CN102880367B - Method for calculating parameter tau of projection capacitive touch screen and graphic controller of projection capacitive touch screen - Google Patents

Abstract

The invention provides a method for calculating a parameter tau of a projection capacitive touch screen. The method comprises the following steps of: respectively calculating a resistance value and a capacitance value of each electrode, multiplying the calculated resistance value of each electrode by the calculated capacitance value of each electrode, and thus obtaining the parameter tau, wherein the resistance value of each electrode is calculated by logical partition and integration of an indium tin oxide (ITO) rhombic graph, and the capacitance value of each electrode is calculated by an equivalent capacitance model which equalizes the capacitance to a series of parallel related capacitance, so the parameter tau is simulated. Moreover, the invention also provides a corresponding graphic controller. By adoption of the method and the graphic controller provided by the invention, the parameter tau can be accurately calculated, and a sample is not required to be pre-manufactured, so the problems of high development time consumption and high cost of the projection capacitive touch screen caused by calculation of the parameter tau are solved.

Description

The parameter τ computing method of projected capacitive touch screen and graphics controller thereof

Technical field

The present invention relates to touch screen technology field, particularly relate to a kind of parameter τ computing method and graphics controller thereof of projected capacitive touch screen.

Background technology

Capacitive touch screen has been widely used in department of computer science and has unified the display device of the mobile terminals such as mobile phone.Especially along with the appearance of iphone, projected capacitive touch screen supports the features such as the good human-computer interaction interface of multiple point touching, low-power consumption and high life with it, and is extensively esthetically acceptable to the consumers.

The principle that realizes of projected capacitive touch screen is generally etch two-layer indium tin oxide (ITO) coating on the glass substrate, and form multiple ITO pattern of pressing line direction and column direction arrangement, each ITO pattern corresponds to an induction electrode.One deck ITO forms the induction electrode array of line direction (being defined as Y-direction below), and wherein a line ITO pattern forms a horizontal induction electrode array (being defined as a Y electrode below); Another layer of ITO forms the induction electrode array of column direction (being defined as X-direction below), and wherein a row ITO pattern forms a vertical induction electrode array (being defined as an X electrode below).In addition, also can only utilize one deck ITO to form each strip electrode on line direction and column direction.All induction electrodes all by a capacitive induction chip drives, to detect the capacitance variations on each induction electrode.Graphics controller calculates touch point accurate coordinates in the x-direction and the z-direction according to the capacitance change detected.The shape of ITO pattern presents irregular shape more, generally uses rhombus as shown in Figure 1 at present.

But also there are a lot of technological difficulties needing to solve in the design aspect of projected capacitive touch screen.

Such as, the simulation and emulation of the parameter τ of the most critical of projected capacitive touch screen design is exactly technological difficulties.Parameter τ refers to the time constant of every strip electrode, and it is the resistance value R of every strip electrode and the product of capacitance C:

τ=RC (1)

Therefore, parameter τ depends on resistance value R and the capacitance C of every strip electrode, and resistance value R and capacitance C depends on the structure etc. of ITO pattern.Therefore, calculating and the design of the parameter τ performance that directly has influence on projected capacitive touch screen is good and bad.

About the calculating of parameter τ, the method generally adopted at present needs to make print in advance, by measuring resistance value R and the capacitance C of every strip electrode, then calculates the parameter τ of every strip electrode according to the resistance value R measured and capacitance C.Then, then according to the parameter τ calculated determine ITO pattern structure.This method not only extends the construction cycle of project, too increases design cost simultaneously, has more crucially brought the fabrication error making print in advance into, has made the value of the parameter τ of calculating accurate not.

Summary of the invention

In order to overcome the above problems, the invention provides and a kind ofly be suitable for parameter τ computing method that ITO pattern is the projected capacitive touch screen of rhombus and graphics controller thereof.

In order to realize above object, the parameter τ computing method of projected capacitive touch screen provided by the invention comprise (ITO pattern of described projected capacitive touch screen is rhombus):

Calculate the resistance value of every strip electrode;

Calculate the capacitance of every strip electrode; With

Parameter τ is obtained by the resistance value of the every strip electrode calculated being multiplied with capacitance,

Wherein, the step of the resistance value of the every strip electrode of described calculating comprises:

The figure of every strip electrode is divided into multiple regular figure successively, and determines the equivalent resistance model of described electrode according to the position relationship of split regular figure;

Calculate the equivalent resistance of each regular figure; With

The resistance value of described electrode is calculated according to described equivalent resistance model,

Further, the step of the capacitance of the every strip electrode of described calculating comprises:

It is the capacitor equivalent model of a series of relevant capacitor parallel connection by the capacitor equivalent of every strip electrode;

For each electric capacity in described capacitor equivalent model, the model of plane-parallel capacitor is adopted to calculate its equivalent capacitance value; With

The capacitance of described electrode is calculated according to described capacitor equivalent model.

Preferably, the regular figure of described segmentation comprises the non-rectangle figure of the rectangular graph Sum fanction of rule,

The step of the equivalent resistance of each regular figure of described calculating comprises:

For the rectangular graph of rule, the square resistance of the material used by this rectangular graph calculates its resistance value,

For the non-rectangle figure of rule, perform following steps:

Described non-rectangle figure is divided into the regular figure calculating its resistance value by integration method further, and determines the equivalent resistance model of described non-rectangle figure according to the position relationship of the regular figure of segmentation further;

The equivalent resistance of each regular figure of segmentation is further calculated according to described integration method; With

The equivalent resistance of described non-rectangle figure is calculated according to described equivalent resistance model.

