Stock material or miscellaneous articles – Layer or component removable to expose adhesive
Reexamination Certificate
2001-06-01
2003-06-24
Ahmad, Nasser (Department: 1772)
Stock material or miscellaneous articles
Layer or component removable to expose adhesive
C428S001100, C428S040200, C428S040500, C428S041300, C428S041400, C428S041500, C428S041700, C428S041800, C428S480000, C428S906000, C428S918000
Reexamination Certificate
active
06582789
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a surface protective film and more specifically to a surface protective film that has an adhesive layer which can be easily peeled off after stuck on a substrate, which has a peel force that does not increase with time and which has no liftings caused by the air bubbles trapped when the film is stuck on a substrate having a rough surface, and further that is so highly transparent that the inspectability of the substrate stuck with it is not impaired.
BACKGROUND ART
A surface protection film is the composition of having used the plastic film as the base film generally, and having prepared the adhesion agent layer in one side of the base film. In recent years, its use for protecting the surface of an optical component has been becoming increasingly popular. For example, in a process for producing a variety of display such as a television, computer, word processor, car navigation system, it is used for protecting the surface of them. Above all, it is used for protecting not only the surface of liquid crystal display (LCD) which has spread rapidly now but also the surfaces of optical components and optical laminates such as a polarizer, optical retardation film and viewing angle-widening film in a process for producing LCD. In general, a transparent film, for example, olefin-based film such as a polyethylene or polypropylene is used as the base film of the surface protective film, and the surface protective film is peeled off and discarded when the production of LCD is complete or when it is actually used.
In recent years, TFT-LCD in particular has been receiving attention due to its high resolution and high-speed response, and the requirements for the surface protective film covering the display during its production process have been made more rigorous. For example, in the process for producing a polarizer or LCD, the product is often inspected for the presence of defects with the surface protective film stuck thereon. It has been difficult to inspect the product itself with high precision, because in the case of the usual olefin-based film such as the polyethylene film, it is no good transparency and has many gels such as fisheyes that maybe particles. And a surface protective film will be stuck in many cases to the following manufacturing process for a long time, once it is stuck on the polarizer or LCD. After inspection had been completed, there was a problem that workability became bad when the surface protective film was peeled off and the peel force was increased after inspection had been completed, or defects, such as generating of the particles and distortion, arose in inspection of the display when a part of adhesive layer remained.
Some of display components such as a polarizer have minute unevenness in the surface to control reflection of light to protect glare on display. Meanwhile, it is generally practiced to be a rigid adhesive layer to have re-release characteristics by reducing the adhesion, for example, by increasing the cohesion of the adhesive or by mixing a large amount of components having a high glass transition temperature (Tg) or hard segments. When the surface protective film which has such an adhesive layer is stuck on the surface in which is prepared unevenness, the portions that cannot contact the adhesive layer with the surface may occur mainly because the adhesive is not fully smeared and does not spread on the surface. As a result, since it becomes air bubbles and remains without air falling out in these portions, it may become a problem at the time of inspection.
In addition, a release film is generally applied to the surface of the adhesive layer of an unused surface protective film at the step of forming the adhesive layer, and the surface protective film is rolled up with the release film to be a final product. However, since the release film is just peeled off and discarded when the surface protective film is used, it is necessary to eliminate the release film in consideration of production of waste and costs.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a surface protective film that has an adhesive layer which can be easily peeled off after stuck on a substrate, which has a peel force that does not increase with time and which has no liftings caused by the bubbles trapped when the film is stuck on a substrate having a rough surface and that is so highly transparent that the inspectability of the substrate stuck with it is not impaired.
It is another object of the present invention to provide a surface protective film having an adhesive layer which leaves no adhesive residues and a smooth adhesive surface.
It is another object of the present invention to provide a roll of a surface protective film which can be rolled up without sticking a release film on the adhesive layer of a surface protective film, if necessary can be easily peeled off a substrate on which is stuck the unrolled surface protective film, has a peel force that does not increase with time, and is so highly transparent that the inspectability of the substrate stuck with it is not impaired.
Other objects and advantages of the present invention will be apparent from the following description.
According to the present invention, firstly, the above objects and advantages of the present invention can be achieved by a surface protective film for protecting the surface of a substrate, which comprises a polyester film (A) and an adhesive layer (B) formed on one surface of the polyester film (A) and has a critical bounce coefficient of not more than 0.5.
The above surface protective film preferably has the following properties and constitution. The adhesive layer (B) satisfies all of the following properties (1) to (4).
(1) The dry adhesion against a stainless steel plate is 30 to 500 mN/25 mm (3 to 50 g/25 mm).
(2) The rate of change in the dry adhesion after kept in a stuck position for a week at 60° C. is 0.5 times to 2.0 times.
(3) The size of a ball used in ball tack measurement is {fraction (2/32)} inches to {fraction (10/32)} inches.
(4) The thickness of the adhesive layer (B) is 5 &mgr;m to 50 &mgr;m.
According to the present invention, secondly, the above objects and advantages of the present invention can be achieved by a film roll in the form of the roll with which the surface protective film of the present invention is rolled round in the state where the adhesive layer (B) and a protective layer (C) are contacted directly.
The present invention will be described in detail hereinafter.
The surface protective film of the present invention comprises at least a polyester film (A) and an adhesive layer (B). Further, a protective layer (C) containing at least either an antistatic agent or a release agent can be formed on the surface reverse to the surface on which the adhesive layer is formed. Further, a release layer (E) can be formed on the adhesive layer (B).
Polyester Film
The base film (layer A) of the surface protective film used according to the present invention is a polyester film, which is excellent in transparency, productivity and workability. The polyester film is not limited to a particular kind but is preferably a polyethylene terephthalate film or a polyethylene-2,6-naphthalenedicarboxylate film. Further, it may take a multi-layer structure obtained by co-extrusion and comprising any number of layers. The polyester constituting the polyester film is preferably a crystalline, linear saturated polyester such as a polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphtahlenedicarboxylate, copolymers obtained by substituting portions of these compounds with other components, and mixtures of these compounds with polyalkylene glycol or other resins.
The polyester film used in the present invention may be an unstretched polyester film, a monoaxially oriented polyester film or a biaxially oriented film. The biaxially oriented polyester film is preferable from the viewpoints of productivity and handling properties.
The biaxially oriented
Ahmad Nasser
Teijin Limited
LandOfFree
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