Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Adhesive outermost layer
Reexamination Certificate
2001-12-06
2003-11-18
Seidleck, James J. (Department: 1711)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Adhesive outermost layer
C428S3550AC, C428S3550EN, C428S423700, C428S480000, C428S483000
Reexamination Certificate
active
06649260
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical coating film using a biaxial oriented thermoplastic resin film as a base film.
2. Description of the Background Art
Biaxial oriented thermoplastic resin films made from polyester or the like have been widely used as various optical films that are applied with light being transmitted or reflected, because of their superior transparency, dimension stability and chemical resistance. In particular, with respect to the applications such as base films for prism lens sheet and base films for hard coating film, used for liquid crystal displays (LCDs), base films for anti-reflection (AR) film, base films for diffusion plate, anti-destruction films for cathode ray tube (CRT), transparent conductive films used for touch panel and electro-luminescence, and near-infrared-ray absorbing films and electromagnetic wave absorbing films used for front panel of plasma display, comparatively thick films are used since superior strength and dimension stability are required.
Such optical films are required to have superior transparency and to exert a superior adhesive property to other films when they are subjected to a prism lens process, a hard coating process or an AR process, and the films are further desired to be less susceptible to optical defects therein.
Normally, in order to improve its handling properties (sliding property, winding property, anti-blocking property, etc.) and scratch resistant property of a film, processes for allowing the film to contain particles and for forming irregularities on the surface thereof have been generally carried out. However, in general, the transparency of the film tends to decrease due to the great difference in refractive indexes between the particles and polyester and voids generated on the periphery of each particle at the time of film orientation.
Therefore, when the content of particles in the base film is reduced for the purpose of obtaining a highly transparent film, the optical defects become more apparent while the transparency is improved.
In particular, generally, conventional biaxial oriented polyester films are inferior in adhesive property with respect to other materials, such as prism lens layers and hard coating layers mainly made from acrylic resins.
Moreover, scratches on the surface of the base film form one of reasons of optical defects in the film. In the case when there are fine scratches on the surface of a base film, if this is formed in, for example, a lens sheet, the scratches on the surface of the base film might be enlarged by a lens layer or cause optical defects on the display portion in a liquid crystal display.
With respect to a technique for suppressing the occurrence of these scratches, Japanese Unexamined Patent Publication No. 9-183201 (1997) discloses a polyester optical film in which a surface active agent is provided on the film surface so that scratches being 20 mm or more in length and 0.5 &mgr;m or more in the maximum depth are reduced to 10 pcs/m
2
or less. However, this technique fails to suppress the occurrence of more finer scratches, failing to satisfy the level of quality that has been required for the recent optical films.
The present invention has been devised to solve the above-mentioned problems, and its principle object is to provide an optical coating film that is less susceptible to optical defects. Furthermore, another object is to provide an optical coating film that is superior in transparency and adhesive property.
SUMMARY OF THE INVENTION
The inventors of the present invention have made extensive studies in order to achieve the above-mentioned objects, and have found that it is effective to reduce the optical defects to reduce the number of scratches having a specific form on the surface of a base film to not more than a specific value, thereby leading to the completion of the present invention.
In other words, the present invention provides an optical coating film which uses a transparent biaxial oriented thermoplastic resin film having a thickness of 50 &mgr;m or more as a base film, and has an adhesive property modifying resin layer on at least one surface of said base film, wherein the number of scratches being 1 &mgr;m or more in depth and 3 mm or more in length on the surface of said coating film is 100 pcs/m
2
or less.
In general optical applications, the number of scratches on the surface of the coating film is required to be reduced to 100 pcs/m
2
or less. For example, the level in which the number of scratches on the surface of the coating film is 100 pcs/m
2
or less corresponds to a level in which in the application such as a film for diffusion plate with light rays being observed in a diffused state, those scratches are not recognized as optical defects. Moreover, in the A-class optical application such as liquid crystal protection films, general hard coating films, anti-reflection films, near-infrared-rays absorbing films with transmitting light rays being directly observed, the number of scratches on the surface of the coating film is preferably reduced to 30 pcs/m
2
or less, which corresponds to a level in which no adverse effects are found even when directly viewed. Furthermore, in the special A-class optical application such as lens films with scratches on the film surface being projected in an enlarged manner and transparent conductive films for touch panel with a hard coating layer on the surface and a transparent conductive film on the rear surface, the number thereof is preferably reduced to 10 pcs/m
2
or less.
When the number of scratches having such a size exceeds the above-mentioned ranges, the optical defects increase, causing serious degradation in the quality of optical films. Here, “the surface of a coating film” includes both of the surfaces with the above-mentioned adhesive property modifying resin layer and without such a layer.
Moreover, with respect to the above-mentioned scratches, the numbers of scratches in the longitudinal direction and/or scratches in the lateral direction are preferably 50 pcs/m
2
or less, respectively. More preferably, the numbers of scratches in the respective directions are 30/m
2
or less, respectively and most preferably to 10/m
2
or less.
Here, the scratches in the longitudinal direction refer to scratches having a deviation of ±45° or less from the longitudinal direction of the optical coating film in the longest direction. That is, supposing that the traveling direction at the time of manufacturing the optical coating film is the longitudinal direction, those scratches have offsets not more than ±45° from the direction parallel to the winding direction at the time of manufacturing the film. The scratches in the lateral direction refer to scratches that have a deviation of ±45° or less from the width direction of the optical coating film in the longest direction, that is, from the direction perpendicular to the winding direction at the time of manufacturing the film.
In the present invention, “scratches” refer to fine recessed portions and/or protruding portions on the surface of an optical coating film, and includes portions in a protruding state. Here, when the surface of an optical coating film is observed in the vertical direction, irregularities of scratches closely located within 50 &mgr;m are defined as the same scratch, and the length and width of a rectangular having a minimum area covering the outermost portions of these scratches are set to the length and width of the scratch. However, even when considered to be the same upon observing with the naked eye, some scratches might be separated when observed under a microscope, the length and width of a scratch are defined as described above. Moreover, the depth of a scratch means the greatest depth in the thickness direction from the surface of an optical coating film, and when the film surface has a swelling portion due to the scratch, the depth of the scratch means the greatest depth from the top of the swelling portion to the bottom thereof.
In a pr
Ito Akira
Kumano Katsufumi
Oda Naonobu
Bissett Melanie
Foley & Lardner
Seidleck James J.
Toyo Boseki Kabushiki Kaisha
LandOfFree
Optical coating film does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical coating film, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical coating film will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3136577