This application is a national phase of PCT Application No. PCT/JP2014/052424 filed Feb. 3, 2014, which in turn is claims benefit of Japanese Application No. 2013-032914 filed Feb. 22, 2013 and Japanese Application No. 2013-269052 filed Dec. 26, 2013.
The present invention relates to an optically transparent electrode mainly used for touchscreens and, in particular, to an optically transparent electrode preferable for projected capacitive touchscreens.
In electronic devices, such as PDAs (personal digital assistants), 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, as its basic component, an optically transparent electrode in which an optically transparent conductive layer is provided on a base material, and does not have any movable parts. Due to high durability and high transmission, capacitive touchscreens are used in various applications. Further, projected capacitive technology allows simultaneous multipoint detection, and therefore is widely used for smartphones, tablet PCs, etc.
As optically transparent electrodes used for touchscreens, those having an optically transparent conductive layer made of ITO (indium tin oxide) formed on a base material have been commonly used. However, there has been a problem of low total light transmittance due to high refractive index and high surface light reflectivity of an optically transparent conductive layer made of ITO. Another problem is that an ITO conductive layer has low flexibility and thus is prone to crack when bent, resulting in an increased electrical resistance.
Known as an alternative to an optically transparent electrode having an optically transparent conductive layer made of ITO is an optically transparent electrode having a higher total light transmittance and a higher conductivity, the optically transparent electrode being obtainable by forming a mesh pattern of metal thin lines as an optically transparent conductive layer on an optically transparent base material, in which metal pattern, for example, the line width, pitch, pattern shape, etc. are appropriately adjusted. Regarding the pattern of the metal thin lines, it is known that a repetition unit of any shape may 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 lozenge, a parallelogram, and a trapezoid; a polygon, such as a hexagon, an octagon, a dodecagon, and an icosagon; a circle; an ellipse; and a star, and a combinational pattern of two or more thereof are used.
For the production of an optically transparent electrode using an optically transparent conductive layer consisting of metal thin lines, a semi-additive 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 for forming a conductive pattern is disclosed in, for example, Patent Literature 2, Patent Literature 3, etc.
Also, in recent years, 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 is known. For example, Patent Literature 4, Patent Literature 5, Patent Literature 6, etc. disclose a technology for forming a metal silver pattern by a pattern exposure and 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. The patterning by this method can reproduce uniform line width. In addition, due to the highest conductivity of silver among all metals, a thinner line with a higher conductivity can be achieved as compared with other methods. An additional advantage is that an optically transparent conductive layer having a metal silver pattern obtained by this method has a higher flexibility, i.e., a longer flexing life as compared with an optically transparent conductive layer made of ITO.
Generally, in a projected capacitive touchscreen, an optically transparent electrode having two optically transparent conductive layers each having a sensor part formed of a plurality of column electrodes is used as a touch sensor. In such an application, a touchscreen in which a metal pattern having a repetition unit of any shape is used as a column electrodes has a problem. That is, an operator of the touchscreen usually keeps staring at the display, and as a result tends to recognize the metal pattern itself (the metal pattern is highly visible) . Also, in the optically transparent electrode having two optically transparent conductive layers overlapped with each other, depending on the shape of the metal pattern, moire can be caused, resulting in even higher visibility. Further, in the cases of an optically transparent electrode in which the metal pattern having a repetition unit is formed of very thin metal lines, the electrical resistance value can vary depending on the pattern shape under an atmosphere of high humidity and high temperature. There has been no known method to solve the above mentioned problem of moire and the problem on the stability of electrical resistance values at the same time.
To address these problems, Patent Literature 7 proposes a method in which column electrodes with a metal pattern of which the repetition unit is in the shape of a lozenge are used for one of two optically transparent conductive layers while column electrodes with a metal pattern of which the repetition unit is the same lozenge rotated 90° are used for the other optically transparent conductive layer. However, in this method, moire maybe seen depending on conditions, and the problem of unstable electrical resistance values under an atmosphere of high humidity and high temperature is not sufficiently solved.
