JPH10309781A - Surface protective film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface protective film having high transmission properties, small contamination of material to be covered and high anti-static effect. SOLUTION: This surface protective film comprises a base material layer molded by incorporating 1 to 100 pts.wt. of polyetheresteramide in 100 pts.wt. of synthetic resin such as polyethylene or polypropylene. An Adhesive used for the film is not particularly limited if the adhesive has characteristics of rereleasably adhering to a surface of a liquid crystal panel without paste residue or contamination. For example, the adhesive layer made of acrylic adhesive or ethylene-acrylic acid ester adhesive is laminated on the material layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a surface protective film. More specifically, the present invention relates to a removable surface protective film having an antistatic function used for protecting a liquid crystal panel, a polarizing plate, and a plastic resin plate during processing, transportation, or storage thereof.

[0002]

2. Description of the Related Art Removable surface protection made of synthetic resin in order to prevent scratches, adhesion of dust and contamination when processing liquid crystal panels and polarizing plates of personal computers, word processors, electronic desk calculators and the like. It has been practiced to attach a film to a liquid crystal panel or a polarizing plate for protection.

However, since the conventional surface protective film is made of a synthetic resin which is an insulator, static electricity is generated when the protective film is peeled off from a liquid crystal panel or the like after finishing the protective function, and as a result, the electronic circuit However, there are problems such as damage to the IC and adhesion of dust and dirt, and it was necessary to impart an antistatic function to the surface protective film.

As one of the methods, there is a method of kneading an antistatic agent such as a conductive filler or a surfactant into a base layer or a pressure-sensitive adhesive layer constituting a surface protective film.
The one into which the conductive filler was kneaded had poor transparency, and it was difficult to visually confirm the adherend surface with the surface protective film attached. Further, in order to obtain a target antistatic effect, a large amount of conductive filler must be added, which has led to a significant increase in manufacturing cost.

On the other hand, in the case where an antistatic agent such as a surfactant is kneaded, the antistatic agent bleeds out to the surface of the surface protective film and escapes static electricity therefrom to produce an antistatic effect. In general, many agents have a low molecular weight, the bleed-out amount is not stable, and the antistatic effect and the adhesive property are changed. Therefore, it has been difficult to obtain a surface protective film of a constant quality. In particular, when the amount of bleed-out becomes excessive, there is a fatal problem that the adherend is contaminated with a surfactant.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and an object of the present invention is to provide a surface protective film having a high permeability and a small antistatic effect with little contamination of an adherend. To provide.

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, by adding a polyetheresteramide to a base layer made of a synthetic resin, the mechanical strength of the base layer was not reduced, and The present inventors have found that the polyetheresteramide contained does not fall off the surface and contaminate the adherend, and that a stable surface protective film having excellent antistatic properties can be obtained, and the present invention has been completed.

[0008]

The surface protective film according to the present invention is a removable surface protective film in which a pressure-sensitive adhesive layer is laminated on a base layer made of a synthetic resin. It is characterized by containing.

In the present invention, the term "polyetheresteramide" broadly refers to a copolymerized product of a polyamide block having a reactive terminal and a polyether having a reactive terminal. The term means not only a polymer formed by a random chain of monomer components, but also a block polyetheresteramide, that is, a polymer in which various components are formed by blocks having a predetermined chain length.

As the polyetheresteramide used in the present invention, for example, JP-A-1-163234, JP-B-4-5691, JP-A-7-18847.
No. 6 can be used.

Among these, the number average molecular weight is 200 to
5,000 polyamide and number average molecular weight 300 ~
A polyether esteramide derived from an alkylene oxide adduct of 5,000 bisphenols and / or a polyoxyalkylene glycol is preferable, and particularly a number average molecular weight having a carboxyl group at both terminals of 200 to 200.
5,000 polyamide and number average molecular weight 300 to 50,000
A polyetheresteramide derived from an alkylene oxide adduct of a bisphenol of 00 is preferred.

When the polyamide has a number average molecular weight of less than 200, the heat resistance of the polyetheresteramide is deteriorated, which is not preferable for producing a base material layer. On the other hand, when the number average molecular weight exceeds 5,000, it is difficult to obtain polyetheresteramide itself, and a surface protective film cannot be obtained at low cost. When the number average molecular weight of the alkylene oxide adduct of bisphenols or polyoxyalkylene glycol is less than 300, the antistatic effect is insufficient. On the other hand, when the number average molecular weight is 5,0
If it exceeds 00, it is difficult to obtain polyetheresteramide itself, and a surface protective film cannot be obtained at low cost.

