Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Reexamination Certificate
2001-04-24
2004-02-10
Jones, Deborah (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
C428S336000, C428S402000, C428S702000, C428S689000, C428S156000, C428S220000, C428S323000
Reexamination Certificate
active
06689458
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a transparent conductive laminate and to a touch panel which uses the transparent conductive laminate and has excellent durability and excellent visibility.
BACKGROUND OF THE INVENTION
Recently, the wide employment of portable information-processing equipment on which a liquid crystal display for displaying information and a touch panel (called a switch panel, a membrane switch or a tablet) for inputting information were loaded was started. Most of the touch panels are resistant film type ones. Each of the resistant film type touch panel is formed by facing two transparent electrode substrates having transparent conductive layers formed thereon, respectively, each other at a distance of 10 to 100 &mgr;m. Both the transparent electrode substrates are brought into contact with each other only at a site touched by a finger, a pen, or the like, to act as a switch. For example, the selection of a menu on a display screen, the inputting of a handwritten figure, handwritten letters, or so on, can be carried out. As the transparent electrode substrates, ones manufactured by disposing the transparent conductive layers of a metal oxide such as indium tin oxide (ITO) or tin oxide containing antimony or the like on substrates such as glass substrates or various kinds of transparent polymer substrates are widely used.
In the touch panel, the transparent electrode substrate on the side to be touched by the finger, the pen, or the like (movable electrode substrate), is preferable to be flexible from a point that the figure, letters, or the like, can easily be inputted. As the movable electrode substrate, an electrode substrate obtained by disposing a transparent conductive layer on a transparent polymer film substrate or a transparent polymer sheet substrate is usually used. There has been a problem that, when a flexible transparent electrode substrate is used as a movable electrode substrate, the movable electrode substrate is loosened due to the changes of temperature and humidity, resulting in the generation of interference fringes between the movable electrode substrate and the facing fixed electrode substrate to give an indistinct screen. There has also been a problem that, when both the surface of a movable electrode substrate and the surface of a fixed electrode substrate are extremely flat, the electrode surface of the movable electrode substrate and the electrode surface of the fixed electrode substrate are adhered to each other to cause the failure in the operation of the touch panel.
In order to solve the problems, the present inventors proposed a method for making the surface of an electrode with micro bumps. In JP-A No. 8-216327 (1996) (hereunder, JP-A means Japanese unexamined patent publication) is described a touch panel that the generation of interference fringes was controlled by using a transparent conductive laminate whose transparent conductive layer surface has a central surface average roughness (SRa) of 0.05 to 0.40 &mgr;m. In JP-A No. 10-24516 (1998) is also described a transparent conductive laminate which uses silicone resin fine particles having an average particle diameter of 4.5 &mgr;m and has an excellent slipping property and whose transparent conductive layer surface has a central surface average roughness (SRa) of 0.003 to 0.04 &mgr;m. Thereby, the problems of the generation of interference fringes and of the mutual adhesion of electrode surfaces were solved, but writing durability was often insufficient. Namely, when a test for the writing durability was carried out, it was found that the peeling of the transparent conductive layer was sometimes caused on the peripheries of the electrode surface bumps of a movable electrode substrate, resulting in the deterioration of the inputting performance of the touch panel (for example, the generation of misprinting, the insufficient accuracy of position detection) after the test of the writing durability.
On the other hand, a transparent conductive laminate in which a coating layer containing fine particles was disposed between a transparent plastic film and a transparent conductive layer was proposed for improving the writing durability (JP-A No. 10-249975 (1998)). According to the description of the patent publication, the damages of the transparent conductive layer were concentrated at extremely small areas around the apexes of bumps, because the bumps were distributed on the surface of the electrode at a proper density. Consequently, even when the transparent conductive layer was damaged, the total resistance of the transparent conductive layer was largely not changed, and the accuracy of position detection was scarcely changed. Further, the good average particle diameter of fine particles contained in the coating layer was in the range of from not less than the thickness of the coating layer to three times or less than that of the coating layer, and the good density of the particles was 10,000 to 500,000 particles/cm
2
(100 to 5,000 particles/mm
2
). However, the examinations of the present inventors showed that the writing durability was always not improved, even when the density of the particles was set to the range.
Further, in JP-A No. 10-323931 (1998) is described a transparent conductive laminate in which a coating layer containing particles having an average particle diameter of 1.0 to 4 &mgr;m at a number-average density of 500 to 3,000 particles/mm
2
and a transparent conductive layer were successively formed on a transparent plastic film to control the generation of interference fringes. However, the transparent conductive layer surface of the laminate had a ten point height (Rz) of 0.3 to 1.0 &mgr;m or larger, therefore comprised bumps of large dispersion of height, and the writing durability of the laminate was insufficient, when used as a touch panel.
A main object of the present invention is to provide a transparent conductive laminate suitable for giving a touch panel having excellent writing durability.
Another object of the present invention is to provide a touch panel which has good writing durability and excellent visibility.
DISCLOSURE OF THE INVENTION
The present inventors have paid attentions on the heights of bumps on the surface of a transparent conductive layer and have researched to solve the above-mentioned problems and obtain the touch panel which scarcely generates interference fringes and has excellent visibility giving clear letters and excellent writing durability.
Consequently, the present inventors ascertained that the writing durability did essentially not depend on the density of fine particles and that the existence of bumps, which are higher than a certain height, especially caused a problem, when the surface of a transparent conductive layer used as the electrode of the touch panel had high bumps and low bumps in a mixed state especially of large dispersion of height.
On the other hand, since adhesivity between the transparent conductive layer and a substrate such as a polymer film was also important for dynamic mechanical durability called the writing durability, the present inventors further repeatedly researched the point. It was consequently found that a peeling was caused between the transparent conductive layer and a layer containing fine particles, when the layer containing fine particles was disposed just under the transparent conductive layer in a state directly contacted with the transparent conductive layer. The inventors also examined the point and in consequence found out that it was important to control the height of bumps and the density of bumps in the layer containing fine particles and that it was extremely effective to dispose a cross-linked polymer layer between the layer containing fine particles and the transparent conductive layer in a state contacted with the transparent conductive layer.
The present invention was completed by repeating the researches on the basis of the knowledge. Namely, the present invention relates to the transparent conductive laminate which is obtained by controlling the heigh
Hara Hiroshi
Kon Tatsuichiro
Mikoshiba Hitoshi
Yahata Kazuo
Bass Wendy
Jones Deborah
Rader & Fishman & Grauer, PLLC
Teijin Limited
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