For example, Patent Literature 8 etc. propose a method in which a diamond-like pattern is used as the metal pattern of column electrodes, and the upper and lower optically transparent conductive materials are superposed in such a manner that the metal patterns constituting the column electrodes of the two optically transparent conductive layers never overlap with each other for solving the problem of moire. However, in this method, the two optically transparent conductive layers need to be joined with very high positional accuracy, and insufficient accuracy tends to generate portions where the upper and lower patterns mistakenly overlap with each other or where no pattern exists, leading to even higher visibility. In addition, this method inevitably generates portions with narrower width of column electrodes, and such portions are more significantly affected by the problem of unstable electrical resistance values of the above-mentioned metal pattern having a repetition unit formed of very thin metal lines under an atmosphere of high humidity and high temperature.
An object of the present invention is to provide an optically transparent electrode which has a high total light transmittance, hardly produces moire, and has an excellent stability of electrical resistance values and therefore is suitable as an optically transparent electrode for capacitive touchscreens.
The above object of the present invention is basically achieved by an optically transparent electrode having, on an optically transparent base material, at least two optically transparent conductive layers having a sensor part electrically connected to a terminal part and a dummy part not electrically connected to the terminal part, the sensor part and the dummy part each having a repetition unit metal pattern of a predetermined shape, the sensor part of one of the optically transparent conductive layers being formed of a plurality of column electrodes extending in a first direction, the column electrodes and the dummy parts being arranged in an alternating manner, the sensor part of the other optically transparent conductive layer being formed of a plurality of column electrodes which extend in a second direction perpendicular to the first direction and are arranged alternately with the dummy parts, the optically transparent electrode satisfying all of the following requirements (a) to (c).
k1>j1 (a)
Here, k1 denotes the average length in the first direction of the predetermined unit metal pattern of the column electrodes extending in the first direction of one of the optically transparent conductive layers, and j1 denotes the average length in the second direction of the same predetermined unit metal pattern.
2M=n×j1 (b)
Here, M denotes the average center-to-center distance of the column electrodes extending in the first direction, and n denotes a natural number.
k2<j2; (c)
and neither k1/j2 nor j2/k1 is a natural number.
Here, k2 denotes the average length in the first direction of the predetermined unit metal pattern of the column electrodes extending in the second direction of the other optically transparent conductive layer, and j2 denotes the average length in the second direction of the same predetermined unit metal pattern.
Preferably, the following requirement (d) is satisfied.
2L=p×k2 (d)
Here, L denotes the average center-to-center distance of column electrodes of the other optically transparent conductive layer, the column electrodes extending in the second direction, and p denotes a natural number.
Preferably, the following requirement (e) is satisfied.
2L=q×k1 (d)
Here, q denotes a natural number.
Preferably, a requirement of 0.1×k1<j1<0.7×k1 is satisfied, and more preferably, a requirement of 0.35×k1<j1<0.6×k1 is satisfied. Preferably, a requirement of 0.15×j2<k2<0.7×j2 is satisfied, and more preferably, a requirement of 0.35×j2<k2<0.6×j2 is satisfied.
In an optically transparent conductive layer, the predetermined unit metal pattern shape of the sensor part and the predetermined unit metal pattern shape of the dummy part are preferably congruent. Preferably, the predetermined unit metal pattern shape is a lozenge, and the diagonals thereof are in the first direction and in the second direction (perpendicular to the first direction).
The present invention can provide an optically transparent electrode which has a high total light transmittance, hardly produces moire, and has an excellent stability of electrical resistance values and therefore is suitable as an optically transparent electrode for capacitive touchscreens.
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 thereto and various alterations and modifications may be made without departing from the technical scope of the invention.
As described above, the optically transparent electrode of the present invention has two optically transparent conductive layers (2a and 2b in
The optically transparent electrode 20 shown in
Also, in the present invention, it is possible to combine optically transparent conductive materials by a production method other than the above-mentioned methods, and to use, as an additional layer, a publicly known optical film, such as a hard coat film, an antireflection film, and an electromagnetic shielding film.