Preferably, the described regular figure calculating its resistance value by integration method comprises right-angled trapezium and rectangle.

Preferably, the step of the resistance value of the every strip electrode of described calculating comprises:

The figure of every strip electrode is divided into successively the non-rectangle figure of the rectangular graph Sum fanction of multiple rules of series connection, and determines the resistance in series equivalent model of described electrode according to the position relationship of split figure;

Each rectangular graph of series connection and the equivalent resistance of non-rectangle figure is calculated respectively according to the step of the equivalent resistance of each regular figure of described calculating; With

The resistance value of described electrode is calculated according to described resistance in series equivalent model;

Preferably, the capacitor equivalent model of described every strip electrode comprises: the electric capacity that rhombus and periphery 4 rhombuses are formed; Electric capacity between rhombus and TFT-LCD the superiors ITO; Figure bridging position electric capacity; Electric capacity between edge lead-in wire and adjacent legs; Electric capacity between lead-in wire and the TFT-LCD the superiors go between.

The present invention provides a kind of graphics controller of projected capacitive touch screen simultaneously, and the ITO pattern of described projected capacitive touch screen is rhombus, comprises parameter τ computing module, and described parameter τ computing module comprises:

Resistance value computing unit, it calculates the resistance value of every strip electrode;

Capacitance computing unit, it calculates the capacitance of every strip electrode; With

Parameter τ computing unit, it obtains parameter τ by the resistance value of the every strip electrode calculated being multiplied with capacitance,

Wherein, the step of the resistance value of the every strip electrode of described calculating comprises:

The figure of every strip electrode is divided into multiple regular figure successively, and determines the equivalent resistance model of described electrode according to the position relationship of split regular figure;

Calculate the equivalent resistance of each regular figure; With

The resistance value of described electrode is calculated according to described equivalent resistance model,

Further, the step of the capacitance of the every strip electrode of described calculating comprises:

It is the capacitor equivalent model of a series of relevant capacitor parallel connection by the capacitor equivalent of every strip electrode;

For each electric capacity in described capacitor equivalent model, the model of plane-parallel capacitor is adopted to calculate its equivalent capacitance value; With

The capacitance of described electrode is calculated according to described capacitor equivalent model.

Preferably, the regular figure of described segmentation comprises the non-rectangle figure of the rectangular graph Sum fanction of rule,

The step of the equivalent resistance of each regular figure of described calculating comprises:

For the rectangular graph of rule, the square resistance of the material used by this rectangular graph calculates its resistance value,

For the non-rectangle figure of rule, perform following steps:

Described non-rectangle figure is divided into the regular figure calculating its resistance value by integration method further, and determines the equivalent resistance model of described non-rectangle figure according to the position relationship of the regular figure of segmentation further;

The equivalent resistance of each regular figure of segmentation is further calculated according to described integration method; With

The equivalent resistance of described non-rectangle figure is calculated according to described equivalent resistance model.

Preferably, the capacitor equivalent model of described every strip electrode comprises: the electric capacity that rhombus and periphery 4 rhombuses are formed; Electric capacity between rhombus and TFT-LCD the superiors ITO; Figure bridging position electric capacity; Electric capacity between edge lead-in wire and adjacent legs; Electric capacity between lead-in wire and the TFT-LCD the superiors go between.

Preferably, comprise further:

Parameters revision module, it carrys out the design parameter of projected capacitive touch screen involved in corrected parameter τ computation process for the parameter τ calculated according to parameter τ computing module.

Preferably, described design parameter comprises the parameter that the structural parameters of the ITO pattern of described capacitive touch screen, the manufacturing process ability parameter of production equipment and described capacitive touch screen and TFT-LCD arrange in pairs or groups.

Parameter τ computing method provided by the present invention and graphics controller can calculating parameter τ more accurately, and without the need to making print in advance, thus solve and to cause due to the calculating of parameter τ projected capacitive touch screen to develop length consuming time, problem that cost is high.

Accompanying drawing explanation

Fig. 1 is the schematic diagram of the projected capacitive touch screen with rhombus ITO pattern;

Fig. 2 is floor map and the sectional view of projected capacitive touch screen;

Fig. 3 is the metal bridge of projected capacitive touch screen and the connection diagram of lozenge diagram;

Fig. 4 is the connection diagram of the edge lead-in wire of projected capacitive touch screen;

Fig. 5 is the schematic diagram that the mathematical model of a line lozenge diagram in projected capacitive touch screen divides;

Fig. 6 a-6d is the mathematical model of the further segmentation of each partition graph shown in Fig. 5 respectively;

Fig. 7 is the equivalent resistance model of each partition graph in Fig. 6 a-6d;

Fig. 8 is the integral model of right-angled trapezium;

Fig. 9 is the mathematical model of touch-screen edge lead-in wire;

Figure 10 is the capacitor model of rhombus and periphery rhombus;

Figure 11 is the structural representation between ITO pattern inductive layer and LCD the superiors ITO;

Figure 12 is equivalent model when calculating rhombus electric capacity;

Figure 13 is the capacitive environment of every bar edge lead-in wire.

