Conductive sheet, touch panel, display device, method for producing conductive sheet, and recording medium

• US 9,541,785 B2
• Filed: 04/04/2014
• Issued: 01/10/2017
• Est. Priority Date: 10/05/2011
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Iwami, Kazuchika
• Primary Examiner(s): POLO, GUSTAVO D
• Application Number:
  US14/245,831
• Publication Number:
  US 20140218642A1
• Time in Patent Office: 1,012 Days
• Field of Search: 349/12
• US Class Current: 1/1
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G06F 2203/04112 Electrode mesh in capacitive digitiser: electrode for touch sensing is formed of a mesh of very fine, normally metallic, interconnected lines that are almost invisible to see. This provides a quite large but transparent electrode surface, without need for ITO or similar transparent conductive material
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact
• CPC Class Codes: G06T 2207/30121 CRT, LCD or plasma display
• CPC Class Codes: G06T 2207/30141 Printed circuit board [PCB]
• CPC Class Codes: G06T 7/0004 Industrial image inspection
• CPC Class Codes: H05K 1/0296 Conductive pattern lay-out details not covered by sub groups H05K1/02 - H05K1/0295 H05K1/11 takes precedence; lay-out adapted to mounted component configuration H05K1/18
• CPC Class Codes: H05K 3/12 using thick film techniques, e.g. printing techniques to apply the conductive material or similar techniques for applying conductive paste or ink patterns

Abstract

The conductive sheet according to the present invention includes a base and a conductive portion that is formed on at least one main surface of the base and is formed from a plurality of thin metal wires, where a mesh pattern in which different mesh shapes are arrayed in plan view is formed by the conductive portion, and the mesh pattern is configured such that, in a power spectrum of a two-dimensional distribution of centroid positions of the mesh shapes, an average intensity on a higher spatial frequency band side than a predetermined spatial frequency is larger than an average intensity on a lower spatial frequency band side than the predetermined spatial frequency. The conductive sheet can reduce the granular feeling of noise due to pattern which the conductive sheet has and greatly improve the visibility of an object for observation.

Claims

1. A conductive sheet, comprising:

a base; and

a conductive portion that is formed on at least one main surface of the base and is formed from a plurality of thin metal wires, wherein

a mesh pattern in which different mesh shapes are arrayed in plan view is formed by the conductive portion, and

the mesh pattern is configured so

that a two-dimensional power spectrum of a centroid position distribution of the mesh shapes is given, such that an average intensity on a spatial frequency band side higher than a predetermined spatial frequency is larger than an average intensity on a spatial frequency band side lower than the predetermined spatial frequency, and

that a centroid position distribution of the mesh shapes is given such that, a root mean square deviation of each centroid positions of the mesh shapes which are disposed along a predetermined direction with respect to a direction perpendicular to the predetermined direction is equal to or greater than 15 μ

m and equal to or less than 65 μ

m.

2. The conductive sheet according to claim 1, wherein the predetermined spatial frequency is a spatial frequency at which visual response characteristics of human are equivalent to 5% of a maximum response.

3. The conductive sheet according to claim 2,

wherein the visual response characteristics of human are visual response characteristics obtained based on a Dooley-Shaw function at a distance of distinct vision of 300 mm, and

the predetermined spatial frequency is 6 cycles/mm.

4. The conductive sheet according to claim 1, wherein the predetermined spatial frequency is a spatial frequency at which a value of the two-dimensional power spectrum is maximized.

5. The conductive sheet according to claim 1, wherein each of the mesh shapes is a polygonal shape.

6. The conductive sheet according to claim 5, wherein each of the mesh shapes is determined in accordance with a Voronoi diagram based on a plurality of positions in a planar region.

7. The conductive sheet according to claim 5, wherein each of the mesh shapes is determined in accordance with a Delaunay diagram based on a plurality of positions in a planar region.

8. The conductive sheet according to claim 1, wherein the mesh pattern is formed by arraying the mesh shapes without a space.

9. The conductive sheet according to claim 1, wherein the mesh pattern includes repeated shapes.

10. The conductive sheet according to claim 1,

wherein the conductive portion includes a first conductive portion, which is formed on one main surface of the base and is formed from a plurality of thin metal wires, and a second conductive portion, which is formed on the other main surface of the base and is formed from a plurality of thin metal wires, and

the mesh pattern is formed by combining the first and second conductive portions.

