.
[0004]
Conventionally, a polyethylene-based surface protective film is well known. As one example, a surface protective film is known in which a mixture of an ethylene-vinyl acetate copolymer (EVA) and a specific polyethylene resin is laminated on one side of a base material layer made of a thermoplastic resin, It is disclosed that the problem of increase in adhesive force due to heating is solved, and problems such as dents in protected objects and entrainment of bubbles due to the generation of fish eyes are not caused (for example, see Patent Document 1).
[0005]
In addition, the surface protective film made of a composition of a specific ethylene / α-olefin copolymer and low-density polyethylene or high-density polyethylene is excellent in adhesiveness, has little contamination to the article to be protected, and is also transparent. It is disclosed that it is excellent (for example, refer to Patent Document 2).
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-132864 [Patent Document 2]
Japanese Patent Laid-Open No. 11-228755
[Problems to be solved by the invention]
However, with the above surface protective film, it is difficult to satisfy the aforementioned requirements for antiblocking and recyclability. That is, it is difficult to recycle as a single resin using an ethylene-vinyl acetate copolymer and a specific polyethylene resin, and the ethylene-vinyl acetate copolymer tends to generate residual deposits. There is a point. In addition, there is no disclosure of an anti-blocking effect in a surface protective film comprising a composition of a specific ethylene / α-olefin copolymer and low density polyethylene or high density polyethylene.
[0008]
The present invention is limited to polyethylene as a resin so that recycling after use is possible, a polyethylene surface protective film that satisfies adhesion or adhesion to an adherend and prevents blocking of the adherend, and its An object is to provide a manufacturing method.
[0009]
[Means for Solving the Problems]
The present inventors are all made of polyethylene, and can be bonded to an adherend, and after being bonded to the adherend, they are not blocked even when wound into a roll film or stacked. As a result of intensive studies as a means for providing a polyethylene surface protective film, the present inventors have found that this object can be achieved in a resin that satisfies certain conditions and processing conditions. That is, the present invention is as follows.
[0010]
(1) In a method for producing a polyethylene surface protective film for winding a polyethylene melt film composed of a single layer or two or more layers melt-extruded from a T die, the surface of a cooling roll after the polyethylene melt film is extruded from the T die A method for producing a polyethylene surface protective film, characterized in that the surface roughness is sandwiched between a mirror surface cooling roll having a 10-point average roughness Rz of 0.5 μm or less and a pressing roll whose surface is rubber.
[0011]
(2) The polyethylene constituting the layer of the polyethylene melt film that contacts the cooling roll is low density polyethylene having a swell ratio of 1.45 or less, and the melt film is extruded from the T die at a temperature of 270 ° C. or more. (1) The manufacturing method of the polyethylene surface protection film as described in (1) characterized by these.
[0012]
(3) A polyethylene surface protective film obtained by the method of (1) or (2). Hereinafter, the present invention will be described in detail.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The polyethylene surface protective film of the present invention is composed entirely of polyethylene as a resin component, and can be recovered as a polyethylene resin after use and reused for applications in which a recycled resin can be used.
[0014]
As the polyethylene resin used in the present invention, low density polyethylene, linear low density polyethylene, ultra-low density polyethylene, high density polyethylene, medium density polyethylene and the like can be used.
[0015]
Among them, as the polyethylene resin constituting the layer in contact with the cooling roll, it is possible to use low-density polyethylene having a swell ratio of 1.45 or less, adhesion to the adherend, and residue on the adherend after peeling. This is particularly preferable. In the case of using low density polyethylene having a swell ratio of 1.45 or less, it is preferable to perform melt extrusion from a T die at a temperature of 270 ° C. or higher because adhesion with an adherend is increased. Although there is no restriction | limiting in particular about the upper limit of temperature, If it is too high, it will become easy to generate | occur | produce a fish eye and a burn, and it is preferable that it is 320 degrees C or less.
[0016]
The polyethylene surface protective film of the present invention has a mirror surface cooling roll having a 10-point average roughness of 0.5 μm or less and a rubber surface on the surface after the polyethylene melt film is extruded from the T-die. It is sandwiched between rolls.
The ten-point average roughness is defined in JIS B0601-1994.
[0017]
When the surface roughness of the cooling roll exceeds 0.5 μm in terms of 10-point average roughness, the smoothness of the bonding surface to the adherend is poor, and the bonding to the adherend tends to be insufficient.
[0018]
In the present invention, it is essential that the molten film is not only cooled by the cooling roll but also simultaneously pressed by the pressing roll. If it is not pressed with a pressing roll, the film surface on the side opposite to the cooling roll will also exhibit a certain degree of tackiness or adhesion, so that it is blocked when it is wound or stacked after being attached to an adherend.
[0019]
If the surface of the pressing roll is rubber, the film surface becomes polished glass, there is no adhesion to the adherend, it is possible to prevent blocking, and the film becomes slippery even when processing the surface protection film It becomes easy to wind up neatly. Furthermore, since the blocking between the surface protective films is reduced when the surface protective film is unwound at the time of bonding to the adherend, it is easy to unwind.