The synthetic resin used for the base layer is not particularly limited as long as it is used as a surface protective film. For example, polyethylene, polypropylene, polyester, polyvinyl chloride, polyamide, ethylene / propylene copolymer Examples include various synthetic resins such as coalescing and polystyrene, and one or more of these are used. Moreover, you may use these laminated bodies as needed.

At this time, the polyetheresteramide is preferably mixed in an amount of 1 to 100 parts by weight, more preferably 5 to 50 parts by weight, based on 100 parts by weight of the synthetic resin. If the amount is less than 1 part by weight, almost no antistatic effect can be obtained, and even if it is more than 100 parts by weight, the mechanical strength of the obtained base material layer is not sufficient,
It is economically disadvantageous because the antistatic effect is not improved.

The base material layer is prepared by adding the above-mentioned polyetheresteramide to these synthetic resins. The base material layer further has an antistatic property in addition to the synthetic resin and the polyetheresteramide. For the purpose of improvement, a halogen compound of an alkali metal and / or an alkaline earth metal may be contained as necessary. Also, various known nonionic, anionic, cationic or amphoteric surfactants can be mixed. Furthermore, as long as it does not deteriorate the function as a surface protective film such as transparency and antistatic properties, it can be added to other ordinary base material layers depending on the purpose of use, for example, pigments, dyes, plasticizers , An antioxidant, an ultraviolet absorber, a slip agent, and the like.

In order to form the base material layer, the synthetic resin and the polyetheresteramide are mixed so as to have a mixing ratio within the above range. At this time, the synthetic resin and the polyetheresteramide are kneaded at once and the base is kneaded. There is a method for preparing a material layer, and a method called so-called master batch or master pellet in which a part of the synthetic resin is kneaded in advance with the polyetheresteramide and then the remaining synthetic resin is kneaded. Generally, it is preferable to use a master batch or a master pellet from the viewpoint of uniformly mixing the polyetheresteramide. The master batch or the master pellet is supplied, for example, from Sanyo Chemical Industries, Ltd. under the trade name “Perestat Series”. That is, the masterbatch (master pellet) and the synthetic resin forming the base material layer are mixed so as to have the mixing ratio described above, and a sheet-like base material layer can be obtained by an ordinary method. Further, as described above, a resin different from the remaining synthetic resin mixed with the synthetic resin used for the master batch or the master pellet may be used.

The pressure-sensitive adhesive used for the surface protective film of the present invention is not limited as long as it has a property that it can be removably adhered to a panel surface of a liquid crystal panel without glue or contamination.
There is no particular limitation. For example, various pressure-sensitive adhesives such as acrylic, natural rubber, synthetic rubber, ethylene-vinyl acetate copolymer, ethylene-acrylate ester, styrene-isoprene block copolymer, styrene-butadiene block copolymer, and the like. And one or more of these can be used.

The method for laminating the pressure-sensitive adhesive layer on the base material layer is not particularly limited, and any method may be employed.
One surface of the base material layer can be subjected to a corona discharge treatment to apply the above-mentioned pressure-sensitive adhesive solution. If necessary, various kinds of antistatic agents, slip agents, antioxidants and other additives used in general adhesives for surface protective films can be added to the adhesive solution.

In the surface protective film of the present invention, the thickness of the substrate layer and the thickness of the pressure-sensitive adhesive layer are appropriately determined depending on the application, but the thickness of the substrate layer is generally from 10 to 100.
μm, preferably 30 to 70 μm. The thickness of the pressure-sensitive adhesive layer is generally 1 to 50 μm, preferably 3 to 15 μm.
m.

[0020]

EXAMPLES Next, various examples of the surface protective films of the examples of the present invention and the surface protective films of the comparative examples were produced, and the effects of the present invention were confirmed. In the following, “%” and “parts” mean “% by weight” and “parts by weight”, respectively. Further, the present invention is not limited to each of these embodiments.