11. The conductive sheet according to claim 10, further comprising:

a first protective layer that is provided on the one main surface and covers the first conductive portion; and

a second protective layer that is provided on the other main surface and covers the second conductive portion,

wherein a relative refractive index of the base with respect to the first protective layer and/or a relative refractive index of the base with respect to the second protective layer are equal to or greater than 0.86 and equal to or less than 1.15.

12. The conductive sheet according to claim 10, further comprising:

a first dummy electrode portion that is formed on the one main surface and is formed from a plurality of thin metal wires electrically insulated from the first conductive portion,

wherein the first conductive portion includes a plurality of first conductive patterns which are disposed in one direction and to which a plurality of first sensing portions are respectively connected,

the first dummy electrode portion includes a plurality of first dummy patterns disposed in an opening portion between the first conductive patterns adjacent to each other, and

a wiring density of the first dummy patterns is equal to a wiring density of the first conductive patterns.

13. The conductive sheet according to claim 1, wherein the conductive portion is formed on one main surface of the base.

14. A touch panel comprising:

the conductive sheet according to claim 1; and

a detection control unit that detects a contact position or a proximity position from a main surface side of the conductive sheet.

15. A display device, comprising:

the conductive sheet according to claim 1;

a detection control unit that detects a contact position or a proximity position from one main surface side of the conductive sheet; and

a display unit that displays an image on a display screen based on a display signal,

wherein the conductive sheet is disposed on the display screen with another main surface side facing the display unit.

16. A method for producing a conductive sheet, comprising:

a generation step of generating image data representing a design of a mesh pattern in which different mesh shapes are arrayed;

a calculation step of calculating an evaluation value, which quantifies a degree of variation of centroid positions of the mesh shapes, based on the generated image data;

a determination step of determining a piece of the image data as output image data based on the calculated evaluation value and predetermined evaluation conditions; and

an output step of obtaining a conductive sheet, in which the mesh pattern is formed on a base in plan view, by outputting and forming a conductive wire on the base based on the determined output image data,

wherein, in the calculation step,

a predetermined spatial frequency is set,

an average intensity on a spatial frequency band side higher than the predetermined spatial frequency and an average intensity on a spatial frequency band side lower than the predetermined spatial frequency are calculated based on the two-dimensional power spectrum of a centroid position distribution of the mesh shapes obtained based on the generated image data, and

a trail to calculate a root mean square deviation (RMS) of each centroid positions of the mesh shapes and arbitrarily selected which are disposed along a predetermined direction with respect to a direction perpendicular to the predetermined direction based on the generated image data is repeated to obtain the RMS in each trial and the average value (RMSave) thereof and the evaluation value (EV) is calculated by using the RMS and the RMSave, and

wherein, in the determining step,

a piece of the image data is determined such that,

the average intensity on the spatial frequency band side higher than the predetermined spatial frequency is larger than the average intensity on the spatial frequency band side lower than the predetermined spatial frequency, and

the evaluation value (EV) is equal to or greater than 15 μ

m and equal to or less than 65 μ

m.

18. The method according to claim 16, wherein the evaluation value (EV) is calculated by the following expression

17. A non-transitory computer-readable recording medium that records a program causing a computer to execute as a procedure:

a generation step of generating image data representing a design of a mesh pattern in which different mesh shapes are arrayed;

a calculation step of calculating an evaluation value, which quantifies a degree of variation of centroid positions of the mesh shapes, based on the generated image data; and

a determination step of determining a piece of the image data as output image data based on the calculated evaluation value and predetermined evaluation conditions,

wherein, in the calculation step,

a predetermined spatial frequency is set,

an average intensity on a spatial frequency band side higher than the predetermined spatial frequency and an average intensity on a spatial frequency band side lower than the predetermined spatial frequency are calculated based on the two-dimensional power spectrum of a centroid position distribution of the mesh shapes obtained based on the generated image data, and

a trail to calculate a root mean square deviation (RMS) of each centroid positions of the mesh shapes and arbitrarily selected which are disposed along a predetermined direction with respect to a direction perpendicular to the predetermined direction based on the generated image data is repeated to obtain the RMS in each trial and the average value (RMSave) thereof and the evaluation value (EV) is calculated by using the RMS and the RMSave, and

wherein, in the determining step,

a piece of the image data is determined such that,

the average intensity on the spatial frequency band side higher than the predetermined spatial frequency is larger than the average intensity on the spatial frequency band side lower than the predetermined spatial frequency, and

the evaluation value (EV) is equal to or greater than 15 μ

m and equal to or less than 65 μ

m.

19. The non-transitory recording medium according to claim 17, wherein the evaluation value (EV) is calculated by the following expression