JP2002109998A - Switch with at least one flexible conductive member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switch having at least one flexible conductive member. SOLUTION: The switch (10) includes a first and a second substrates (14, 20) with a conductive surface, which may be one of conductive layers (16, 22) facing each other across a groove as the case may be. The first substrate (14) is flexible and includes an intrinsically conductive substituted or non-substituted polythiofen as a conductive coating (16) as the case may be. One of the substrates is pushed toward the other to lead the two conductive surfaces to contact each other, and then the switch completes an electric circuit including wires (28, 30). Polarity applied on the surface of intrinsically conductive substitute or non-substituted polythiofen is preferably negative. Voltage applied on the electric circuit is preferably less than 5 V, and more preferably voltage applied on the electric circuit is less than 3 V, and still more preferably, voltage applied on the electric circuit is less than 1 V.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates generally to switches. More specifically, the present invention relates to switches of the type where two conductive surfaces are in contact, such as a membrane switch and a resistive touch screen.

[0002]

BACKGROUND OF THE INVENTION Switches of the type where two conductive surfaces are in contact are used in technologies such as resistive touch screens and membrane switches. For convenience and clarity reasons, this background section describes a touch screen.

[0003] Touch screens are used in computer technology to input data. Instead of a computer user using a keyboard or mouse to enter data, the user enters data through a touch screen attached to a computer monitor. US Pat. No. 4,306,110; US Pat. No. 5,438,168; US Pat. No. 5,541,370; US Pat. No. 5,589,857; US Pat. No. 5,818,43.
0; and U.S. Pat. No. 5,840,175 discloses a resistive touch screen.

[0004] The basic structure of a resistive touch screen comprises a first flexible substrate (coversheet) and a second substrate bonded to the coversheet. The first substrate typically comprises a thin layer of plastic, for example, poly (ethylene terephthalate) (PET). The first substrate has opposing first and second surfaces, the first surface facing the user of the computer, and the second surface being the surface of the second substrate. Is facing toward you. The second surface of the first substrate is conductive, for example, a conductive element (conductor).
element. The second substrate generally comprises glass, but it is also possible to use other transparent plastic materials, which are flat or curved to match the curvature of the computer monitor. The second substrate has a conductive surface, for example, coated with a conductive element facing the first substrate and also facing the user of the computer.

[0005] The conductive element is a transparent conductive coating, typically made of a thin layer of a metal or metal oxide, for example indium tin oxide (ITO), but with another metal or metal oxide. It is also possible to use. The composition and application of the ITO coating is disclosed in US Pat. No. 5,776,373,
U.S. Pat. No. 5,851,642 and U.S. Pat.
No. 042,752.

[0006] Such touch screens typically also include a plurality of spacer dots, wherein the spacer dots are provided on the upper surface (either the cover sheet (first substrate) or the second substrate). Attached to a conductive coating overlying one of the facing surfaces. Spacer dots are described in U.S. Pat. No. 5,220,136, but other spacer dots can be used. Such spacer dots separate the cover sheet (first substrate) from the second substrate. When touching the cover sheet, two conductive surfaces [one is the surface of the cover sheet (first substrate) and one is the two
The surface of the second substrate is compressed together to complete an electrical circuit, which also comprises conductive elements, such as wires, attached to the edges of the conductive surface. The particular location of the touch, and thus the contact of the conductive surface with the conductive surface, is where the contact creates and transfers data.

[0007] European Patent Application Publication No. 0 1285
No. 29 is provided with connections arranged electrically insulated from one another and additionally with a conductive bridging element, which is electrically connected to one or both of said contact elements. A pressure switch is disclosed with two contact elements, which are insulated and can also contact it or they when they are under pressure], wherein the bridging element is It is characterized by comprising a conductive pyrrole polymer.

[0008] A problem with traditional touch screens is that there is a trade-off between the mechanical properties of the flexible sheet contained in the cover sheet (first substrate) and the conductive surface of the first substrate. In a relationship. The traditional materials used in the conductive surface are generally brittle, which can crack and repeatedly bond with the flexible plastic sheet contained in the first substrate when subjected to repeated deformation. . This, in turn, disrupts the continuity of the current-carrying path at the conductive surface, and as a result, the touch screen cannot now accurately report the location of the contact.
What is needed is a conductive surface that bonds to a flexible, durable and flexible sheet over the life of the switch. If such a conductive surface is used in a touch screen, it must also be transparent.