It is preferred to use, as protective base materials 3 and 5 shown in
In
As the adhesive layer 4 which the optically transparent electrode 20 shown in
In the present invention, the positional relationship between the two optically transparent conductive layers is particularly important, and as long as the positional relationship between the optically transparent conductive layers 2a and 2b satisfies the requirements described below, similar effects can be obtained with the configuration shown in
In the present invention, the sensor part 11 may be electrically connected by direct contact with the terminal part 15, but is preferably electrically connected with the terminal part 15 via the wiring part 14 as shown in
The column electrode 6a composing the sensor part 11 in the optically transparent conductive layer 2a is connected, via a wiring part 14, to a terminal part 15. By connecting the terminal part 15 to the outside, the changes in capacitance detected by the sensor part 11 can be captured. Meanwhile, metal patterns not electrically connected to the terminal part 15 all serve as dummy parts in the present invention. In the present invention, the wiring part 14 and the terminal part 15 need not particularly have optical transparency, and therefore may either be a solid pattern without spaces or be optically transparent as the column electrodes 6a are.
In the optically transparent conductive layer 2a in
In
The value of M as the average center-to-center distance of the column electrodes 6a may be set as desired at the time of designing the pattern, and may be confirmed as follows: a line passing the center of the width of a column electrode in the x direction is determined as the center line; regarding all the combinations of two column electrodes adjacent to each other, distances between the center lines are determined; and the arithmetic average thereof is calculated. In the calculation of the arithmetic average of the distances between the center lines, 10% of greater deviation may be excluded from the population.
In
As mentioned above, there must be no electrical conduction between the column electrodes 6a constituting the sensor part and the metal patterns 16 constituting the dummy parts. The method for breaking electrical conduction may by any method, and examples thereof include a method in which parts of the metal patterns 16 are provided with line breaks as shown in
The optically transparent electrode of the present invention needs to satisfy all of the following requirements (a) to (c).
j1<k1 (a)
2M=n×j1 (b)
(n is a natural number)
k2<j2; (c)
and neither k1/j2 nor j2/k1 is a natural number.
Further, the following requirement (d) is preferably satisfied to achieve the object of the present invention.
2L=p×k2 (d)
(p is a natural number)
Also, the following requirement (e) is preferably satisfied to achieve the object of the present invention.
2L=q×k1 (e)
(q is a natural number)
When these requirements are satisfied, an optically transparent electrode which is more excellent in the stability of electrical resistance values can be obtained.
Regarding the relation between k1 and j1, the following requirement is preferably satisfied. Preferably 0.15×k1<j1<0.7×k1, and more preferably 0.35×k1<j1<0.6×k1. Also, regarding the relation between k2 and j2, the following requirement is preferably satisfied. Preferably 0.15×j2<k2<0.7×j2, and more preferably 0.35×j2<k2<0.6×j2. When these requirements are satisfied, an optically transparent electrode which is more excellent in the stability of electrical resistance values can be obtained.
The optically transparent electrode of the present invention may be provided with, in addition to the two optically transparent conductive layers described above, a publicly known layer, such as a hard coating 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 unless it goes beyond the technical scope thereof.
As an optically transparent base material, a 100-μm-thick polyethylene terephthalate film was used. The total light transmittance of this optically transparent base material was 91%.
Next, in accordance with the following formulation, a physical development nuclei coating liquid was prepared, applied onto one side of the optically transparent base material, and dried to provide a physical development nuclei layer.
<Preparatian of Palladium Sulfide Sol>
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.
<Preparation of Physical Development Nuclei Coating Liquid>
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 liquid 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 contained silver halide composed of 95 mol % of silver chloride and 5 mol % of silver bromide and had 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.
<Composition of Intermediate Layer/Per m2 of Silver Halide Photosensitive Material>
Dye 1
<Composition of Silver Halide Emulsion Layer/Per m2 of Silver Halide Photosensitive Material>
<Composition of Protective Layer/Per m2 of Silver Halide Photosensitive Material>
The silver halide photosensitive material obtained as above was brought into close contact with a transparent manuscript having the pattern shown in
After the silver halide photosensitive material was immersed 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, optically transparent conductive materials each having a metal silver image having the pattern of
<Composition of Diffusion Transfer Developer>
Water was added to make the total volume of 1000 mL, and the pH was adjusted to 12.2.