Embodiment

The invention provides and be a kind ofly suitable for parameter τ computing method that ITO pattern is the projected capacitive touch screen of rhombus and graphics controller.This point it is emphasized that parameter τ computing method provided by the present invention and graphics controller can be applicable to all projected capacitive touch screens with rhombus ITO pattern.Below, describe the present invention with embodiment with reference to the accompanying drawings.

First, for fully understanding the present invention, be that the structure of the projected capacitive touch screen of rhombus is described to ITO pattern.Here, mainly with only with one deck ITO realize projection-type induction capacitive touch screen be exemplarily described.Specifically, one deck ITO forms multiple rhombus ITO pattern of press line direction and column direction and arranging, in the row direction by ITO by each graphical interconnections, in a column direction by metal bridge by each graphical interconnections.Certainly, also can in a column direction by ITO by each graphical interconnections, in the row direction by metal bridge by each graphical interconnections.

Fig. 2 is the floor map of projected capacitive touch screen and the sectional view along line A-A intercepting.As shown in Figure 2, projected capacitive touch screen comprises:

Glass substrate 201;

ITO responds to graph layer, and it is formed on glass substrate 201, comprising:

ITO layer 202, it comprises multiple rhombus ITO pattern by line direction and column direction arrangement and the ITO interconnecting parts that arranges in column direction, and adjacent ITO pattern that the adjacent ITO pattern of described ITO interconnecting parts on connecting column direction and connecting column direction go between with touch-screen edge and described edge go between;

Metal bridge 204, it is formed in above ITO layer 202, and by line direction arrangement, adjacent ITO pattern that the adjacent ITO pattern on connected row direction and connected row direction go between with touch-screen edge and described edge go between;

Insulation course 203, it is formed between ITO layer 202 and the metal wire (i.e. metal bridge 204) of putting up a bridge, and splits for doing the ITO pattern of row and column.

Here point out, as mentioned above, metal bridge 204 also can arrange in column direction, and contiguous ITO pattern that the adjacent pattern on connecting column direction and connecting column direction go between with touch-screen edge and described edge go between.In this case, the ITO interconnecting parts of ITO layer 202 then presses line direction arrangement, and the ITO pattern of being close to that the adjacent ITO pattern on connected row direction and connected row direction go betweens with touch-screen edge and described edge go between.

Metal bridge 204 and ITO pattern below it can adopt the mode of punching to be connected, as shown in Figure 3.In figure 3, show the metal bridge arranged in column direction, wherein, d4 represents the bridge width of metal bridge, and 2a represents the bridge joint length of metal bridge.

The metal lead wire at the edge of touch-screen as shown in Figure 4.

In an embodiment of projected capacitive touch screen, metal bridge can go between with edge and adopt identical metal material, can ensure like this edge lead-in wire and the metal lead wire of metal bridge can together with mask(photomask technique) in complete, the making of whole touch-screen completes (making of common projected capacitive touch screen needs 4-5mask altogether) by 3mask, thus saving manufacture craft, save production cost.Such as, the material of metal bridge and edge lead-in wire is chosen as metal molybdenum.Certainly, the material of metal bridge is not limited to metal molybdenum, also can use other metal material instead.

Below, parameter τ computing method provided by the present invention are described in detail.

Generally, parameter τ computing method provided by the present invention are, calculate resistance value and the capacitance of every strip electrode according to the equivalent resistance model of every strip electrode and capacitor model, then calculate parameter τ according to formula (1), thus realize the analog simulation to parameter τ.Wherein, when calculating the resistance value of every strip electrode, by the mode of mathematics logical division being carried out to ITO lozenge diagram and integration calculates, when calculating the capacitance of every strip electrode, being calculated by the equivalent capacity model being equivalent to a series of relevant capacitor parallel connection.Like this, just can know that each layer needs to plate how thick film when producing at the beginning of design in advance, overcoming existing method needs to make print in advance and the exploitation length consuming time caused, deficiency that cost is high.

Principle of the present invention is: after the thickness of the metal film of the ito film and formation metal bridge 204 that form ITO layer 202 is determined, the square resistance R ' of ito film and metal film just can determine; After the insulating material forming insulation course 203 is determined, the DIELECTRIC CONSTANT ε of insulating material just can be determined; According to formula (1), as long as after the resistance value R determining every strip electrode and capacitance C, the τ parameter needed can be obtained, to verify whether the parameter (comprising the thickness, trace width etc. of ito film, metal film, insulation course) of design meets design requirement, and designs with guide product.

Specifically, the present invention is when calculating the resistance value of every strip electrode, first, the figure of every strip electrode is divided into multiple regular figure successively, and the equivalent resistance model of this electrode is determined according to the position relationship of split regular figure, then, calculate the equivalent resistance of each regular figure, finally, the resistance value of this electrode is calculated according to equivalent resistance model.

Wherein, the regular figure of described segmentation can comprise the non-rectangle figure (such as, trapezoidal, rhombus) of the rectangular graph Sum fanction of rule.

For the rectangular graph of rule, calculate its equivalent resistance by following formula:

$R_l=R^{\′}\frac{l}{w}---\left(2\right)$

Wherein, R ' is square resistance, and l is the length that electric current flows through direction, and w is the vertical width that electric current flows through direction.