[0009] In addition to the above mentioned disadvantages of metal and metal oxide coatings, the lifetime of ITO coatings is limited, ie they generate the required current for several touches.
ches) and no longer transmit. Also, ITO coatings are relatively expensive and have low resistance to mechanical damage. What is needed is a transparent conductive coating that has a longer life, lower cost, and is resistant to mechanical damage.

[0010]

One aspect of the present invention is a switch in which the conductive surface is inexpensive and has improved mechanical properties, ie, is not brittle and remains bonded to the flexible sheet of the first substrate even after prolonged use. Is to provide.

[0011] It is a further aspect of the present invention to provide a touch screen with an extended life.

[0012] Further aspects and advantages of the invention will become apparent from the description hereinafter.

[0013]

SUMMARY OF THE INVENTION The present invention solves the above problem by changing both the material used on the transparent conductive surface of the first substrate (coversheet) and the electrical properties of the electrical circuit.

In the present invention, a first improvement over traditional touch screen technology, an essentially conductive polymer layer is used as a coating over a flexible plastic sheet of a first substrate (coversheet). The essentially conductive polymer coating over the flexible plastic sheet is used to cover the plastic sheet of the first substrate (coversheet).
Compared with the TO coating, it is less brittle, has higher flexibility against mechanical damage, and is available at low cost. Furthermore, covering the plastic sheet with an essentially conductive polymer coating, rather than a metal coating, does not cause such coatings to crack or peel off the first substrate (coversheet) plastic sheet. Longer life.
We believe that the switch described above is not susceptible to mechanical damage after prolonged use, but that the switch has only one conductive coating, consisting essentially of a conductive polymer. Has a limited lifetime when it consists essentially of a metal or metal oxide, such as ITO. Surprisingly, an inherently conductive polymer has to be used to obtain the advantage that an essentially conductive coating has improved mechanical properties over a metal or metal oxide coating. It has been found that the excitation of an electric circuit using a touch screen incorporating a LM needs to be carefully adjusted. If a conventional metal or metal oxide coating, such as ITO, is used, the excitation of the electrical circuit need not be so carefully adjusted, and if such a conventional material is used, there is no additional advantage. I can't get it. In particular, when one seeks to maximize the benefits of the improved mechanical properties of such an essentially conductive polymer coating, the level of the excitation voltage and the voltage applied to the essentially conductive polymer coating Both polarities need to be carefully adjusted. The touch screen requires that the excitation voltage be reduced from 5 volts DC typically used in many commercially available touch screens. The same effect is observed with the AC voltage.
Additionally, maintaining the essentially conductive polymer coating under a DC voltage significantly increases the durability of the touchscreen. Such surprising effects are not observed when using ordinary metal or metal oxide coatings.

A first substrate having a conductive surface (coversheet) [the first substrate essentially comprises a conductive polymer] and a second substrate having a conductive surface [the substrate is A switch comprising: a switch positioned apart from the first substrate;
Generating a signal indicative of said contact upon contact with the conductive surface of a second substrate], wherein said switch comprises a polythiophene wherein said essentially conductive polymer is substituted or unsubstituted. It is characterized by being.

[0016] Furthermore, it is also possible to use an electric circuit comprising the switch disclosed above and a voltage source for providing a voltage difference between the conductive surface of the first substrate and the conductive surface of the second substrate. The aspects of the present invention are realized.

Also, aspects of the present invention may be realized by using an electrical appliance comprising the above disclosed switch or the above disclosed electrical circuit.

[0018] The aspects of the invention may also be realized by using a touch screen comprising the switch disclosed above or the electrical circuit disclosed above.

The aspects of the present invention can also be realized by using a switch comprising the above disclosed switch or a keyboard comprising the above disclosed electrical circuit.

Preferred embodiments of the switch and the electric circuit according to the present invention are specified in the independent claims.

[0021]

DETAILED DESCRIPTION Definitions The use of the term "coversheet" also refers to a first substrate having a flexible, conductive surface according to the present invention.

Switch The switch of the present invention comprises a first substrate and a second substrate. The first substrate (the cover sheet) of the switch comprises a flexible support (the first support) and an essentially conductive substituted or unsubstituted polythiophene and has a flexible, conductive surface. The second substrate of the switch comprises a support (second support) and has a conductive surface.

