Patent Application
20080042996
The above object and features of the present invention will be more apparent from the following description of the preferred embodiment with reference to the accompanying drawings, wherein:
In the prior art, the upper transparent substrate of the touch panel has been made up of polarizing plate 8, PET film 2, and transparent electrically conductive film 3, as previously shown in
By contrast, the present invention provides a distinctive feature that eliminates the need for the PET film 3 and that allows the upper transparent substrate of the touch panel to be made up of the polarizing plate 8 and the transparent electrically conductive film 3. Embodiments of the present invention will be described below.
In the present invention, the PET film 2 is omitted and, therefore, is not shown. The electrically conductive polymer layer 3 is formed to a thickness of 100 nm to 200 nm over the entire surface of the polarizing plate 8. The ITO 6 is deposited in the form of a film over the entire surface of the glass substrate 4.
In the present embodiment, glass coated with an ITO film having good transmissivity has been used as the lower transparent substrate but, alternatively, a glass substrate coated with an electrically conductive polymer as a transparent electrically conductive film or a transparent resin substrate coated with a transparent electrically conductive film such as ITO or an electrically conductive polymer may be used as the lower transparent substrate.
In the prior art, the upper transparent substrate has been constructed by disposing the polarizing plate 8 on one surface of the PET film and the ITO electrode on the lower surface thereof, as earlier described. On the other hand, the present inventors have devised a polarizing plate that eliminates the need for the PET film and that can, by itself, function as the upper transparent substrate, as described above. As a result, the manufacturing process for the PET can be omitted.
The upper transparent substrate is fabricated in accordance with a first fabrication process or a second fabrication process, as will be described below.
First, the first fabrication process will be described with reference to
First, a multilayer film 20 consisting of three layers of TAC, PVA, and TAC that together form the polarizing plate is produced (s1), and the film is cut to a size manageable for working (work size) (s2). Next, annealing is performed to remove the curl and slack in the film (s3), after which the process proceeds to the electrically conductive polymer coating step (s4).
In step S4, the electrically conductive polymer is applied over the surface of the multilayer film 20. Bar coating, spray coating, screen printing, etc. can be used as the coating method, and portions where the electrically conductive film need not be formed may be covered with a mask so that the electrically conductive film can be formed only on the necessary portions. The film thickness of the thus applied electrically conductive polymer is 10 μm to 30 μm before drying. The resistance value of the transparent electrically conductive film, after drying at 100 to 120° C., is 400 to 900Ω/□.
A material such as polythiophene, polyaniline, or the like is used as the transparent electrically conductive polymer. Next, the multilayer film 20 coated with the electrically conductive polymer is dried in a drier 24 at 100 to 120° C. In this way, by applying the electrically conductive polymer in the form of a solution to the multilayer film 20 and drying the solution, the electrically conductive polymer film can be easily formed (s4).
Next, Ag is printed to form the electrode pattern on the film (s5). Finally, the film is stamped out to fit the size of the touch panel (26) to complete the fabrication of the upper transparent substrate. Here, it will be recognized that the metal material for forming the circuit pattern is not limited to Ag.
The second fabrication process is a method in which, after forming the transparent electrically conductive polymer film on the protective film TAC (of the polarizing film), the protective film TAC is bonded to the polarizing film PVA. A description will be given below by referring to
In this fabrication example, the film thickness of the electrically conductive polymer was 10 μm to 30 μm before drying, and the resistance value of the transparent electrically conductive film 3 after drying was 400 to 900Ω/□. Next, the protective film with the electrically conductive polymer printed thereon (13, 3) is bonded to one surface of the polarizing film 12, and the protective film 11 with no electrically conductive polymer printed thereon is bonded to the other surface of the polarizing film 12, to complete the fabrication of the polarizing plate 8 having the electrically conductive polymer layer formed thereon. The thus fabricated polarizing plate 8 is cut to a suitable work size, followed by annealing, Ag electrode pattern printing, and film stamping, to complete the fabrication of the upper transparent substrate (not shown).
Here, prior to the printing of the electrically conductive polymer 3, the surface of the protective film 13 on which the electrically conductive polymer is to be printed may be radiated with an excimer laser to activate the surface in order to enhance the adhesion of the electrically conductive polymer to the protective film 13; by so doing, a more stable electrically conductive polymer layer can be formed.
As an alternative method, if an undercoat formed by dispersing binder particles in a transparent resin is applied as a base treatment (easy adhesion layer) for the formation of the electrically conductive polymer, the adhesion of the electrically conductive polymer further improves, and a stable electrically conductive polymer layer 3 can be formed.
The fabrication process of the glass substrate is the same as the prior art flow and, therefore, will not be described here. As earlier described, a transparent resin substrate may be used instead of the glass substrate.
In the present embodiment, since the polarizing plate is already used in the film formation step, the polarizing plate attaching step (j4) after the FPC connection can be omitted from the prior art manufacturing process.
As described above, according to the present invention, since the PET film forming process is omitted from the manufacturing process, and since the electrically conductive polymer is applied to form the electrically conductive film, not only the production cost but the time required for the production and the complexity of the production can also be reduced.
A second embodiment concerns a configuration that uses a circularly polarizing plate as the polarizing plate.
The λ/4 plate 9 does not absorb light, but changes only the phase; this is a birefringence device that introduces a phase difference of π/2 (90°) between orthogonally polarized components, and that converts linearly polarized light into circularly or elliptically polarized light or converts circularly polarized light into linearly polarized light. The coating layer 12 is formed to protect the interior of the panel, and has a thickness of 3 μm to 4 μm.
The λ/4 plate 9 can be fabricated by first depositing polycarbonate (PC) or polyvinyl alcohol (PVA) as the material in the form of a film by solvent casting, and then uniaxially stretching the film. In the second embodiment, after the λ/4 plate is coated on one surface thereof with the electrically conductive polymer by the previously described method (using a roll coater, gravure coater, bar coater, spray coater, screen printing, or the like), the λ/4 plate is bonded to the polarizing film. As an alternative method, the film made of the above material (PC or PVA) may first be coated with the electrically conductive polymer 3 and then uniaxially stretched to produce the phase retardation plate having the electrically conductive polymer film formed thereon (3, 9), and the thus produced phase retardation plate may be bonded to the polarizing plate 8 to fabricate the upper transparent substrate. Such processing is not possible with ITO which is a brittle material.
Finally, the film (8, 9, 3) and the glass substrate 4 with the ITO layer 6 and the dot spacers 5 formed thereon are bonded together along their outer edges by the double-side adhesive tape 7, to complete the construction of the panel.
According to the present invention, the upper transparent substrate of the touch panel can be fabricated in a simple process that involves applying a transparent electrically conductive polymer; since this process can be accomplished by continuous processing in the atmosphere, the production cost, the time required for the production, and the complexity of the production can be greatly reduced. Further, since the polarizing plate coated with the electrically conductive polymer is flexible and resistant to repeated bending, the life of the touch panel can be greatly increased. Furthermore, the manufacturing process is simplified as the PET film used in the prior art is omitted. Since touch panels of the resistive film type are currently in widespread use, it is apparent that the industrial applicability of the touch panel of the present invention is enormous.
Although the above embodiments have been described as exemplary embodiments of the invention, it should be understood that additional modifications, substitutions, and changes may be made to the above system without departing from the scope of the invention as disclosed herein. Accordingly, the scope of the invention is by no means restricted by the specific embodiments described herein, but should be defined by the appended claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-224103 | Aug 2006 | JP | national |
