The present invention relates to an optically transparent conductive material mainly used for touchscreens and, in particular, to an optically transparent conductive material preferably used for optically transparent electrodes of projected capacitive touchscreens.
In electronic devices, such as personal digital assistants (PDAs), laptop computers, office automation equipment, medical equipment, and car navigation systems, touchscreens are widely used as their display screens that also serve as input means.
There are a variety of touchscreens that utilize different position detection technologies, such as optical, ultrasonic, surface capacitive, projected capacitive, and resistive technologies. A resistive touchscreen has a configuration in which an optically transparent conductive material and a glass plate with a transparent conductive layer are separated by spacers and face each other. A current is applied to the optically transparent conductive material and the voltage of the glass plate with a transparent conductive layer is measured. In contrast, a capacitive touchscreen has a basic configuration in which a touch sensor formed of an optically transparent electrode is an optically transparent conductive material having a transparent conductive layer provided on a base material. Not having any movable parts, the capacitive touchscreen has high durability and high transmission, and therefore are used in various applications. Further, a touchscreen utilizing projected capacitive technology allows simultaneous multipoint detection, and therefore is widely used for smartphones, tablet PCs, etc.
As an optically transparent conductive material used for touchscreens, those having an optically transparent conductive layer made of an ITO (indium tin oxide) film formed on a base material have been commonly used. However, there has been a problem of low optical transparency due to high refractive index and high surface light reflectivity of ITO conductive films. Another problem is that ITO conductive films have low flexibility and thus are prone to crack when bent, resulting in increased electric resistance of the optically transparent conductive material.
Known as an alternative to an optically transparent conductive material having an ITO conductive film is an optically transparent conductive material having a mesh pattern of a metal thin line on an optically transparent base material, in which pattern, for example, the line width, pitch, pattern shape, etc. are appropriately adjusted. This technology provides an optically transparent conductive material which maintains a high light transmittance and which has a high conductivity. Regarding the mesh pattern formed of metal thin lines (hereinafter written as metal mesh pattern), it is known that a repetition unit of any shape can be used. For example, in Patent Literature 1, a triangle, such as an equilateral triangle, an isosceles triangle, and a right triangle; a quadrangle, such as a square, a rectangle, a rhombus, a parallelogram, and a trapezoid; a (equilateral) n-sided polygon, such as a (equilateral) hexagon, a (equilateral) octagon, a (equilateral) dodecagon, and a (equilateral) icosagon; a circle; an ellipse; and a star, and a combinational pattern of two or more thereof are disclosed.
As a method for producing the above-mentioned optically transparent conductive material having a metal mesh pattern, a semi-additive method for forming a metal mesh pattern, the method comprising making a thin catalyst layer on a base material, making a resist pattern on the catalyst layer, making a laminated metal layer in an opening of the resist by plating, and finally removing the resist layer and the base metal protected by the resist layer, is disclosed in, for example, Patent Literature 2 and Patent Literature 3. Also, in recent years, as a method for producing the optically transparent conductive material having a metal mesh pattern, a method in which a silver halide diffusion transfer process is employed using a silver halide photosensitive material as a precursor to a conductive material has been known.
For example, Patent Literature 4, Patent Literature 5, and Patent Literature 6 disclose a technology for forming a metal (silver) mesh pattern by a reaction of a silver halide photosensitive material (a conductive material precursor) having a physical development nucleus layer and a silver halide emulsion layer in this order on a base material with a soluble silver halide forming agent and a reducing agent in an alkaline fluid. This method allows formation of a metal mesh pattern of a uniform line width made of silver, the most conductive metal, and thus the mesh pattern has a thinner line and a higher conductivity as compared with those obtained by other methods. An additional advantage is that a conductive layer having a metal mesh pattern obtained by this method has a higher flexibility, i.e. a longer flexing life as compared with an ITO conductive layer.
In a touchscreen application, an optically transparent conductive material is placed over a liquid crystal display, the cycle of the metal mesh pattern and the cycle of the liquid crystal display element interfere with each other, causing a problem of moire. In recent years, liquid crystal displays having elements of various resolutions are used, which further complicates the problem.
As a solution to this problem, in Patent Literature 7, Patent Literature 8, Patent Literature 9, and Patent Literature 10, a method in which the interference is suppressed by the use of a traditional metal mesh pattern of random shape described in, for example, Non Patent Literature 1 is suggested. In Patent Literature 11, an electrode base material for touchscreens, in which a plurality of unit pattern areas having a random shape metal mesh pattern are arranged is introduced.
