Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Reexamination Certificate
1999-03-15
2002-05-07
Thibodeau, Paul (Department: 1773)
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
C428S336000, C428S421000, C428S522000
Reexamination Certificate
active
06383620
ABSTRACT:
This application is the national phase under 35 U.S.C. §371 of prior PCT International Application No. PCT/JP97/02811 which has an International filing date of Aug. 12, 1997 which designated the United States of America.
FIELD OF THE INVENTION
The present invention relates to an antiglare-treated article. In particular, the present invention relates to an antiglare-treated article having a fluorine-containing polymer coating on its surface.
PRIOR ART
In recent years, displaying instruments are often used outdoors, as small-sized information terminals such as liquid crystal TV or PDA (persona digital assistants), and video cassette recorders having a liquid crystal display become popularized. In such cases, external light is reflected mainly on the surface of a display, and thus visibility of the display sometimes severely deteriorates. When such instruments are used indoors, room lights or users themselves are mirrored on the display surface, so that the contrast of images deteriorates. Therefore, it is desirable to perform an antiglare treatment on display surfaces in order to improve the image quality.
In the case of apparatuses using sun light such as solar batteries, solar water heaters, etc., about 10% of solar light cannot reach the apparatuses since it is reflected on protection plates. If an antiglare treatment is preformed on protection plates, the energy loss caused by reflection decreases, and thus the energy-conversion efficiency of the apparatuses can be easily improved.
Some reflection may make showcases or show-windows more attractive as a whole. However, it may be necessary to decrease the reflection of external light on the glass surfaces for the original purpose to show goods clearly.
In the field of floor model displays, projection TV and plasma displays are become popularized, and it is expected that the size of a display screen will further increase. In such a case, the edge parts of the display screen suffer from the influence of the reflection of external light, since the angle of visibility is widened so that an angle between the line of vision and the display screen decreases at the edge parts of the screen. Thus, it is desirable to perform an antiglare treatment on display surfaces in order to display beautiful images in every corner of the displays.
Antiglare treatment is roughly classified into non-glare treatment and anti-reflection (AR) treatment.
The non-glare treatment is widely employed, since is very economical of material costs and processing costs, and achieves effects to some extent. However, the non-glare treatment cannot avoid the blur of images which are seen through a treated film, since it simply blurs the reflected images by light-scattering. Thus, the non-glare treatment is not suitable for displays which require high definitions such as high-definition TV or digital video equipment. Furthermore, the non-glare treatment scatters not only the reflected light but also transmitted light. Thus, it has adverse effects on the improvement of light transmission.
JP-A-2-245702 and JP-A-7-168006 disclose methods for the decrease of a reflectance by forming coatings having refractive indexes which decrease stepwise from the refractive index of a substrate. The disclosed methods can decrease the reflectance to about a quarter, but a part of such decrease may result from the non-glare effect. Thus, the same drawbacks as those caused by the above non-glare treatment may arise.
Accordingly, the AR treatment is preferable as the antiglare treatment. However, till lately, only vapor deposition multi-layer films are known as films which are practically useful from the viewpoint of abrasion resistance and antiglare properties. The formation of vapor deposition films has drawbacks in that they require large-scale equipment, have low productivity and need high treatment costs. Furthermore, the sizes of articles which can be treated are limited.
To overcome such drawbacks, a method is proposed, which comprises successively performing the antiglare treatment on a continuous substrate by the formation of a resin film having a low refractive index, which greatly improves the productivity.
In general, in the case of the AR treatment with a resin, the thickness of an anti-reflection film is preferably about 0.1 &mgr;m, and the anti-reflection effect increases as the refractive index of the resin decreases. Thus, fluororesins are often used as resins for anti-reflection treatment (see JP-A-6-136064, JP-A-7-126552, JP-A-2-19801, JP-A-7-168003, JP-A-7-168005 (=U.S. Pat. No. 5,449,558), etc.).
The abrasion resistance of a film is as important as a refractive index. A film does not have sufficient abrasion resistance, when a resin is simply applied. Thus, it has been tried to improve the abrasion resistance of a resin film.
One method for the formation of an anti-reflection film from a resin comprises the curing of a solution containing an acrylic monomer, which is disclosed in JP-A-6-136064 and JP-A-7-126552. However, fluorine-containing acrylic polymers usually have a refractive index of 1.36 or more. Some fluorine-containing acrylic polymers have a lower refractive index than 1.36. However, such a low refractive index may be considered as that of polymers containing a relatively large amount of unreacted monomers. The refractive index of a fluorine-containing acrylic polymer increases while antiglare effects deteriorate, when the amount of fluorine-free reactive groups is increased to improve the hardness of a film by crosslinking or to improve the adhesion properties of the formed film.
In addition, the above method has two problems. One problem is that the method includes a photo-curing process. Since the thickness of an anti-reflection film is usually about 0.1 &mgr;m, the surface area of the film is very large in comparison with the film thickness, and thus the resin is easily in contact with polymerization inhibitors such as oxygen in an air, so that a curing reaction does not steadily proceed. A large amount of a polymerization initiator should be added to stabilize the polymerization reaction. However, the polymerization initiators increase a refractive index and thus deteriorates the antiglare effect of the resin. Another problem is that the fluctuation of a reaction rate leads to the fluctuation of a time until the complete curing. As a result, the total amount of monomers which evaporate fluctuates, and thus the thickness of an anti-reflection film may not be stabilized. In addition, a resin film cannot be re-coated, since the method includes a curing step.
An anti-reflection film comprising a fluorine-containing alicyclic polymer is also known from, for example, JP-A-2-19801. The refractive index of this polymer is as low as 1.34. When an undercoat is made in the form of a self-restorable film as disclosed in JP-A-7-168005, no process is necessary to improve the abrasion resistance by curing. Thus, the productivity of anti-reflection films greatly increases.
However, alicyclic perfluoropolymers can be dissolved only in very expensive fluorine-containing solvents such as perfluoro(2-butyltetrahydrofuran), perfluorobenzene, etc. Thus, the treatment costs greatly increase. In addition, such fluorine-containing solvents have a drawback that their evaporation rates are too high. Therefore, a film-formation method is practically limited only to a coating method which is called a die coating method that is disclosed in JP-A-7-151904.
The refractive index of a fluorine-containing alicyclic polymers is 1.34 or larger, which is higher than that of perfluoropolyethers, perfluoroelastomers, etc. (e.g. about 1.30). Antiglare-treated articles which are treated with the fluorine-containing alicyclic polymers have inferior antiglare effects to those treated with TEFLON AF (trademark), perfluoropolyethers, perfluoroelastomers, etc.
TEFLON AF (trademark) and perfluoroelastomers have high antiglare effects, but their abrasion resistance has not been improved to a practically satisfactory level.
It was tried to form a film having abrasion resistance by curing per
Aoyama Takahisa
Nagahama Norio
Otsuki Norihito
Shimizu Tetsuo
Birch & Stewart Kolasch & Birch, LLP
Daikin Industries Ltd.
Thibodeau Paul
Zacharia Ramsey
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