For the non-rectangle figure of rule, after adopting first segmentation, the mode of integration calculates its resistance value.Specifically, each non-rectangle figure is divided into the regular figure calculating its equivalent resistance by integration method further, such as trapezoidal and rectangle, and the equivalent resistance model determining this non-rectangle figure according to the position relationship of the regular figure of segmentation further.Then, calculate the equivalent resistance of each regular figure of segmentation further according to integration method, finally, calculate the equivalent resistance of this non-rectangle figure according to this equivalent resistance model.

Here point out, above figure segmentation is only exemplary, figure segmentation of the present invention is not limited to the figure of every strip electrode to be divided into rectangle and non-rectangle, but the figure of every strip electrode can be divided into any figure calculating its resistance value by certain mathematical way, such as triangle, trapezoidal etc.

When calculating the resistance value of every strip electrode, preferably, first, the figure of every strip electrode is divided into successively the non-rectangle figure of the rectangular graph Sum fanction of multiple rules of series connection, and the resistance in series equivalent model of this electrode is determined according to the position relationship of split figure, then, each rectangular graph of series connection and the equivalent resistance of non-rectangle figure is calculated respectively according to the step of the equivalent resistance of each regular figure of aforementioned calculating, finally, the resistance value of this electrode is calculated according to this resistance in series equivalent model.This account form can further improve counting yield.

The present invention is when calculating the capacitance of every strip electrode, first be the capacitor equivalent model of a series of relevant capacitor parallel connection by the capacitor equivalent of every strip electrode, then, for each electric capacity in this capacitor equivalent model, the model of plane-parallel capacitor is adopted to calculate its equivalent capacitance value, finally, the capacitance of this electrode is calculated according to this capacitor equivalent model.Wherein, the computing formula of the capacitance of each electric capacity in capacitor equivalent model is:

$C={\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_r\frac{s}{d}---\left(3\right)$

Wherein, ε ₀for the absolute dielectric constant of vacuum, ε _rfor the relative dielectric constant of material, s is the area of plane-parallel capacitor, and d is the distance between two parallel-plates.

Below, will the computing method of parameter τ provided by the present invention be described in conjunction with the embodiments.

(1) calculating of the resistance value of every strip electrode

First, the calculating of the resistance value of every bar Y electrode is described in detail.

Fig. 5 is the schematic diagram that the mathematical model of a line lozenge diagram in projected capacitive touch screen divides.As shown in Figure 5, a line lozenge diagram is split into the figure of 4 types, is respectively illustrated 501,502,503 and 504.

Fig. 6 a-6d is the mathematical model 601,602,603 and 604 of the further segmentation of the partition graph 501,502,503 and 504 shown in Fig. 5 respectively.From Fig. 6 a-6d, partition graph 501 is divided into two right-angled trapezium (S further ₁); Partition graph 502 rectangles as rule, therefore need not split again, and wherein 1 ₁represent that this rectangle flows through the length on direction at electric current; Partition graph 503 is divided into four right-angled trapezium (S further ₁, S ₂, S ₃, S ₄) and a rectangle (S ₅), wherein d is that this rhombus is long perpendicular to the minor face of direction of current; Partition graph 504 rectangles as rule, therefore need not split again, and wherein e is that this rectangular vertical is long in the minor face of direction of current.

Fig. 7 is the equivalent resistance model of each partition graph in Fig. 6 a-6d.In the figure 7,701 is equivalent resistance models of partition graph 601, and 702 is equivalent resistance models of partition graph 602, and 703 is equivalent resistance models of partition graph 603, and 704 is equivalent resistance models of partition graph 604.

After by the segmentation of Fig. 6 and the equivalent resistance model of Fig. 7, the calculating of the resistance on whole a line figure becomes simply clear.The resistance of the rectangular graph after segmentation can complete calculating by formula (2), and for trapezoidal portions, complete calculating by the mode of integration, the model of integration refers to Fig. 8.

In the integral model of Fig. 8, right-angled trapezium is first done boost line by the first step, supplements into a right-angle triangle, the broken line triangle part of supplementary part show look.In figure after having supplemented, if leg-of-mutton height is h, trapezoidal upper bottom side length is a, and the trapezoidal length of side of going to the bottom is c, and height is b.

If the drift angle of broken line triangle is α, the tangent value calculating drift angle can obtain following formula:

$\mathrm{tg}\left(\mathrm{\α}\right)=\frac{c}{h}=\frac{a}{h-b}=\frac{x}{h-y}---\left(4\right)$

Can calculate according to relation formula (4) Suo Shi:

$h=\frac{\mathrm{bc}}{c-a}---\left(5\right)$

$x=c-\frac{\mathrm{cy}}{h}---\left(6\right)$

Do the segmentation of several deciles at the overall height b of short transverse to right-angled trapezium of right-angled trapezium, the length that the electric current of the resistance of each decile flows through direction is dy, and wide is x.Under this model, it is dy, the wide resistant series for x that whole isosceles trapezoid is equivalent to several long, obtains trapezoidal short transverse integration:

$\mathrm{Rt}=\underset{0}{\overset{b}{\∫}}\frac{R^{\′}\mathrm{dy}}{x}---\left(7\right)$

Formula (6) is substituted into formula (7) can obtain:

$\mathrm{Rt}=\underset{0}{\overset{b}{\∫}}\frac{R^{\′}\mathrm{dy}}{c-\frac{c}{h}y}---\left(8\right)$

Formula (8) quadrature is obtained:

$\mathrm{Rt}=-\frac{h}{c}{R}^{\′}\ln (y-h){|}_0^b---\left(9\right)$

Further computing formula (9) obtains:

$\mathrm{Rt}=\frac{h}{c}{R}^{\′}\ln \left(\frac{h}{h-b}\right)---\left(10\right)$

Like this, the equivalent resistance of partition graph 601 is in two trapezoidal parallel connections, and its resistance is:

$R_{601}=\frac{\mathrm{Rt}}{2}=\frac{h}{2c}{R}^{\′}\ln \left(\frac{h}{h-b}\right)---\left(11\right)$

Partition graph 602 is the rectangular graph of a rule, and its resistance is:

$R_{602}=R^{\′}\frac{l}{w}=R^{\′}\frac{l_1}{2a}---\left(12\right)$

Wherein, w is 2 times (that is, w=2a) of right-angled trapezium upper base edge lengths, is highly l ₁.

The resistance of partition graph 603 is that two right-angled trapezium are in parallel, then connects with a rectangular resistance, more in parallel with two right-angled trapezium, and corresponding relation is: S in Fig. 6 c ₁r in corresponding diagram 7 ₄, S ₂corresponding R ₇, S ₃corresponding R ₅, S ₄corresponding R ₈, S ₅corresponding R ₆, so the resistance value of a complete rhombus 603 is:

R _d=R ₄//R ₅+R ₆+R ₇//R ₈(13)

Wherein, R ₄//R ₅and R ₇//R ₈equal R ₆₀₁, therefore, formula (11) and (2) are substituted into formula (13) and obtain:

$R_d=\frac{h}{2c}{R}^{\′}\ln \left(\frac{h}{h-b}\right)+R^{\′}\frac{d}{2c}+\frac{h}{2c}{R}^{\′}\ln \left(\frac{h}{h-b}\right)---\left(14\right)$

Further computing formula (14) obtains:

$R_{603}=\frac{h}{c}{R}^{\′}\ln \left(\frac{h}{h-b}\right)+R^{\′}\frac{d}{2c}---\left(15\right)$

Wherein, d is that rhombus 603 flows through the minor face long (see Fig. 6 c) in direction perpendicular to electric current.

Partition graph 604 is the rectangular graph of a rule, and its resistance is:

$R_{604}=R^{\′}\frac{l}{w}=R^{\′}\frac{e}{2c}---\left(16\right)$

Wherein, e is that the minor face that rectangle 604 flows through direction perpendicular to electric current is long.

In the present embodiment, the every bar of Y electrode there are 8 complete rhombus S ₆₀₃with 9 S ₆₀₂, two S ₆₀₁with two S ₆₀₄, so the figure resistance on Y electrode is:

R _y=8R ₆₀₃+9R ₆₀₂+2R ₆₀₁+2R ₆₀₄(17)

Formula (11), (12), (15) and (16) are substituted into formula (18) and obtain:

$R_y=8(\frac{h}{c}{R}^{\′}\ln \left(\frac{h}{h-b}\right)+R^{\′}\frac{d}{2c})+9\left(R^{\′}\frac{l_1}{2a}\right)+2\left(\frac{h}{2c}{R}^{\′}\ln \left(\frac{h}{h-b}\right)\right)+2\left(R^{\′}\frac{e}{2c}\right)---\left(18\right)$

Further computing formula (18) obtains:

$R_y=(9\frac{h}{c}\ln \left(\frac{h}{h-b}\right)+\frac{4d+e}{c}+\frac{9l_1}{2a})R^{\′}---\left(19\right)$

Here, because Y electrode connects lozenge diagram by ITO in the present embodiment, therefore, the square resistance of the partition graph 601,602,603 and 604 on Y electrode is all set to, and therefore, the resistance of Y electrode is:

$R_y=(9\frac{h}{c}\ln \left(\frac{h}{h-b}\right)+\frac{4d+e}{c}+\frac{9l_1}{2a})R_{\mathrm{ITO}}^{\′}---\left(20\right)$

For the lead-in wire on graph edge edge, can regard the series connection of some rectangle line segments as, its equivalent model is shown in Fig. 9, and therefore its resistance is:

$R_{\mathrm{line}}=R^{\′}\frac{l}{w}=R_{\mathrm{MO}}^{\′}\frac{l_2}{w_1}---\left(21\right)$

Wherein, represent the square resistance of edge lead-in wire, in the present embodiment, edge lead-in wire adopts metal M O.

Out, certainly also have some very little resistance at tie point, these resistance can use Δ to all resistance basic calculating on such Y electrode _rrepresent, in the present embodiment, its value is 0.

So the resistance of whole piece Y electrode is:

$R_y=(9\frac{h}{c}\ln \left(\frac{h}{h-b}\right)+\frac{4d+e}{c}+\frac{9l_1}{2a})R_{\mathrm{ITO}}^{\′}+\frac{l_2}{w_1}{R}_{\mathrm{MO}}^{\′}+{\mathrm{\Δ}}_R---\left(22\right)$

Formula (5) is substituted into formula (22) obtain:

$R_y=(9\frac{b}{c-a}\ln \left(\frac{c}{a}\right)+\frac{4d+e}{c}+\frac{9l_1}{2a})R_{\mathrm{ITO}}^{\′}+\frac{l_2}{w_1}{R}_{\mathrm{MO}}^{\′}+{\mathrm{\Δ}}_R---\left(23\right)$

For X electrode, its computing method and Y electrode similar.Owing to connecting rhombus by metal bridge in X electrode, therefore only the square resistance of the junction between rhombus need be changed to the square resistance of metal.When metal bridge uses metal M O, the square resistance of partition graph 601,603 and 604 is R ' _iTO, and the square resistance of partition graph 602 is R ' _mO.