Patent Literature 1: JP 10-41682 A
Patent Literature 2: JP 2007-287994 A
Patent Literature 3: JP 2007-287953 A
Patent Literature 4: JP 2003-77350 A
Patent Literature 5: JP 2005-250169 A
Patent Literature 6: JP 2007-188655 A
Patent Literature 7: JP 2011-216377 A
Patent Literature 8: JP 2013-37683 A
Patent Literature 9: JP 2014-41589 A
Patent Literature 10: JP-2013-540331 T
Patent Literature 11: JP 2014-26510 A
Non Patent Literature 1: Mathematical Model of Territories—Introduction to Mathematical Engineering through Voronoi diagrams—(published by Kyoritsu Shuppan in February, 2009)
Since the above metal mesh pattern of random shape does not have any cyclic pattern shape formed by repetition of a simple unit graphic and therefore theoretically does not interfere with the cycle of the liquid crystal display element, moire does not occur. However, in the metal mesh pattern, a part where the distribution of the metal thin line is sparse and a part where the distribution is dense randomly appear, which is visibly recognized as a grain-like pattern, causing a problem of so-called “grain”.
In the cases where the optically transparent electrode of a capacitive touchscreen is formed of a metal mesh pattern, a plurality of sensor parts extending in a specific direction are formed of a metal mesh pattern, and are electrically connected with a terminal part via a wiring part. Meanwhile, between the plurality of sensor parts, for the purpose of lowering the visibility of the sensor parts, dummy parts formed of a metal mesh pattern are provided. The metal mesh pattern of the dummy parts has line breaks to avoid electrical connection between separate sensor parts. However, in certain kinds of touchscreens, the width of each sensor part extending in a specific direction is designed so narrow as to be almost equal to the interval between the lines of the metal mesh pattern. In such cases, if the line width of the metal mesh pattern is too thin, the reliability of the optically transparent conductive material may decrease due to the occurrence of changes in the resistance value or line breaks during the processing of the touchscreen or the storage of the optically transparent conductive material having the metal mesh pattern under high-temperature and high-pressure conditions. This problem may be further worsened in the above-mentioned optically transparent conductive material having a random metal mesh pattern. The electrode base material for touchscreens described in the above Patent Literature 11 also has a similar problem regarding the reliability, and has a problem of further worsen visibility of the grain etc. as compared with a non-repetitive pattern.
An object of the present invention is to provide an optically transparent conductive material which is suitable as an optically transparent electrode for capacitive touchscreen, the optically transparent conductive material having a favorably low visibility of moire and grain even when placed over a liquid crystal display and having a high reliability.
According to the present invention, the above object will be basically achieved by (1) an optically transparent conductive material having, on an optically transparent base material, sensor parts electrically connected to terminal parts and dummy parts not electrically connected to the terminal parts, the conductive material being characterized in that in the plane of the optically transparent conductive layer, the sensor parts are formed of a plurality of column electrodes extending in a first direction, the plurality of column electrodes being arranged at an arbitrary cycle in a second direction perpendicular to the first direction in such a manner that each dummy part is sandwiched between every two of the sensor parts, and that the sensor parts and/or the dummy parts are formed of a metal pattern in which a unit pattern area having any of the following mesh patterns (a) to (c) is repeated in at least two directions in the plane of the optically transparent conductive layer.
(a) A mesh pattern consisting of Voronoi edges formed in relation to a plurality of points (generators) arranged in a plane tiled using polygons, the mesh pattern being characterized in that each polygon has only one generator arranged in the polygon, and the generator is at an arbitrary position within a reduced polygon formed by connecting points at 90% of the direct distance from the center of gravity of the polygon to each vertex of the polygon.
(b) A mesh pattern formed by non-periodic tiling of a plane using polygons, the mesh pattern being characterized in that the length of the longest side of all the sides of all the polygons is not more than ⅓ of the cycle of the sensor parts in the second direction.
(c) A mesh pattern obtained by moving 50% or more of all the intersections in an original graphic formed of repetition of an original unit graphic consisting of a polygon (50% or more of all the vertices of the original unit graphics) in a direction, the mesh pattern being characterized in that the distance between the original position of an intersection before the move and the position of the intersection after the move is less than ½ of the distance from the center of gravity of the original unit graphic to the closest vertex of the original unit graphic.