According to a first embodiment of the switch of the present invention,
The conductive surfaces of the first and second substrates are spaced apart and face each other, thus touching the first substrate and its conductive surface and the second substrate Electrical contact is achieved because the conductive surfaces can be pressed together.

According to a second embodiment of the switch of the present invention,
A first terminal extends from the conductive surface of the first substrate and a second terminal extends from the conductive surface of the second substrate, and the first substrate moves to the first terminal when the first substrate moves.
The first terminal forms an electrical circuit such that the conductive surface of the second substrate contacts the conductive surface of the second substrate to complete the circuit.

According to a third embodiment of the switch of the present invention,
An electrical circuit comprising a voltage source for providing a voltage difference between a surface layer of the first substrate and a surface layer of the second substrate;
The electrical circuit is completed by touching the first substrate, resulting in the surface layer of the first substrate and the surface layer of the second substrate being pressed together.

According to a fourth embodiment of the switch of the present invention,
The polarity of the conductive layer of the first substrate is negative compared to the conductive surface of the second substrate.

According to a fourth embodiment of the switch according to the invention, the conductive surface of said second substrate is a conventional conductive inorganic coating, such as ITO.

According to a fifth aspect of the switch of the present invention,
The switch further comprises a plurality of spacer dots located on the conductive surface of the first substrate or the conductive surface of the second substrate.

According to a sixth embodiment of the switch of the present invention,
A first substrate (coversheet) comprising a first support and a first conductive coating adhered to a first surface of the first support [this first conductive coating is essentially Comprising an electrically conductive substituted or unsubstituted thiophene], and a second support and one of the second support
A second substrate comprising a second conductive coating adhered to a second surface, the first substrate and the second substrate including the first conductive coating and the second conductive coating. The conductive coatings are positioned facing each other, and the potential applied across the first conductive coating and the second conductive coating is less than 5 volts.

In the present invention, other elements, such as tie-layers, may also be used to improve adhesion.
(Not shown) and the like may be used, and they may be located between the plastic sheet of the first substrate (cover sheet) and the conductive polymer layer.

First substrate of the present switch The first substrate (cover sheet) of the switch of the present invention is:
It comprises a flexible support (first support) and a substituted or unsubstituted polythiophene that is essentially conductive and has a flexible conductive surface. Further, the conductive surface of the first substrate may also contain an essentially conductive substituted or unsubstituted polythiophene.

The essentially conductive substituted or unsubstituted polythiophene of this first substrate can be provided by standard coating techniques or lamination. The flexible support of the first substrate (first support) used in the present invention is preferably
Plastic sheets such as poly (ethylene terephthalate), poly (ethylene naphthalate), polystyrene, polyether sulfone, polycarbonate, polyacrylate, polyamide, polyimide, cellulose triacetate, polyolefin, polyvinyl chloride, and other plastics with similar properties It is also possible to provide it with a subbing layer in some cases.

According to a preferred embodiment of the present invention, the conductive surface of the first substrate is a conductive surface of a conductive coating, ie, the first substrate comprises a support (first support) and a conductive coating. Comprising.

A soft glass / plastic laminate provided with a conductive coating, for example, WO 99/2170
7, laminates such as those described in WO 99/21708 and EP-A-0113 413 can also be used as the first substrate of the switch according to the invention.

The first substrate is preferably substantially transparent, ie has a white light transmission of at least 80%, more preferably at least 90%, most preferably at least 95%. It is characterized by.

An additional layer, for example anti-gl, is provided on the surface of the first substrate opposite the conductive coating.
are) layer or scratch resistant hard coat (har)
dcoat) layers and the like can also be provided.

Second Substrate of the Switch The second substrate of the switch of the present invention comprises a support (second support) and has a conductive surface. This 2
The support of the second substrate (the second support) need not be flexible and may be an inorganic substrate, such as ceramic or glass, but other transparent materials, such as plastic, may also be used. It is possible.

The conductive surface of the second substrate according to a preferred embodiment of the present invention is the conductive surface of a conductive coating, that is, the second substrate comprises a support (second support) and a conductive coating. Comprising.

The second substrate may be flat or curved, for example, to match the curvature of a computer monitor screen. The conductive surface of this second substrate may be indium tin oxide (ITO) or may be made of another transparent metal or metal oxide coating or essentially conductive polymer. Good.
It is also possible to provide an additional layer on the side of the second substrate opposite the conductive coating, such as an anti-gloss layer or a scratch-resistant hard coat layer.