The obtained two optically transparent conductive materials and a 2-mm thick polycarbonate board (made by Mitsubishi Gas Chemical Co., Inc., hereinafter abbreviated to PC board) were joined together with use of an optical adhesive tape (MHM-FW25 made by NICHIEIKAKOH CO., LTD. hereinafter abbreviated to OCA), so that the optically transparent conductive layer side of each of the two optically transparent conductive materials faces the PC board side, that alignment marks (+) at the four corners overlap, and that the OCA is used only in the rectangular area surrounded by the imaginary dashed line in
The same procedure was performed as in Example 1 except that transparent manuscripts in which the values of k1, j1, and angle 1 in
The obtained optically transparent electrodes of Examples 1 to 3, and Comparative Examples 1 to 5 were evaluated for the occurrence of moire, the total light transmittance, and the stability of electrical resistance values by the method shown below. The results are shown in Table 1.
<Occurrence of Moire>
The obtained optically transparent electrode was placed on the screen of a 23″ wide LCD monitor (RDT234WK (BK) made by Mitsubishi Electric) displaying solid white, and was evaluated based on the following criteria. Poor and Very Poor are not practically acceptable.
Fair: Moire was not confirmed by visual inspection.
Poor: Moire was confirmed by careful visual inspection.
Very Poor: Moire was clearly confirmed by visual inspection.
<Total Light Transmittance>
The obtained optically transparent electrode was measured for the total light transmittance of the portion in which the two optically transparent conductive materials and the PC board were joined with use of the OCA, with use of a haze meter (HZ-2 made by Suga Test Instruments Co., Ltd.).
<Stability of Electrical Resistance Values>
The above test results were evaluated based on the following criteria. 1 and 2 are not practically acceptable.
5: The index of the stability of electrical resistance values is less than 5%, and no column electrodes have line break.
4: The index of the stability of electrical resistance values is 5% or more and less than 10%, and no column electrodes have line break.
3: The index of the stability of electrical resistance values is 5% or more and less than 10%, and a part of column electrodes have line break.
2: The index of the stability of electrical resistance values is 10% or more, and a part of column electrodes have line break.
1: The index of the stability of electrical resistance values is significantly high, and all the column electrodes have line break.
The results in Table 1 show that the present invention provides an optically transparent electrode which has a high total light transmittance, hardly produces moire, and has an excellent stability of electrical resistance values and therefore is suitable as an optically transparent electrode for capacitive touchscreens.
Number | Date | Country | Kind |
---|---|---|---|
2013-032914 | Feb 2013 | JP | national |
2013-269052 | Dec 2013 | JP | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/JP2014/052424 | 2/3/2014 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2014/129298 | 8/28/2014 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
20090277672 | Matsumoto | Nov 2009 | A1 |
20110291966 | Takao et al. | Dec 2011 | A1 |
20120133622 | Brokken et al. | May 2012 | A1 |
20120268418 | Ishizaki et al. | Oct 2012 | A1 |
20130294037 | Kuriki et al. | Nov 2013 | A1 |
20140063374 | Kuriki | Mar 2014 | A1 |
Number | Date | Country |
---|---|---|
H10-41682 | Feb 1998 | JP |
2003-077350 | Mar 2003 | JP |
2005-250169 | Sep 2005 | JP |
2007-188655 | Jul 2007 | JP |
2007-287953 | Nov 2007 | JP |
2007-287994 | Nov 2007 | JP |
2011-248722 | Dec 2011 | JP |
2012-033147 | Feb 2012 | JP |
2012-226687 | Nov 2012 | JP |
2012-243119 | Dec 2012 | JP |
2013-501992 | Jan 2013 | JP |
2012099150 | Jul 2012 | WO |
Number | Date | Country | |
---|---|---|---|
20150378477 A1 | Dec 2015 | US |