(2) The above object will be achieved by the optically transparent conductive material of the above (1), characterized in that the repetition cycle of the unit pattern area in the second direction is equal to an integral multiple of the column cycle in the second direction, of the column electrodes extending in the first direction; or the column cycle in the second direction, of the column electrodes extending in the first direction is equal to an integral multiple of the repetition cycle of the unit pattern area in the second direction.
(3) The above object will be achieved by the optically transparent conductive material of the above (1) or (2), characterized in that the repetition cycle of the unit pattern area in the first direction is equal to an integral multiple of the pattern cycle in the first direction, of the column electrodes extending in the first direction; or the pattern cycle in the first direction, of the column electrodes extending in the first direction is equal to an integral multiple of the repetition cycle of the unit pattern area in the first direction.
The present invention can provide an optically transparent conductive material which has a favorably low visibility of moire and grain even when placed over a liquid crystal display and which has a high reliability.
Hereinafter, the present invention will be illustrated in detail with reference to drawings, but it is needless to say that the present invention is not limited to the embodiments described below and various alterations and modifications may be made without departing from the technical scope of the invention.
In
In the present invention, the sensor part and/or the dummy part is formed of a metal mesh pattern formed of repetition of a unit pattern area having a random mesh pattern. Hereinafter, the unit pattern area having a random mesh pattern used in the optically transparent conductive material of the present invention will be described. The mesh pattern used in the present invention includes the following type (a), type (b), and type (c). The use of any one of these mesh patterns gives a random mesh pattern of the sensor part and/or the dummy part, in a unit pattern area having a certain area dimension.
The most preferable mesh pattern used in the present invention is a Voronoi diagram (type a). The Voronoi diagram is a publicly known diagram applied in various fields including the field of information processing.
In the Voronoi diagram type of the present invention, in a graphic formed by tiling of a plane using polygons, each polygon has only one generator arranged in the polygon. Also, the generator is located at an arbitrary position within a reduced polygon formed by connecting points at 90% of the direct distance from the center of gravity of the polygon to each vertex of the polygon.
A different mesh pattern used in the present invention may be a non-cyclic tiling diagram (type b) formed by non-periodic tiling of a plane using polygons. The method used for non-periodic tiling of a plane using polygons may be a publicly known method. Such publicly known methods include, for example, the method using a Penrose tiling devised by Roger Penrose, in which method two kinds of rhombuses, i.e., a rhombus having an acute angle of 72° and an obtuse angle of 108° and a rhombus having an acute angle of 36° and an obtuse angle of 144° are used in combination; a method for non-periodic tiling of a plane using a square, a equilateral triangle, and a parallelogram having angles of 30° and 150° ; and a method for non-periodic tiling of a plane using a “girth” pattern used as a design in the medieval Islamic world. Each side in the non-periodic tiling diagram is preferably a straight line but may be a curved line, a wavy line, a zigzag line, etc. unless the basic shape of the diagram is significantly altered. The length of the longest side (in the cases where a wavy line or a curved line is used, the distance between vertices is regarded as the side) of the sides of all the polygons used in the non-periodic tiling of a plane is not more than ⅓ of the cycle (the cycle in the y-direction in
Another mesh pattern used in the present invention may be a random mesh (type c) formed by randomly moving the vertices of a commonly used regular mesh. Hereafter, the random mesh will be illustrated using
Hereafter, the method for moving the vertices from their original positions in an original graphic will be described.
In
Moving the vertices of the original unit graphic 32 in the above-described manner and then connecting the moved vertices results in the graphic shown in
In the present invention, the sensor part 11 and the dummy part 12 in
In
As already described in the description of
In
Thus far, an optically transparent conductive material which has sensor parts extending in the x direction has been described. In the optically transparent electrode of a capacitive touchscreen, this optically transparent conductive material and an optically transparent conductive material which has sensor parts extending in the y direction are used as a pair in a layered manner, and the sensor parts extending in the y direction are arranged at an arbitrary cycle in the x direction. When the column cycle of the sensor parts extending in the y direction is referred to as “column cycle 64”, the column cycle 64 is preferably equal to the pattern cycle 62 of the sensor parts 11 in
In the present invention, the metal pattern constituting the sensor part 11, the dummy part 12, the peripheral wiring part 14, the terminal part 15, etc. in
As the optically transparent base material 2 illustrated in
The optically transparent conductive material of the present invention may be provided with, in addition to the optically transparent conductive layer described above, a publicly known layer, such as a hard coat layer, an antireflection layer, an adhesive layer, and an antiglare layer at any location. Also, between the optically transparent base material and the optically transparent conductive layer, a publicly known layer, such as a physical development nuclei layer, an easily adhering layer, and an adhesive layer may be provided.