Electrical Circuit An electrical circuit according to the present invention includes the switch disclosed above and a voltage source that provides a voltage difference between the conductive surface of the first substrate and the conductive surface of the second substrate. Become. Such an electrical circuit is shown in FIG.

The voltage source according to the first aspect of the electric circuit of the present invention is an AC voltage source.

The voltage source according to the second aspect of the electric circuit of the present invention is a DC voltage source, in which case the conductive surface of the first substrate is connected to the negative polarity of the DC voltage source.

According to a third aspect of the electric circuit of the present invention,
The voltage difference in this case is less than 5 volts.

According to a fourth embodiment of the electric circuit of the present invention,
The voltage difference in this case is less than 3 volts.

According to a fifth aspect of the electric circuit of the present invention,
The voltage difference in this case is less than 1 volt.

Touchscreen A touchscreen comprising a switch according to the invention or an electrical circuit according to the invention.

When the switch of the present invention is used as a component of a touch screen according to the first aspect of the touch screen of the present invention, the first substrate and the second substrate are substantially transparent, that is, each white light transmittance. Is at least 8
A switch characterized by 0%, more preferably at least 90%, most preferably at least 95% is preferred.

According to a second aspect of the touchscreen of the present invention, the touchscreen comprises a first substrate (coversheet) comprising a first support, the first support comprising plastic. ), A second substrate spaced apart from the first substrate, a first conductive coating covering the first support [the first conductive coating has opposing surfaces, One of the opposing surfaces of the first conductive coating faces the first support and the other of the opposing surfaces of the first conductive coating faces the second substrate. Facing, said first conductive coating comprising essentially conductive substituted or unsubstituted polythiophene], a second conductive coating covering said second support [this 2 The first conductive film is the first conductive film. Remote from the coating, the second conductive coating having a surface facing the first conductive coating and positioned away therefrom], and a plurality of spacer dots [ Spacer dots are located on a first conductive coating or a second conductive coating covering a surface of the conductive coating facing the other conductive coating, and the spacer dots are disposed on the conductive coating. A first terminal extending from the first conductive coating, a second terminal extending from the second conductive coating,
Wherein the first terminal and the first terminal are arranged such that, when the first conductive coating and the second conductive coating are pressed together, an electrical circuit for transmitting an electrical signal to a receiving medium is completed. The second conductive coating, the second conductive coating, and the second terminal form an electric circuit.

FIG. 9 shows a touch screen 10 according to the present invention.
Is shown. The first substrate (coversheet) 12 comprises a transparent polyethylene terephthalate (PET) sheet 14 and an overlying conductive coating 16 thereon. The conductive coating 16 has a conductive surface 18 that faces in a different direction from the PET sheet 14. The first substrate conductive coating 16 is essentially transparent, comprising a conductive polymer.

The touch screen 10 shown in FIG.
A second substrate 20 is also comprised. The second substrate 20 comprises a support and a conductive coating 22, which has a conductive surface 24 facing the conductive coating 16 of the first substrate, and Located away. The conductive coating of this second support is made of ITO.

The touch screen 10 further includes spacer dots 26 of a type well known to those skilled in the art.
Are also included. This plurality of spacer dots 26
Is the conductive surface 1 of the conductive coating 16 of the first substrate.
8, a conductive coating 2 of said second substrate
The spacer dot 26 faces the conductive surface 24 of the second substrate or is located away from the conductive surface 24 of the second substrate. It is also possible to face and be spaced from the conductive surface 18 of the conductive coating 16 of the substrate.

The touch screen 10 also includes a plurality of conductive elements, which are electrically connected to the conductive coatings 16 and 22 to form an electrical circuit when the conductive coatings come into contact with each other. The first conductive coating 16 is connected to a power source (not shown) located in a computer monitor (not shown) by a wire 28, and the second conductive coating 22 is also connected to a wire 30 (not shown). Connected to a receiving medium (not shown) located in a computer monitor (not shown). Numerous alternative structural arrangements for the conductive element are possible, for example, US Pat. No. 4,306,110; US Pat. No. 5,438,168; US Pat. No. 5,541,370; US Pat. 857; U.S. Patent No. 5,818,43
0; and US Pat. No. 5,840,175, each of which is incorporated herein by reference, is possible.