(Example 1) MFR (Melt flow rate, according to JIS K7210 "Method for testing the flow of thermoplastics"; the same applies hereinafter) 3.0, density 0.92
g / cm ³ of low-density polyethylene and master pellets containing polyetheresteramide (containing polyetheresteramide, manufactured by Sanyo Chemical Industries, Ltd.)
After 30% of a kneading antistatic agent for polyethylene-based resin (Perestat 2150) was dry-blended, the mixture was extruded at a resin temperature of 190 ° C. using a T-die extruder (40 mmφ) to form a film having a thickness of 60 μm. The moldability was good, and the appearance of the obtained film was also good.

One surface of the film obtained above was subjected to a corona discharge treatment, and the treated surface was treated with 100 parts of a copolymer of butyl acrylate / acrylic acid = 95/5 (weight ratio) to tetraglycidyl-1,3. An acrylic pressure-sensitive adhesive to which 3 parts of bisaminomethylcyclohexane was added was applied so that the coating film had a solid content of 5 μm, and was then dried in a dryer at 80 ° C. for 2 minutes to obtain a surface of Example 1. A protective film was obtained.

(Example 2) MFR 3.0, density 0.92
A mixture in which 70% of low-density polyethylene (g / cm ³ ) and 30% of the master pellet containing the polyetheresteramide used in Example 1 were dry-blended was used as a base layer constituent resin. 95g / c
vinyl 11% acetate content ethylene m ³ - using vinyl acetate copolymer as an adhesive layer constituting the resin, a two-layer co-extrusion method to obtain a surface protective film of Example 2. The thickness of this product was 60 μm, the thickness of the base material layer was 45 μm, and the thickness of the pressure-sensitive adhesive layer was 15 μm.

Example 3 MFR 9.0, density 0.90
g / cm ³ of polypropylene 80% and master pellets containing polyetheresteramide (containing polyetheresteramide, Sanyo Kasei Kogyo Co., Ltd., kneading antistatic agent Pelestat 3 for polypropylene resin)
170) After dry blending of 20%, the mixture was extruded at a resin temperature of 230 ° C. by a T-die extruder (40 mmφ) to form a film having a thickness of 40 μm. The moldability was good, and the appearance of the obtained film was also good. Thereafter, a pressure-sensitive adhesive layer was laminated in the same manner as in Example 1 to obtain a surface protective film of Example 3.

(Example 4) MFR 9.0, density 0.90
g / cm ³ of polypropylene 70%, MFR 3.0, density 0.92 g / cm ³ of low-density polyethylene 10%, and 20% of master pellets containing the polyetheresteramide used in Example 3 were dry-blended. T
Resin temperature 230 with a 40mm diameter die extrusion molding machine
C. and extruded into a film having a thickness of 40 μm. The moldability was good, and the appearance of the obtained film was also good. Thereafter, a pressure-sensitive adhesive layer was laminated in the same manner as in Example 1 to obtain a surface protective film of Example 4.

(Comparative Example 1) MFR 3.0, density 0.92
g / cm ³ of low-density polyethylene (90%) and 10% of a nonionic surfactant-type antistatic agent (Sanyo Chemical Industry Co., Ltd. Chemistat 1100) were dry-blended, and then resin was formed using a T-die extruder (40 mmφ). It was extruded at a temperature of 190 ° C. and formed into a film having a thickness of 60 μm. The moldability was good, but some stickiness was observed on the film surface. Thereafter, a pressure-sensitive adhesive layer was laminated in the same manner as in Example 1 to obtain a surface protective film of Comparative Example 1.

Comparative Example 2 MFR 3.0, density 0.92
g / cm ³ of low density polyethylene was extruded at a resin temperature of 190 ° C. using a T-die extruder (40 mmφ).
It was formed into a film having a thickness of 60 μm. Thereafter, the first embodiment
In the same manner as described above, the pressure-sensitive adhesive layer was laminated to obtain a surface protective film of Comparative Example 2.

Comparative Example 3 MFR 9.0, density 0.92
g / cm ³ of low-density polyethylene was extruded at a resin temperature of 230 ° C. by a T-die extruder (40 mmφ),
It was formed into a film having a thickness of 40 μm. Thereafter, the first embodiment
The pressure-sensitive adhesive layer was laminated in the same manner as described above to obtain a surface protective film of Comparative Example 3.

[Characteristic Test] The following tests were performed on the surface protective films of Examples 1 to 4 and Comparative Examples 1 to 3 obtained above. As a characteristic test, adhesive strength, appearance, contamination to an adherend, electrical properties (surface resistivity, peeling voltage), and mechanical properties (elastic modulus, breaking strength) were measured.