(2) calculating of the capacitance of every strip electrode

Next, the calculating of the capacitance of every strip electrode is described.

As mentioned above, when calculating the capacitance of every strip electrode, be the capacitor equivalent model of a series of relevant capacitor parallel connection by the capacitor equivalent of every strip electrode, comprising: the electric capacity C that (1) rhombus and periphery 4 rhombuses are formed ₁, C ₂, C ₃and C ₄(as shown in Figure 10); (2) rhombus and TFT-LCD the superiors ITO(are as shown in figure 11, and TFT-LCD the superiors ITO is used for providing V for LCD _cOMsignal) between electric capacity C _lcd1; (3) figure bridging position electric capacity C ₃₀₁(as shown in Figure 3); (4) the electric capacity C between edge lead-in wire and adjacent legs _line; (5) lead-in wire and the TFT-LCD the superiors go between electric capacity C _lcd2.

In above mathematical model, these electric capacity are parallel with one another, form the stray capacitance on every strip electrode together, namely have:

C _total=4*C ₁+C _lcd1+C ₃₀₁+C _line+C _lcd2(24)

Here illustrate, in the present embodiment, when doing ITO pattern, design load is that the rhombus that each rhombus is adjacent with periphery is equidistant, so C ₁=C ₂=C ₃=C ₄.

The equivalent model of above-mentioned electric capacity is plane-parallel capacitor, is described in detail below by the computing method of each electric capacity.Before explanation, first specific inductive capacity is explained.ε ₀for vacuum absolute dielectric constant, ε _gapfor the specific inductive capacity between rhombus and four limit rhombuses, ε _lcdfor the specific inductive capacity of insulating material between TFT-LCD, ε _llinefor the electric constant between metal wire, ε _bridgefor the specific inductive capacity of the insulating material between metal bridge and pattern I TO.

Electric capacity C ₁for:

$C_1={\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{gap}}\frac{t_1*l_3}{d_2}---\left(25\right)$

Wherein, t ₁for the thickness (as shown in figure 11) of ITO pattern inductive layer, l ₃for the length of side of rhombus, d ₂for rhombus spacing (as shown in Figure 10).

C _lcd1for the parallel plate capacitor of whole lozenge diagram and TFT-LCD ITO, therefore its parallel-plate area is the area of whole rhombus, and the areal calculation of rhombus adopts partitioning scheme as shown in figure 12 to calculate, and its area is:

S _d=S ₁₀+S ₁₁+S ₁₂+S ₁₃+S ₁₄+S ₁₅-S ₁₆=4S ₁₀+S ₁₄+S ₁₅-S ₁₆(26)

Wherein, S ₁₄erect elongated rectangular shape region area for centre and (comprise central area S ₁₆), S ₁₅for centre bar region area of growing crosswise (comprises central area S ₁₆), therefore:

S _d=2b(c-a)+4a(b+d)+4dc-4ad=2ab+2bc+4cd (27)

Therefore, C _lcd1for:

$C_{\mathrm{lcd}1}={\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{lcd}}\frac{2\mathrm{ab}+2\mathrm{bc}+4\mathrm{cd}}{d_3}---\left(28\right)$

Wherein, parameter a, b, c and d are see Fig. 8, d ₃for thickness of insulating layer (see Figure 11).

Figure bridging position electric capacity C ₃₀₁for:

$C_{301}={\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{bridge}}\frac{2a*d_4}{t_2}---\left(29\right)$

Wherein, t ₂for the thickness of insulation course between pattern I TO and metal bridge, d ₄for bridge width (see Fig. 3).

Electric capacity C between edge lead-in wire and adjacent legs _linefor:

$C_{\mathrm{line}}=2{\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{line}}\frac{l_2*t_3}{d_5}---\left(30\right)$

Wherein, l ₂for the length (see Fig. 9) of edge cabling, t ₃for the coating film thickness of metal wire, d ₅for the line-spacing (see Figure 13) between metal wire.

Electric capacity C between lead-in wire and the TFT-LCD the superiors go between _lcd2for:

$C_{\mathrm{lcd}2}={\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{lcd}}\frac{l_2*d_6}{d_3}---\left(31\right)$

Wherein, l ₂for the length (see Fig. 9) of edge cabling, d ₃for thickness of insulating layer (see Figure 11), d ₆for metal wire live width (see Figure 13).

Therefore, the electric capacity of every strip electrode is total up to:

$C_{\mathrm{total}}=4{\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{gap}}\frac{t_1*l_3}{d_2}+{\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{lcd}}\frac{2\mathrm{ab}+2\mathrm{bc}+4\mathrm{cd}}{d_3}+{\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{bridge}}\frac{2a*d_4}{t_2}+2{\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{line}}\frac{l_2*t_3}{d_5}+{\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{lcd}}\frac{l_2*d_6}{d_3}+{\mathrm{\Δ}}_c---\left(32\right)$

Wherein, Δ _crepresent other stray capacitance on electrode, its value is 0 in the present embodiment.