The essentially conductive polymer used in the present invention may be any essentially conductive polymer known in the art, for example, polyacetylene, polypyrrole. , Polyaniline, polythiophene and the like. Details regarding suitable polymers that are intrinsically conductive can be found in instructional books such as "Ad
vances in Synthetic Metal
s ", edited by P. Bernier, S. Lefrant, and G. Bidan, Elsevier, 1999;
“Intrinsically Conducting
Polymers: An Emerging Tech
nology ", Kluwer (1993);" Con.
ducting Polymer Fundamental
als and Applications, APra
physical Approach ", P. Chandr
Askhar, Kluwer, 1999; and "Ha
ndbook of OrganicConducti
ng Molecules and Polymer
s ", Walwa Editing Volume 1-4 Marcel Dek
ker Inc. (1997).

According to a seventh aspect of the switch of the present invention,
The essentially conductive substituted or unsubstituted polythiophene has the formula:

[0055]

Embedded image

Wherein n is greater than 1, preferably greater than 5, and R ₁ and R ₂ are each independently hydrogen or optionally substituted C
Represents an _1-4 alkyl group, or taken together, an optionally substituted C _1-4 alkylene group, or an optionally substituted cycloalkylene group, preferably an ethylene group, A methylene group optionally substituted with alkyl, an ethylene group optionally substituted with C _1-12 alkyl or phenyl, 1,3
-Represents a propylene group or a 1,2-cyclohexylene group]. A very suitable substituted polythiophene is poly (3,4-ethylenedioxythiophene) (PED
OT), which are described in U.S. Pat. No. 5,766,515 and EP-A-686 662, which are incorporated herein by reference.

The conductive surface layers of the first and second substrates may be formed by a known coating method, for example, spin coating, dip.
p) coating, rod coating, blade coating, air knife (a)
ir knife coating, gravure
ure) coating, reverse roll (reverser)
all) coating, extrusion coating, slide coating and curtain (cu)
It can be obtained by applying a coating solution or dispersion containing the intrinsically conductive polymer using, for example, an rtane) coating. The applied solution or dispersion can be dried and cured by a known method. An overview of such coating technology is described in "M.
oder Coating and Drying
Technology ", Edward Cohen
And Edgar B. Gutoff Editor
s, VCH Publishers, Inc., New
See York (1992). The conductive film thus obtained preferably has a surface resistance of <5.
0000 Ω / square.

The preparation of essentially conductive polythiophenes and aqueous dispersions containing said polythiophenes and polyanions is described in EP-A-440 957 and the corresponding US Pat. No. 5,300,575. . The formation of polythiophene is determined by the following formula in the presence of a high molecular weight polyanion compound:

[0059]

Embedded image

The oxidative polymerization of the 3,4-dialkoxythiophene or 3,4-alkylenedioxythiophene proceeds according to the formula wherein R ¹ and R ² are as defined above.

The thiophene corresponding to the above formula, the polyacid and the oxidizing agent are dissolved in an organic solvent or preferably in water (optionally in a certain amount of organic solvent) and the resulting solution or emulsion is then dissolved. By stirring at 0 ° C. to 100 ° C. until the polymerization reaction is completed, a stable aqueous solution or dispersion of polythiophene can be obtained. Although the polythiophenes resulting from such oxidative polymerizations are positively charged, it is not possible to accurately determine the location and number of such positive charges, and therefore, a general representation of the repeating units of a polythiophene polymer I didn't mention it in the formula.

The oxidizing agent is an oxidizing agent typically used in oxidative polymerization of pyrrole. Am. Soc. 8
5, 454 (1963). Suitable oxidizing agents that are inexpensive and easy to handle are iron (III) salts, such as FeC
l ₃ , Fe (ClO ₄ ) ₃ , and iron (III) salts of organic acids and inorganic acids containing organic residues. Other suitable oxidizing agents are _{H 2 O 2, K 2 Cr} 2 O 7, persulfate of an alkali or ammonium, perborates of the alkali, potassium permanganate and copper salts, for example, in tetrafluoroboric acid copper is there. It is also possible to use air or oxygen as the oxidizing agent. The amount of oxidizing agent required for the oxidative polymerization of thiophene is theoretically 2.25 equivalents per mole of thiophene (J. Polym. Sci. Part A, Polymer Chemistry, Vol. 26, 1
287, 1988). However, in practice, the oxidizing agent is used in excess, for example, 0.1 mol / mol thiophene.
To 2 equivalents in excess.

