JP4745927B2 - Base film for surface protection film - Google Patents

Description

The present invention relates to a method for producing a surface protective film that is temporarily attached to a surface of an optical application material that needs to be inspected for defects, and is used to protect the surface so that dust is not attached or scratched.

  Surfaces of stainless steel plates, aluminum plates, other metal plates, resin-coated plates, resin plates, decorative plates, and recently products such as liquid crystal displays such as personal computers, word processors, calculators, etc., such as polarizing plates, light guide plates, front plates A surface protective film is stuck on the surface of the material to prevent the surface from being damaged or contaminated with dirt, dust or the like during manufacture, transportation, storage or the like. And this surface protection film peels after use and is discarded.

  In addition to the function of surface protection, the surface protection film is required to have dimensional stability, rewinding property that does not cause blocking when the surface protection film wound in a roll shape is used after being rewound. For example, Patent Document 1 discloses a surface protective film excellent in unwinding properties comprising a base material layer having a low-density polyethylene as a main component and a surface roughness (Ra) of 0.08 to 2.00 μm and an adhesive layer. However, in Patent Document 2, a polyethylene molten film melt-extruded from a T-die is pressed against a mirror surface cooling roll having a 10-point average roughness (Rz) of 0.5 μm or less and a rubber surface. It has been proposed that a surface protective film can be obtained by sandwiching between rolls so that one side is smooth and the other side is polished and made glassy to prevent blocking during stacking.

  On the other hand, also in the base film used for the surface protection film, the purpose of preventing the so-called entanglement and blocking between the films due to the air that enters between the films when the formed film is wound up in a roll shape The surface of the film is roughened.

  However, the film whose surface is roughened has poor transparency, and there is a problem that defects in the product and the presence of foreign matter cannot be detected while the surface protective film described in Patent Documents 1 and 2 is stuck. There has been a demand for providing a surface protective film having excellent properties.

JP-A-5-229082 JP-A-2005-28618

The present invention does not occur blocking the generation or between films of aneurysm winding during winding, using a base fill-time for the surface protective film, yet provides an excellent method for producing a surface protection fill beam optical transparency For the purpose.

That is, according to the present invention,
(1) In the method for producing a surface protective film, the base film for a surface protective film is wound up in a roll shape and stored once, and then the base film wound in the roll shape is fed out and coated with an adhesive. hand surface of the surface roughness by JIS-B0601 (Ra) is less than 0.2, the surface of the other adhesive is applied (opposite surface) surface roughness by JIS-B0601 (Ra) is 0. method of manufacturing optical surface protective film, which comprises using a 2~2.0μm der Ru surface protective film substrate film.
(2) a surface protective film for the substrate film is characterized in that it is a polyethylene resin film (1) a surface protective fill beam method according.
(3) a surface protective film for the substrate film is characterized in that it is a three-layer film consisting of polyethylene-based resin (2) Surface protective fill beam method according.
(4) polyethylene resin is characterized in that it is a linear low density polyethylene or low density polyethylene resin (2) or (3) a surface protective fill beam method for producing according, is provided.

Surface protective fill beam for the substrate film of the present invention is one surface smooth surface, the other surface for discharging air that has entered between the film when wound into a roll smoothly because it is roughened It is possible to prevent the formation of an aneurysm (the occurrence of an aneurysm causes that part of the film to be stretched and the part to sag and cause uneven thickness), and at the same time, the films block together. Is also prevented. Moreover, in the present invention, since the adhesive (pressure-sensitive adhesive) is applied to the roughened surface, the rough surface portion is covered with the adhesive (pressure-sensitive adhesive), thereby preventing light scattering due to the roughening. has the advantage that Ru can be a transparent optical table surface protective film.