Hereinafter, the present invention will be illustrated in more detail by Examples, but the present invention is not limited thereto and can be embodied in various ways within the technical scope of the invention.
As an optically transparent base material, a 100-μm-thick polyethylene terephthalate film was used. The total light transmittance of this base material was 91%.
Next, in accordance with the following formulation, a physical development nuclei coating liquid was prepared, applied onto the optically transparent base material, and dried to provide a physical development nuclei layer.
Liquid A and Liquid B were mixed with stirring for 30 minutes, and then passed through a column filled up with an ion exchange resin to give a palladium sulfide sol.
Subsequently, an intermediate layer, a silver halide emulsion layer, and a protective layer, of which the compositions are shown below, were applied in this order (from closest to the optically transparent base material) onto the above physical development nuclei layer, and dried to give a silver halide photosensitive material. The silver halide emulsion was produced by a general double jet mixing method for photographic silver halide emulsions. The silver halide emulsion was prepared using 95 mol% of silver chloride and 5 mol% of silver bromide so as to have an average particle diameter of 0.15 μm. The obtained silver halide emulsion was subjected to gold and sulfur sensitization using sodium thiosulfate and chloroauric acid by the usual method. The silver halide emulsion obtained in this way contained 0.5 g of gelatin per gram of silver.
Dye 1
The silver halide photosensitive material obtained as above was brought into close contact with a transparent manuscript having the pattern image shown in
After immersion in the diffusion transfer developer shown below at 20° C. for 60 seconds, the silver halide emulsion layer, the intermediate layer, and the protective layer were washed off with warm water at 40° C., and a drying process was performed.
In this way, the optically transparent conductive material 1 having a metal silver image having the pattern of
Water was added to the above ingredients to make the total volume of 1000 mL, and the pH was adjusted to 12.2.
The same procedure was performed as in the preparation for the optically transparent conductive material 1 except for using a transparent manuscript having the pattern of
The same procedure was performed as in the preparation for the optically transparent conductive material 1 except for using a transparent manuscript having the pattern of
The same procedure was performed as in the preparation for the optically transparent conductive material 1 except for using a transparent manuscript which has the pattern of
The same procedure was performed as in the preparation for the optically transparent conductive material 1 except for using a transparent manuscript which has the pattern of
The same procedure was performed as in the preparation for the optically transparent conductive material 1 except for using a transparent manuscript which has the pattern of
The obtained optically transparent conductive materials 1 to 6 were evaluated in terms of the visibility and the reliability (stability of resistance). The results are shown in Table 1. The obtained optically transparent conductive material was placed on the screen of a 23″ wide LCD monitor (Flatron23EN43V-B2 made by LG Electronics) displaying solid white, and the visibility was evaluated based on the following criteria. The level at which moire and grain was obvious was defined as “C”, the level at which the boundary was noticeable as a result of close inspection was defined as “B”, and the level at which the boundary was unnoticeable was defined as “A”. For the evaluation of reliability (stability of resistance), each optically transparent conductive material was left in the environment of a temperature of 85° C. and a relative humidity of 95% for 600 hours, then the continuity between all the pairs of terminal parts 15 in
Table 1 shows that the present invention can provide an optically transparent conductive material which has a favorably low visibility of moire and grain even when placed over a liquid crystal display and which has an excellent reliability (stability of resistance).
Number | Date | Country | Kind |
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2014-090916 | Apr 2014 | JP | national |
This application is a divisional of application Ser. No. 15/303,605 filed Oct. 12, 2016, which in turn is a National Phase of PCT Application No. PCT/JP2015/062231 filed Apr. 22, 2015, which in turn claims benefit of Japanese Application No. 2014-090916 filed Apr. 25, 2014.
Number | Date | Country | |
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Parent | 15303605 | Oct 2016 | US |
Child | 15926329 | US |