It is also possible for the polyacids to form polyanions or, alternatively, to add the polyanions as salts of the corresponding polyacids, for example as alkali salts. Suitable polyacids or salts thereof are high molecular weight carboxylic acids such as poly (acrylic acid), poly [(meth) acrylic acid] and poly (maleic acid), or high molecular weight sulfonic acids such as poly (styrene sulfonic acid) (P
SS) or poly (vinyl sulfonic acid). Alternatively, copolymers made from such carboxylic acids and / or sulfonic acids and other polymerizable monomers, such as styrene or acrylate, can be used. Particularly, PSS is preferable. The molecular weight of the polyacid forming such a polyanion is preferably from 1000 to 2
x10 ⁶ , more preferably in the range of 2000 to 5 × 10 ⁵ . Such polyacids or their alkali metal salts are commercially available and are known in the art, for example, Houb.
en-Weyl, Method der Orange
Nische Chemie, Bd. E20 Mark
romolekulare Stoffe, Tail
2, (1987), p. 1141.

The solution or dispersion containing the essentially conductive polymer thus obtained can be used as the base material of the coating solution or dispersion. Such coating solutions or dispersions may also contain additional materials, such as one or more binders, one or more surfactants, spacing particles, UV filters or IR absorbers. is there. Suitable high molecular weight binders are described in EP-A-564 911. Such a binder may be used as a curing agent, for example, in EP-A-5649.
It can also be treated with an epoxy silane as described in No. 11 which is particularly suitable for coating glass substrates.

The coating solution or dispersion containing such an intrinsically conductive polymer, and preferably also a linear, branched or cyclic aliphatic C _2-20 hydrocarbon, or Aromatic C optionally substituted by
_6-14 hydrocarbons, or pyran or furan [such organic compounds contain at least two hydroxy groups or a -COX or -CONYZ group, where X is-
OH and Y and Z independently of one another represent H or alkyl), or a heterocyclic compound containing at least one lactam group. Examples of such organic compounds are N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidone, N, N, N ', N'-tetramethylurea,
Formamide, dimethylformamide and N, N-dimethylacetamide. Suitable examples are sugars or sugar derivatives such as arabinose, saccharose, glucose,
Such as fructose and lactose, or di- or polyalcohols such as sorbitol, xylitol, mannitol, mannose, galactose, sorbose, gluconic acid, ethylene glycol, di- or tri (ethylene glycol), 1,1,1-trimethylolpropane 1,3-propanediol, 1,5-pentanediol, 1,2,3-propanetriol,
Examples include 1,2,4-butanetriol, 1,2,6-hexanetriol, or aromatic di- or polyalcohols such as resorcinol.

INDUSTRIAL APPLICATION The present switch and the present electric circuit can be used in all electric appliances, for example, in a keyboard including a membrane switch. The most preferred implement is a resistive touch screen.

[0067]

EXAMPLE A series of tests described hereinbelow as Experiments 1 through 6 were performed using the test fixture shown in FIG. Such an assembly is called Elo Touchsys
tems, Inc. Standard 2 incorporating an AccuTouch ™ touch screen, commercially available from (Fremont, CA).
This was accomplished by retrofitting a 6.4 cm (10.4 inch) display. This standard AccuTouch ™ touch screen construction comprises a cover sheet (first substrate) comprising a PET plastic sheet 32 covered with a transparent conductive coating 16 made of ITO.
And also comprising a glass support 33 covered with a transparent conductive coating 22 made of ITO. The two transparent conductive coating surfaces face each other and are spaced apart. Spacer dots are placed over the coversheet (first substrate) coating, facing the conductive coating of the glass screen but not touching it.

In this experiment, the replacement of the ITO of the transparent conductive coating of the cover sheet (first substrate) with a coating consisting essentially of a conductive polymer was performed, through the standard described above. The structural arrangement was modified. The particular intrinsically conductive polymer used was PEDOT / PSS, which is available from Agfa-Gevaert N.A. V. (M
ortsel, Belgium) under the trademark ORGACON ^™ E
It is commercially available as a coating over a 175 micrometer thick polyethylene terephthalate film under L3TG.