[0020]
The type of rubber on the surface of the pressing roll is not particularly limited, and silicone rubber or neoprene rubber is preferably used.
[0021]
In the surface protective film of the present invention, it is possible to add an antioxidant or a heat stabilizer as necessary, but it is desirable that the amount is as small as possible from the viewpoint of residual deposits on the adherend, preferably 500 ppm or less, preferably Is preferably suppressed to 250 ppm or less. Additives such as ultraviolet absorbers, antistatic agents, and metal deactivators may also be used, but it is desirable not to use them from the viewpoint of residual deposits on the adherend. It is desirable not to use a lubricant or an anti-blocking agent. These additives may be in the form of a masterbatch previously kneaded into a polyethylene resin such as low-density polyethylene, and there are no particular restrictions on the type of base polyethylene resin in the masterbatch unless the effects of the present invention are impaired. Absent.
[0022]
What is necessary is just to make a multilayer by coextrusion when making the polyethylene surface protection film of this invention a multilayer of two or more layers.
[0023]
The polyethylene surface protective film of the present invention is not only a resin plate and a metal plate, but also a liquid crystal substrate glass, a polarizing film for liquid crystal display, a thin display device film, a retardation film, a light diffusion sheet, an optical disk constituting film such as a DVD, It is suitably used as a surface protective film such as a precision fine coat face plate for optical applications.
[0024]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these Examples.
[0025]
The swell ratio was measured by the following method. The strand extruded by the same method as the method for measuring the melt flow rate under the conditions of a measurement temperature of 190 ° C. and a load of 2.16 kg according to JIS K7210 is cut, and the diameter of the portion 5 mm above the lowermost end of the strand is 90 The average value was calculated by measuring with a micrometer in two different directions. The average value was similarly obtained for each of the three strands, the three average values were further averaged, and the value obtained by dividing the average value by the inner diameter of the orifice was taken as the swell ratio.
[0026]
Example 1
Sumikasen CE3506 (swell ratio 1.33), a low-density polyethylene manufactured by Sumitomo Mitsui Polyolefin Co., Ltd. is used as the polyethylene resin, and melt extruded from the T die using a 90 mmφ single-layer extruder at a processing temperature of 290 ° C. A polyethylene surface protective film having a thickness of 40 μm was obtained by sandwiching between a mirror surface cooling roll having an average roughness (Rz) of 0.1 μm and a pressing roll having a surface made of silicone rubber and winding it with a winder.
The obtained polyethylene surface protective film was bonded to a polycarbonate plate with a rubber roller (load: 1.3 kg / 25 mm width). The cooling roll side, which is the side to be bonded to the adherend, could be bonded to the polycarbonate plate, but the pressing roll side for the purpose of preventing blocking showed no tackiness and could not be bonded. It was. Further, the cooling roll side was bonded to a polycarbonate plate and held at 60 ° C. for 97 days, and then the polyethylene surface film was peeled off. The surface of the polycarbonate plate was observed, but no deposits or fogging were observed. Furthermore, even if four sheets of the surface protection film with the cooling roll side bonded to the polyester film are stacked and pressed with a rubber roller weighing 2.65 kg and having a width of 10 cm, blocking is not possible between the pressing roll side and the polyester film side. It was not seen at all.
[0027]
Comparative Example 1
A polyethylene surface protective film was obtained in the same manner as in Example 1 except that a semi-matt cooling roll having a 10-point average roughness of 1.5 μm was used. The obtained polyethylene surface protective film was not sticky on both the cooling surface side and the pressing roll side, and could not be bonded to the polycarbonate plate.
[0028]
Comparative Example 2
A polyethylene surface protective film was obtained in the same manner as in Example 1 except that the pressing roll was not used. The obtained polyethylene surface protective film was able to be bonded to the polycarbonate plate on the cooling surface side and to the polycarbonate plate although the opposite surface side was somewhat weak. When four sheets of the surface protective film with the cooling roll side surface bonded to the polyester film were stacked and pressed with a rubber roller having a weight of 2.65 kg and a width of 10 cm, blocking was observed.
[0029]
【The invention's effect】
As described above, in the surface protective film that satisfies the conditions of the present invention, one side can be bonded to the adherend, and the opposite side cannot be attached at all. Even if they are stacked, blocking does not occur, and deposits do not remain on the adherend.

Claims (3)

In a method for producing a polyethylene surface protective film for winding a polyethylene melt film composed of a single layer or two or more layers melt-extruded from a T die, the surface of the cooling roll is roughened after the polyethylene melt film is extruded from the T die. Is sandwiched between a mirror surface cooling roll having a 10-point average roughness Rz of 0.5 μm or less and a pressing roll whose surface is made of rubber, and a method for producing a polyethylene surface protective film. The polyethylene constituting the layer in contact with the cooling roll of the polyethylene melt film is a low density polyethylene having a swell ratio of 1.45 or less, and the melt film is extruded from a T die at a temperature of 270 ° C. or more. The method according to claim 1. A polyethylene surface protective film obtained by the method according to claim 1.