(Adhesive strength) Each surface protective film is 20 mm
The sheet was cut into a width and attached to an acrylic resin plate ("Acrylite L" manufactured by Mitsubishi Rayon Co., Ltd .; the same applies hereinafter) by reciprocating a 2 kgf roller once, and after 30 minutes, the tensile speed was 300 m.
m / min and a peel angle of 180 ° were measured by a tensile tester.

(Appearance) The surface protective film was evaluated for any significant difference from the films of Comparative Examples 2 and 3 in which the antistatic agent was not incorporated. Without loss of transparency, and when there is no surface stickiness due to bleed-out of the antistatic agent, it is ○, and when there is surface stickiness due to bleed-out of the film or the antistatic agent, it is as ×. evaluated.

(Contamination to the adherend) Each surface protective film was cut into a width of 20 mm, affixed to an acrylic resin plate by reciprocating a 2 kgf roller once, stored at 50 ° C. for 24 hours, and then peeled off by hand. The acrylic resin plate was visually evaluated for contamination. When there was no contamination on the acrylic resin plate, it was evaluated as ○, and when there was contamination, it was evaluated as ×.

(Electrical Characteristics) Surface resistivity According to the method specified in JIS K6911 “General Test Method for Thermosetting Plastics”, 25 ° C., 65% R.H. H.
Under the atmosphere described above, measurement was performed on each of the surface of the base material layer and the surface of the pressure-sensitive adhesive layer. Peeling charge voltage Each surface protective film is attached to the surface of a polarizing film for liquid crystal display attached to an acrylic resin plate having a size of 70 mm × 100 mm, and then the attached surface protective film is peeled off by hand. The charged potential charged on the polarizing film was measured at 25 ° C. and a humidity of 65% R.V. by a collecting potential meter (KS-471, manufactured by Kasuga Electric Co., Ltd.).
H. It measured under the atmosphere of.

(Mechanical Properties) The surface protective film was cut into a width of 20 mm, and the distance between the chucks was set to 50 mm and the tensile speed was set to 300 m using a tensile tester.
A tensile test was performed at m / min. The elastic modulus was determined from the slope of the initial tangent line of the stress-strain curve obtained by the tensile test. Rupture strength was determined from the strength at the time of film breakage in the above tensile test.

Table 1 summarizes the results of the above characteristic tests.

[0036]

[Table 1]

As can be seen from Table 1, the surface protective films of the examples all had good transparency and appearance, and did not contaminate the adherend. The adhesive strength was low with the surface protective sheet of Example 2, but there was no problem with the actual adhesiveness, and there was no effect of the polyetheresteramide contained in the base material layer. Further, with respect to the electrical characteristics, the surface resistivity was reduced as well as or more than the case where the surfactant was kneaded, and the peeling charge voltage was also effectively reduced. Also, the mechanical properties were not affected by the polyetheresteramide, and a surface protective film having sufficient mechanical strength could be obtained.

[0038]

According to the surface protective film of the present invention, in a removable surface protective film in which a pressure-sensitive adhesive layer is laminated on a substrate layer made of a synthetic resin, the substrate layer contains polyetheresteramide. Therefore, a surface protective film having high mechanical strength and transparency, and less contamination of the adherend and high antistatic effect can be obtained.

Therefore, no static electricity is generated during the work of attaching and detaching the protective surface film, and it is possible to prevent the IC incorporated in the circuit near the liquid crystal panel or the polarizing plate from being broken by the static electricity. Further, it is possible to prevent a reduction in commercial value without adhering dirt and dust, and to prevent contamination due to bleed out of the antistatic agent. Furthermore, since it has high transparency, it is easy to process even with the surface protective film attached, and the surface of the adherend can be easily visually confirmed. As described above, the present invention can provide an excellent surface protective film that is effective for processing, transportation, and storage.

Claims (2)

[Claims] 1. A releasable surface protective film comprising a pressure-sensitive adhesive layer laminated on a substrate layer made of a synthetic resin, wherein the substrate layer contains polyetheresteramide. 2. 100 parts by weight of the synthetic resin of the base material layer,
2. The surface protective film according to claim 1, comprising 1 to 100 parts by weight of polyetheresteramide.