Hereinafter, the base film for a surface protective film of the present invention will be specifically described.
First, the base film for a surface protective film of the present invention is different from a normal transparent film having smooth both surfaces and a so-called double-sided embossed film having both surfaces roughened, and one surface is a smooth surface, and vice versa. The surface roughness (Ra) according to JIS-B0601 of the surface is 0.2 to 2.0 μm, preferably 0.2 to 1.0 μm.
If the surface roughness (Ra) according to JIS-B0601 of the opposite surface is less than 0.2 μm, air cannot be smoothly discharged when wound up in a roll shape, so that the prevention of curling which is the object of the present invention is prevented. This is not preferable because it cannot be expected to prevent blocking at the time of rewinding. Ra exceeding 2.0 μm is effective in preventing winding and blocking, but it is difficult to uniformly apply an adhesive. Therefore, it is not preferable.
In addition, in this invention, a smooth surface is a state equivalent to the surface state of a normal transparent film, for example, when shown by the surface roughness (Ra) by JIS-B0601, Ra is less than 0.2 micrometer and is normal. Means that Ra is about 0.1 μm or less.

  As a method for producing a base film for a surface protective film having the above-described characteristics, for example, (a) a method described in Patent Document 2 in which a thermoplastic resin is sandwiched between a mirror cooling roll and a pressing roll whose surface is rubber after extrusion molding In addition, when two types of raw material resins having different densities are used, the crystallization speed at the time of cooling and solidification after melt extrusion differs depending on the density difference, so that irregularities are naturally formed at the time of cooling and solidification. Applying a roughening technique (the method described in Patent Document 1) or a technique in which when a thermoplastic resin having a wide molecular weight distribution is used, a difference in resistance occurs in the die lip and the surface is roughened. A normal thermoplastic resin is used for the layer corresponding to this surface, and (b) two raw material resins having different densities and (c) a thermoplastic resin having a wide molecular weight distribution are used for the layer corresponding to the opposite surface. It can also be produced by a method of co-extrusion with use.

Examples of the thermoplastic resin used for the base film of the present invention include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, and ethylene-methyl methacrylate copolymer. Use polypropylene resin such as polyethylene resin, polyprene homopolymer, copolymer of propylene and other α-olefin, or nylon, polyester, polystyrene, etc. alone or in admixture of two or more. However, a polyethylene resin is preferable from the viewpoint of flexibility, followability, and the like, and in particular, transparency (in this case, a resin with less light scattering inside the film, meaning a resin with a small internal haze) is meant. Low-density polyethylene, linear low-density polyethylene, and resistance to low-density polyethylene. Preferably predominantly use linear low density polyethylene has excellent sex.
In addition, when the formation of the rough surface is achieved by selecting the raw material resin described in (b) and (c) regardless of the mechanical method of (a), the thermoplastic resin is appropriately mixed, Alternatively, a grade that easily forms a rough surface may be selected and used. Furthermore, in the present invention, a lubricant, an antiblocking agent, a heat stabilizer, an antioxidant, and other additives can be blended as necessary. However, these additives are preferably in a range that does not impair the transparency of the base film itself.

As described above, the film structure of the base film for a surface protective film of the present invention can be a single layer or a multilayer structure of two layers or three layers. However, it is easy to manufacture and impart various functions. In consideration of this, a multilayer structure is preferable, and a three-layer structure is particularly preferable for preventing the occurrence of curling. Preferred configurations include linear density polyethylene [LLDPE (rough surface)] / LLDPE / LLDPE (smooth surface) and LLDPE / LLDPE / low density polyethylene [LDPE (smooth surface)].
Moreover, the thickness of the base film for a surface protective film of the present invention is 20 to 100 μm, preferably 30 to 60 μm. In the present invention, it is desirable that the thickness is as thin as possible from the viewpoint of resource saving and cost reduction. In that case, it is preferable to use LLDPE.

  And the base film for surface protection films of this invention is wound up and stored in roll shape, and can be made into a surface protection film by apply | coating an adhesive to the rough surface side after that.