A pneumatic piston is mounted on the surface opposite the conductive surface so as to rest on the first substrate and a 340 g (12 ounce) load is applied to the needle at 3 per second.
Called at a frequency of times. The needle 31 is made of hard plastic, specifically, General Electric Comp.
CYCOLAC ™ commercially available from any
It was made of T4500 ABS. The radius of the tip of the needle was 0.76 mm (0.030 inch). The tip was carefully positioned so that it hit the center of the area defined by four of the plurality of spacer dots present on the surface of the first substrate opposite the conductive surface. When the tip of the needle hits the first substrate, the conductive film covering the first substrate and the conductive film covering the second substrate of the touch screen are pressed and contacted. The electric circuit is completed. As shown in FIG. 10, a 1000 ohm resistor R1 and a 9000 ohm resistor R2 were connected in series with the first substrate conductive coating. A data acquisition device was used to continuously monitor the voltage drop V across this resistor R1. This circuit also includes a pair of input terminals A and B.

Experiment 1 In this experiment, 5 volts D were applied across input terminals A and B.
Voltage potential of C (voltage potential)
This is the voltage commonly used in the touch screen industry. The voltage at terminal A was made positive with respect to terminal B as taught in US Pat. No. 5,766,515. As the electrical contact created by the contact between the conductive surface of the first substrate and the conductive surface of the second substrate deteriorates, the amount of current flowing during each contact decreases, thereby causing a voltage drop across the series resistance. The degree of is low.

If the electrical contact deteriorates to the extent that an appropriate electrical circuit is not completed when the conductive surfaces are brought into contact,
Touch screen failures can occur. A decrease in the amount of current by 50 percent, as indicated by a 50 percent drop in voltage across resistor R1, is a reasonable indication that the touch screen has failed. FIG. 1 shows that the measured voltage V across the resistor R1 is about 1
It is shown that it is reduced by 50% after 400 touches T.

Experiment 2 In Experiment 2, 5 volts D
A voltage potential of C was applied, however, in experiment 2, the polarity was reversed compared to experiment 1, ie, terminal A had a negative voltage with respect to terminal B. FIG. 2 shows a resistor R1
Is not reduced to 50% even after about 80,000 touches T, which corresponds to a 57-fold improvement over Experiment 1.

Experiment 3 In Experiment 3, terminal A was again given a positive polarity, but the voltage potential across input terminals A and B was lowered from 5 volts DC to 0.5 volts DC. FIG. 3 shows that the drop in voltage V across resistor R1 is negligible even after about 130,000 touches T. This experiment was continued until the touch T became approximately 1.81 million touches in total. FIG. 4 shows that the voltage drop over the last 120,000 touches T of this test is only a few percent lower than the original voltage V shown in FIG. 50 of the measured voltage V across the resistor R1 throughout the experiment lasting over 1.81 million touches T
No percent reduction occurred.

Experiment 4 In Experiment 4, the terminal A was given a negative polarity again (similar to Experiment 2), but the voltage potential across the input terminals A and B was lowered from 5 volts DC to 0.5 volts DC. did. FIGS. 5 and 6 show that there was no 50 percent drop in measured voltage V across resistor R1 over the entire experiment lasting over 1.3 million touches T.

It has been found from the above experiments that the number of touches before the device malfunctions greatly increases even if the polarity is reversed or the DC voltage is reduced. This was surprising and unexpected.

Experiment 5 In Experiment 5, a 5 volt AC source operating at 60 Hz was connected to input terminals A and B. FIG. 7 shows that the measured voltage V across the resistor R1 drops by more than 50 percent after about 700 touches T.

Experiment 6 In Experiment 6, the level of the AC voltage was reduced from 5 volts to 0.5 volts. FIG. 8 shows 30,000 touches T
Shows that there was no 50 percent drop in the measured voltage V across resistor R1 throughout the experiment that continued beyond.

From the above experiment, it was found that even when the AC voltage was lowered, the number of touches T before the device failed was greatly increased. Such a result was surprising and unexpected.

As will be appreciated by those of ordinary skill in the art, the present invention is open to many variations, including, but not limited to, resistive variations. All variants of touch screens and membrane switches are included. All such variations to the invention fall within the scope of the invention.

[Brief description of the drawings]

FIG. 1 shows the voltage V across a resistor R1 of Experiment 1 performed using the test apparatus of FIG. 10 with a circuit voltage of 5V and a cover sheet (first substrate) with positive polarity.
Is a chart showing a function of the number of touches T.

