Input device and method for producing input device

• US 10,126,185 B2
• Filed: 10/17/2014
• Issued: 11/13/2018
• Est. Priority Date: 12/27/2013
• Status: Active Grant

• Current Assignee: Fujikura Limited
• Original Assignee: Fujikura Limited
• Inventors: Watanabe, Toshiaki, Takamatsu, Makoto, Aoki, Osamu, Tachikawa, Yasuyuki
• Primary Examiner(s): Fitzgerald, John
• Assistant Examiner(s): Mercado, Alexander
• Application Number:
  US15/108,189
• Publication Number:
  US 20160327440A1
• Time in Patent Office: 1,488 Days
• CPC Class Codes: G01L 1/20 by measuring variations in ohmic resistance of solid materials or of electrically-conductive fluids of piezo-resistive materials G01L1/18; by making use of electrokinetic cells, i.e. liquid-containing cells wherein an electrical potential is produced or varied upon the application of stress
• CPC Class Codes: G01L 1/205 using distributed sensing elements
• CPC Class Codes: G01L 27/005 Apparatus for calibrating pressure sensors
• CPC Class Codes: G06F 2203/04103 Manufacturing, i.e. details related to manufacturing processes specially suited for touch sensitive devices
• CPC Class Codes: G06F 2203/04105 Pressure sensors for measuring the pressure or force exerted on the touch surface without providing the touch position
• CPC Class Codes: G06F 2203/04106 Multi-sensing digitiser, i.e. digitiser using at least two different sensing technologies simultaneously or alternatively, e.g. for detecting pen and finger, for saving power or for improving position detection
• CPC Class Codes: G06F 3/04142 the force sensing means being located peripherally, e.g. disposed at the corners or at the side of a touch sensing plate
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact

Abstract

An input device 1 comprises a sensor circuit 91 which includes a pressure-sensitive sensor 50 and a first fixed resistor 914 which is electrically connected in series to the pressure-sensitive sensor 50. A resistance value R_f of the first fixed resistor 914 satisfies the following expression (1). In the expression (1), R_sHL is a resistance value of the pressure-sensitive sensor 50 when ½ of the maximum working load of the pressure-sensitive sensor 50 is applied, and Co is a resistance correction coefficient within the range of 1/16 to 1/1.
R_f=R_sHL×Co  (1)

Claims

1. A method for producing an input device which includes at least one sensor circuit including a first circuit and a second circuit, the first circuit including a pressure-sensitive sensor whose resistance value continuously changes in accordance with a magnitude of a pressing force, and the second circuit including a fixed resistor and being electrically connected to the pressure-sensitive sensor, the method comprising:

(a) preparing the pressure-sensitive sensor;

(b) measuring a combined resistance value R_sHL of the first circuit when ½

of a maximum working load of the pressure-sensitive sensor is applied;

(c) selecting a resistance correction coefficient Co from a range of 1/16 to 1/1; and

(d) making the sensor circuit by preparing the second circuit which has a combined resistance value R_f of a following expression;

R_f =R_sHL ×

CO.

2. The method for producing the input device according to claim 1, wherein the maximum working load is 8 [N].

3. The method for producing the input device according to claim 1, wherein

the maximum working load is a load at a point when the combined resistance value of the first circuit decreases by 50 [Ω

] while a load applied to the pressure-sensitive sensor increases by 1 [N].

4. The method for producing an input device according to claim 1, wherein

the (c) includes selecting the resistance correction coefficient Co from a range of 1/8 to 1/2.

5. The method for producing the input device according to claim 1, wherein

the input device includes a plurality of sensor circuits each of which is the sensor circuit. and

resistance correction coefficients Co of the sensor circuits selected in the (c) are the same.

6. The method for producing the input device according to claim 1, wherein

the input device includes:

a panel unit which includes at least a touch panel; and

a plurality of sensor circuits each of which is the sensor circuit;

each of the pressure-sensitive sensors detects a load applied through the panel unit, and

as a distance from a center of the panel unit to the pressure-sensitive sensor is shorter in a plan view, the resistance correction coefficient Co of the sensor circuit selected in the (c) is smaller.

7. The method for producing the input device according to claim 1, wherein

the pressure-sensitive sensor includes:

a spacer with an opening;

first and second substrates which face each other through the spacer;

a first electrode which is arranged on the first substrate at a position where the first electrode corresponds to the opening; and

a second electrode which is arranged on the second substrate at a position where the second electrode corresponds to the opening and faced to the first electrode.