The thermoplastic resin used in the present invention is LLDPE-1.
Grade linear low density polyethylene (density 927kg / m3, MI = 2.0g / 10min, manufacturer: Prime Polymer Co., Ltd., trade name: EVOLUE SP2720) that provides a matte surface
・ LLDPE-2
It is a linear low density polyethylene (density 927 kg / m3, MI = 2.0 g / 10 min).
Moreover, the property of the obtained base film for surface protection films was evaluated with the following method.
<Haze>
The measurement was made according to JIS K7136.
<Surface roughness>
It measured based on JIS B0601.
<Occurrence of an aneurysm>
Actually, 4000 m of the product was wound up in a roll shape, and the presence or absence of the occurrence of an aneurysm was visually evaluated.
○: Not generated, ×: Generated <Transparency>
If the obtained base film for a surface protective film has a rough surface side, both surfaces are rough surfaces, and if both surfaces are smooth surfaces, an adhesive is applied to any smooth surface to apply the surface protective film. If the surface of the surface protection film is adhered to the surface of the test piece (acrylic plate) and the surface of the test piece appears clear from the surface protection film side, the result is ×. It was.

Example 1
Three layers consisting of LLDPE-1 / LLDPE-2 / LLDPE-2 using a multi-layer inflation molding machine consisting of three extruders by supplying LLDPE-1 to the outer layer, core layer and LLDPE-2 to the other outer layer In the present invention, the thickness ratio is 10/20/10 (μm), the total thickness is 40 μm, the surface on which LLDPE-2 is arranged is a smooth surface, and the surface on which LLDPE-1 is arranged is a rough surface. Such a base film for a surface protective film was obtained. Table 1 shows the haze, the surface roughness, the occurrence of an aneurysm, and the transparency of the obtained film when applied as a surface protective film by applying an adhesive.

Comparative Example 1
A base film for a surface protective film having a total thickness of 40 [mu] m was obtained with a single layer made of LLDPE-1 having both rough surfaces. Table 1 also shows the haze, surface roughness, generation of wrappings, and transparency when applied as a surface protective film by applying an adhesive.

Comparative Example 2
A base film for a surface protective film having a single layer of LLDPE-2 and having a smooth surface on both sides and an overall thickness of 40 μm was obtained. Table 1 also shows the haze, surface roughness, generation of wrappings, and transparency when applied as a surface protective film by applying an adhesive.

  As is clear from Table 1, the substrate film for a surface protective film according to the present invention can be rewound without generating a winding knob at the time of winding, and can be rewound without blocking at the time of rewinding. In addition, when used as a surface protective film, the surface state of the test piece appears to be clear, so that it was also suitable as a surface protective film for materials that require defect inspection such as optical applications. On the other hand, the base film for a surface protective film of Comparative Example 1 having both rough surfaces was easy to wind and unwind, but when used as a surface protective film, the surface state of the test piece can be seen. Therefore, it could not be used as a surface protective film for materials that require defect inspection such as optical applications. Furthermore, the base film for a surface protective film of Comparative Example 2 whose both surfaces were smooth surfaces could not be used as a surface protective film made of an elaborate material because of the occurrence of winding wounds during winding.

This onset Ming, PCs, word processing, product and its member such as a liquid crystal display of the calculator or the like, for example a polarizing plate, light guide plate, adhered to the surface of such the front plate, manufacturing, transport, of the surface during such storage it can damage or dust or the like is used for the production of surface protection fill beam to prevent from being contaminated by deposition. Particularly suitable product defects or remain stuck to the surface protective film, the production of necessary Ru optical surface protective film to detect the presence of foreign material.

Claims (4)

A surface protective film for the substrate film and stored temporarily wound into a roll, then the method for producing a surface protection film for applying an adhesive agent feeding the wound the base film has this roll, the hand The surface has a surface roughness (Ra) according to JIS-B0601 of less than 0.2, and the surface to which the other adhesive is applied has a surface roughness (Ra) according to JIS-B0601 of 0.2 to 2.0 μm. A method for producing an optical surface protective film, comprising using a base film for a surface protective film. Claim 1 surface protective fill beam method of manufacturing, wherein the surface protective film base film is a polyethylene resin film. Claim 2 surface protective fill beam method of manufacturing, wherein the surface protective film substrate film is a three layer film comprising a polyethylene resin. Claim 2 or 3 surface protective fill beam method according to, characterized in that the polyethylene resin is a linear low density polyethylene or low density polyethylene resin.