FIG. 2 shows the voltage V across the resistor R1 of Experiment 2 performed with the test apparatus of FIG. 10 at a circuit voltage of 5V and a cover sheet (first substrate) having a negative polarity.
Is a chart showing a function of the number of touches T.

FIG. 3 shows the voltage across resistor R1 of experiment 3 performed using the test apparatus of FIG. 10 with a circuit voltage of 0.5V and a cover sheet (first substrate) with positive polarity. 5 is a chart showing V as a function of the number of touches T.

FIG. 4 shows the voltage across resistor R1 of experiment 3 performed using the test apparatus of FIG. 10 with a circuit voltage of 0.5V and a positive cover sheet (first substrate). 5 is a chart showing V as a function of the number of touches T.

FIG. 5 shows the voltage across resistor R1 of experiment 4 performed using the test apparatus of FIG. 10 with a circuit voltage of 0.5 V and a cover sheet (first substrate) with a negative polarity. 5 is a chart showing V as a function of the number of touches T.

FIG. 6 shows the voltage across resistor R1 of experiment 4 performed using the test apparatus of FIG. 10 with a circuit voltage of 0.5V and a cover sheet (first substrate) with a negative polarity. 5 is a chart showing V as a function of the number of touches T.

FIG. 7 is a chart showing the voltage V across the resistor R1 as a function of the number of touches T in Experiment 5 performed with the test fixture of FIG. 10 at a circuit AC voltage of 5 V and 60 Hz.

FIG. 8 is a chart showing the voltage V across the resistor R1 as a function of the number of touches T in Experiment 6 performed with the test fixture of FIG. 10 at a circuit AC voltage of 0.5 V and 60 Hz. .

FIG. 9 is a schematic view of a touch screen according to the present invention.

FIG. 10 is an illustration of a circuit device used in accordance with the present invention.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Lawrence M. Welshille 94070 San Carlos Elm Street, Calif., United States 1124 (72) Inventor Leonard H. Radzirowski 94043, California, U.S.A. Field Road 777 (72) Inventor Tom Kroats Belgian Bee 2640 Malt Cell Septes Trat 27 Agfa-Gevert Na Mrose Fennoutjaps (72) Inventor Babo Muis Belgium Bee 2640 Malt Cell Septes Trat 27・ Agfa-Gevaert-Nar Mrose Fennoutjap (72) Inventor Peter Wei Ruto Belgium Be 2640 Morutoseru-Seputesu Trat 27 - Agfa - Gevaert toner Muroze and non-end notebook Shea guy-flops in the F-term (reference) 5G006 AA01 AZ08 BA02 BB07 FB14 FB31 5G046 AA07 AB02 AC33 AD02 AE11

Claims (6)

[Claims] 1. A first substrate (coversheet) comprising an essentially conductive polymer and having a conductive surface, and a conductive substrate located away from said first substrate and having a conductive surface. A second substrate comprising: a switch for generating a signal indicative of said contact when said cover sheet moves and contacts a conductive surface of said second substrate, said switch comprising said second substrate; The switch, wherein the hydrophilic polymer is a substituted or unsubstituted polythiophene. 2. The method according to claim 1, wherein the substituted or unsubstituted polythiophene has the following formula: Wherein n is greater than ₁ and R ₁ and R
₂ each independently represents hydrogen or an optionally substituted C _1-4 alkyl group, or together form an optionally substituted C _1-4 alkyl group Or an optionally substituted cycloalkylene group, preferably an ethylene group, optionally a methylene group optionally substituted with alkyl, optionally C _1-12
Represents an ethylene group, a 1,3-propylene group, or a 1,2-cyclohexylene group which may be substituted by alkyl or phenyl]. 3. An electrical circuit comprising a switch according to any of the preceding claims and a voltage source for providing a voltage difference between the conductive surface of the first substrate and the conductive surface of the second substrate. Electrical circuit consisting of: 4. An electric appliance comprising the switch according to claim 1 or 2 or the electric circuit according to claim 3. 5. A touch screen, comprising: the switch according to claim 1 or 2 or the electric circuit according to claim 3. 6. A keyboard, according to claim 1, wherein:
A keyboard comprising the switch according to claim 3 or the electrical circuit according to claim 3.