(3) calculating of parameter τ

After the resistance value calculating every strip electrode and capacitance, the resistance value calculated and capacitance are substituted into formula (1), can obtain:

$\mathrm{\τ}=((9\frac{b}{c-a}\ln \left(\frac{c}{a}\right)+\frac{4d+e}{c}+\frac{9l_1}{2a})R_{\mathrm{ITO}}^{\′}+\frac{l_2}{w_1}{R}_{\mathrm{MO}}^{\′}+{\mathrm{\Δ}}_R)*(4{\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{gap}}\frac{t_1*l_3}{d_2}+{\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{lcd}}\frac{2\mathrm{ab}+2\mathrm{bc}+4\mathrm{cd}}{d_3}$

$+{\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{bridge}}\frac{2a*d_4}{t_2}+2{\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{line}}\frac{l_2*t_3}{d_5}+{\mathrm{\ϵ}}_0{\mathrm{\ϵ}}_{\mathrm{lcd}}\frac{l_2*d_6}{d_3}+{\mathrm{\Δ}}_c)---\left(33\right)$

When calculating, only needing the scope of the representative value of parameters/each technological parameter to substitute into formula (33), can τ be obtained _max, τ _min, τ _typical, thus the parameter of board design.

Below, for the capacitance touch screen designed by the present embodiment, provide an object lesson.In this example embodiment, design parameter is respectively: the square resistance of material aspect ITO is 55 ± 20ohm,=0.52 ± 0.15ohm, the trapezoidal upper bottom side length a=34 μm in rhombus place, go to the bottom length of side c=2696.5 μm, trapezoidal high b=2532.5 μm, the wide d=70 μm of trapezoidal place rhombus intermediate rectangular, width e=200 μm of a line electrode rim place rectangle, the long l of two rhombus junction bridges ₁=300 μm, panel edges is along the long l of lead-in wire ₂=78000 μm, panel edges is along the wide w of lead-in wire ₁=28.5 μm, Δ in the present embodiment _r=0ohm, dielectric constant of air is ε ₀=8.854*10 ^-12f/m, ε _gap=1.00053, ε _lcd=1.00053, ε _bridge=6.5, ε _line=5, induction thickness profile ITO=400A, the present embodiment is that capacitive touch screen is directly produced on color membrane substrates by Touch On-Cell() product, therefore gap d between figure to LCD ₃=0.6mm, thickness of insulating layer t ₂=6000A, bridge joint place width d ₄=20 μm, peripheral metal line lead thicknesses t ₃=2200A, lead spacing d ₅=30 μm, live width d ₆the Δ of=20 μm of the present embodiment _c=0.

Bring above-mentioned each design parameter in design formula computing and obtain τ _maxx=0.1478, τ _maxy=0.1117, τ _minx=0.0714, τ _miny=0.0557, τ _typicalx=0.0876 μ s, τ _typicaly=0.1096 μ s.

In the design process, if the τ that obtains of computing _maxbe greater than the τ required by figure _max, then only need Amending design parameter to reach designing requirement, to ensure that namely the design parameter obtained is meet manufacturing process Capability Requirement when first time, sample dropped into, also meet design needs.About the detailed process according to the parameter τ adjust design parameters calculated, belong to prior art, therefore the descriptions thereof are omitted here.

Can find out from the above description, the present invention carrys out calculating parameter τ by the method for analog simulation, just can know the film that each layer needs plating how thick when producing in advance like this at the beginning of design.And, just can the manufacturing process ability of production equipment be taken into account (such as at the beginning of design, the parameter such as thickness deviation, specific inductive capacity, ITO resistance tolerance by film forming), with the quality making the product made also can ensure product under extreme process conditions.In addition, analogy method of the present invention, not only considers the parameters of capacitance touch screen figure itself, the more important thing is, also contemplates the parameter that capacitance touch screen and TFT-LCD arrange in pairs or groups and (comprises V _cOMvoltage) design.

Correspondingly, the invention provides a kind of graphics controller of projected capacitive touch screen, it comprises parameter τ computing module, wherein, parameter τ computing module comprises resistance value computing unit, capacitance computing unit and parameter τ computing unit, and the account form of each unit is described above.

Preferably, this graphics controller also comprises parameters revision module, and it carrys out the design parameter of projected capacitive touch screen involved in corrected parameter τ computation process for the parameter τ calculated according to parameter τ computing module.As mentioned above, design parameter can comprise the parameter etc. that the structural parameters of the ITO pattern of described capacitive touch screen, the manufacturing process ability parameter of production equipment and described capacitive touch screen and TFT-LCD arrange in pairs or groups.

Reference drawings and Examples are to invention has been detailed description above, but should be appreciated that, the present invention is not limited to above disclosed exemplary embodiment.Claim should be given to explain the most widely, to contain all modification of disclosed exemplary embodiment, equivalent structure and function.

Claims (9)

1. parameter τ computing method for projected capacitive touch screen, the ITO pattern of described projected capacitive touch screen is rhombus, it is characterized in that, described method comprises:

Calculate the resistance value of every strip electrode;

Calculate the capacitance of every strip electrode; With

Obtain parameter τ by the resistance value of every strip electrode calculated being multiplied with capacitance, described τ is used for the design parameter of projected capacitive touch screen involved in corrected parameter τ computation process;

Wherein, the step of the resistance value of the every strip electrode of described calculating comprises:

The figure of every strip electrode is divided into multiple regular figure successively, and determines the equivalent resistance model of described electrode according to the position relationship of split regular figure;

Calculate the equivalent resistance of each regular figure; With

The resistance value of described electrode is calculated according to described equivalent resistance model,

Further, the step of the capacitance of the every strip electrode of described calculating comprises:

It is the capacitor equivalent model of a series of relevant capacitor parallel connection by the capacitor equivalent of every strip electrode;

For each electric capacity in described capacitor equivalent model, the model of plane-parallel capacitor is adopted to calculate its equivalent capacitance value; With

The capacitance of described electrode is calculated according to described capacitor equivalent model.

2. parameter τ computing method according to claim 1, is characterized in that, the regular figure of described segmentation comprises the non-rectangle figure of the rectangular graph Sum fanction of rule,

The step of the equivalent resistance of each regular figure of described calculating comprises:

For the rectangular graph of rule, the square resistance of the material used by this rectangular graph calculates its resistance value,

For the non-rectangle figure of rule, perform following steps:

Described non-rectangle figure is divided into the regular figure calculating its resistance value by integration method further, and determines the equivalent resistance model of described non-rectangle figure according to the position relationship of the regular figure of segmentation further;

The equivalent resistance of each regular figure of segmentation is further calculated according to described integration method; With

The equivalent resistance of described non-rectangle figure is calculated according to described equivalent resistance model.

3. parameter τ computing method according to claim 2, is characterized in that, the described regular figure calculating its resistance value by integration method comprises right-angled trapezium and rectangle.

4. parameter τ computing method according to claim 2, is characterized in that, the step of the resistance value of the every strip electrode of described calculating comprises:

The figure of every strip electrode is divided into successively the non-rectangle figure of the rectangular graph Sum fanction of multiple rules of series connection, and determines the resistance in series equivalent model of described electrode according to the position relationship of split figure;

Each rectangular graph of series connection and the equivalent resistance of non-rectangle figure is calculated respectively according to the step of the equivalent resistance of each regular figure of described calculating; With

The resistance value of described electrode is calculated according to described resistance in series equivalent model.

5. parameter τ computing method according to claim 1, is characterized in that, the capacitor equivalent model of described every strip electrode comprises: the electric capacity that rhombus and periphery 4 rhombuses are formed; Electric capacity between rhombus and TFT-LCD the superiors ITO; Figure bridging position electric capacity; Electric capacity between edge lead-in wire and adjacent legs; Electric capacity between lead-in wire and the TFT-LCD the superiors go between.

6. a graphics controller for projected capacitive touch screen, the ITO pattern of described projected capacitive touch screen is rhombus, it is characterized in that, comprises parameter τ computing module, and described parameter τ computing module comprises:

Resistance value computing unit, it calculates the resistance value of every strip electrode;

Capacitance computing unit, it calculates the capacitance of every strip electrode;

Parameter τ computing unit, it obtains parameter τ by the resistance value of the every strip electrode calculated being multiplied with capacitance; With

Parameters revision module, it carrys out the design parameter of projected capacitive touch screen involved in corrected parameter τ computation process for the parameter τ calculated according to parameter τ computing module;

Wherein, the step of the resistance value of the every strip electrode of described calculating comprises:

The figure of every strip electrode is divided into multiple regular figure successively, and determines the equivalent resistance model of described electrode according to the position relationship of split regular figure;

Calculate the equivalent resistance of each regular figure; With

The resistance value of described electrode is calculated according to described equivalent resistance model,

Further, the step of the capacitance of the every strip electrode of described calculating comprises:

It is the capacitor equivalent model of a series of relevant capacitor parallel connection by the capacitor equivalent of every strip electrode;

For each electric capacity in described capacitor equivalent model, the model of plane-parallel capacitor is adopted to calculate its equivalent capacitance value; With

The capacitance of described electrode is calculated according to described capacitor equivalent model.

7. graphics controller according to claim 6, is characterized in that, the regular figure of described segmentation comprises the non-rectangle figure of the rectangular graph Sum fanction of rule,

The step of the equivalent resistance of each regular figure of described calculating comprises:

For the rectangular graph of rule, the square resistance of the material used by this rectangular graph calculates its resistance value,

For the non-rectangle figure of rule, perform following steps:

Described non-rectangle figure is divided into the regular figure calculating its resistance value by integration method further, and determines the equivalent resistance model of described non-rectangle figure according to the position relationship of the regular figure of segmentation further;

The equivalent resistance of each regular figure of segmentation is further calculated according to described integration method; With

The equivalent resistance of described non-rectangle figure is calculated according to described equivalent resistance model.

8. graphics controller according to claim 6, is characterized in that, the capacitor equivalent model of described every strip electrode comprises: the electric capacity that rhombus and periphery 4 rhombuses are formed; Electric capacity between rhombus and TFT-LCD the superiors ITO; Figure bridging position electric capacity; Electric capacity between edge lead-in wire and adjacent legs; Electric capacity between lead-in wire and the TFT-LCD the superiors go between.

9. graphics controller according to claim 6, it is characterized in that, described design parameter comprises the parameter that the structural parameters of the ITO pattern of described capacitive touch screen, the manufacturing process ability parameter of production equipment and described capacitive touch screen and TFT-LCD arrange in pairs or groups.