JPH03294919A - Display device with tablet function - Google Patents

Abstract

PURPOSE:To eliminate the need of a special correction and to thin the thickness by utilizing X driving line orthogonal to a Y driving line of a flat display for detecting as coordinate, and constituting integrally the device by adding a tablet function. CONSTITUTION:A transparent tablet is eliminated, and an X driving line 12 and a Y driving line 13 of a liquid crystal display 1 are utilized as they are for the matrix wiring for detecting a coordinate. That is, the device consists of an input display integral type constitution which can plot and display a handwritten input position by a pen touch and an image position subjected to echo-back display in the same position by adding a tablet function of a matrix driving type liquid crystal display. Accordingly, a character, a graphic can be plotted, and simultaneously, can be displayed by a handwritten input. In such a way, a correcting circuit for a table input coordinate value is not required, and also, the thickness can be thinned.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a display device with a tablet function, and its application field is engineering workstation (EWS).
Computer-aided design (
CAD), Computer Aided Engineering (CAE), handwritten word processors, image processing functions that simultaneously draw and display input support such as character and graphic input for electronic notebooks, and telephony that simultaneously transmits handwritten and drawn images. It is used in handwriting input display devices such as writing devices and portable data entry terminals.

(Prior Art) Fig. 4 shows an example of a conventional input/display integrated display device that integrates a liquid crystal display and a transparent tablet. is a sectional view taken along line AA' shown in FIG.

As shown in figure (a), this has a structure in which a transparent tablet 2 is pasted on the top surface of a liquid crystal display 1 with a spacer t (see figure (b)). By touching the screen with a finger or finger, the input coordinate value of the pressed point is detected, and the detected information is converted into pixels of the corresponding point on the liquid crystal display and displayed. Therefore, the trajectory of the point pressed with the input pen 3 is displayed.

FIG. 4(b) is a more detailed sectional view taken along line AA' in FIG. 4(a). The method of transparent tablet is electrostatic bonding type.

There are electromagnetic induction type and pressure sensitive type. What is shown in Figure 4 is
It is a pressure-sensitive transparent tablet with a simple structure. here,
A normal transparent tablet 2 has two uniform transparent resistive films 5 on top and bottom on a transparent glass or transparent film substrate 4, and becomes electrically conductive when pressed with an input pen 3, etc., and these two transparent resistive films It has a structure in which a constant current is passed through the input terminal 5, and the current is divided in the X direction and the Y direction, respectively, and the change in the resistance value in the X and Y directions, which changes depending on the input coordinate position, is measured and the coordinate value is detected.

In addition, active matrix drive type liquid crystal display 1
In this structure, each pixel is integrated with an active element or a nonlinear element that functions as a switch element 19, and a signal storage capacitor formed by a liquid crystal layer TN, and the liquid crystal is driven quasi-statically.

A thin film transistor (TPT) is used for the switch element 19, and amorphous silicon (a
-8i) or polysilicon (poly-Si). Figure 4(b) shows amorphous silicon (a-8
This is a diagram showing one pixel of i), and its configuration is a switch element consisting of a gate electrode G, a-8i, a source electrode S, and a drain electrode. A thin film transistor TPT is formed, and a protective film is used to protect TPT. 11 are provided. The gate insulating film 10 is an insulating layer formed by the intersection of the gate electrode G and the drain electrode.

Note that the gate electrode G is a scanning line (X drive line), and the source electrode G is a data line (X drive line).

Further, since a-8i is sensitive to light and its off-state current increases if it is directly exposed to light, a light shielding layer 9 is provided thereon. When turning on and off the display, the liquid crystal layer TN is deflected by the potential difference between the counter electrode 8 and the pixel electrode 7, creating a state where light is transmitted or not, and a display is performed.

(Problems to be Solved by the Invention) In the above-mentioned conventional input display integrated display device that integrates a liquid crystal display and a transparent tablet,
When the liquid crystal display 1 and the transparent tablet 2 are bonded together, the actual input position and the displayed position will be shifted due to non-uniformity of the resistance value of the transparent resistive film 5, resulting in a coordinate detection error.

Therefore, in order to provide a one-to-one correspondence between the display position of the liquid crystal display 1 and the input position, there is a drawback that a circuit for correcting errors in the input coordinate values pressed by the transparent tablet 2 is required.

Also, when bonding the liquid crystal display 1 and the transparent tablet 2 together, if they are bonded closely together, interference fringes will occur on the ring, so countermeasures such as deflection filters and the spacing of the spacers t should be set at 0.5 to 1 m. When actually inputting with input pen 3, etc., there is a difference between the input position and the displayed position due to the thickness of the input pen, and when inputting by hand, the actual handwritten This method has the disadvantage that it is difficult to input the locus due to the deviation in its display (echo back).

In order to eliminate the above-mentioned drawbacks, there is an example of an EL display in which a capacitively coupled tablet function is integrated using the matrix wiring for driving the EL display (Masahiro Ise, Electrode/Drive Circuit) EL display with tablet function, IEICE Spring National Conference, D-211゜1989). However, if this method is directly applied to a liquid crystal display, the coordinate detection pulse is directly applied to the liquid crystal, resulting in a fatal drawback in that the display becomes distorted.

The present invention solves the problems caused by bonding a liquid crystal display and a transparent tablet constituting the input/display integrated display device of the prior art described above.

The purpose is to draw and display the handwriting input position and the display position at the same position without correction.

(Means for Solving Problem 141) The present invention solves the above problems and achieves the purpose by solving M×
N active elements or nonlinear elements are arranged two-dimensionally,
By the intersecting M X drive lines and N X drive lines that drive the M×N elements, the ○N10F of the display pixel is selectively
In a display device that performs F control, a coordinate detection period is provided for each frame or field, and during the coordinate detection period, the M and N X and X drive lines have polarities such that the M×N elements do not become conductive. A pulse voltage is sequentially applied to a contact portion between an input pen having a conductive pen tip and a display position;
The present invention is characterized in that the pulse voltage is detected through the X drive line or a capacitance between the X drive lines, and the coordinates of a contact site between the input pen and the display position are detected based on the detection timing.

(Function) The present invention utilizes orthogonal X drive lines and X drive lines of a flat display such as a liquid crystal display for coordinate detection, and has an integrated configuration with an added tablet function. A feature of this method is that it can accurately match the plotted coordinates with the coordinates of its drawing display without any special correction. Furthermore, since the thickness can be made thinner than in the prior art, parallax is small, and characters, figures, etc. actually drawn by handwriting can be drawn and displayed as if they were written on paper with a pencil.

(Embodiment) FIG. 1 shows a schematic diagram (a) showing the configuration of an embodiment of the present invention and its equivalent circuit (b). In FIG. 4(a), the same elements shown in FIG. However, they are formed within the liquid crystal layer TN, and are insulated by respective insulating layers.

As is clear from the schematic diagram of FIG. 1(a), the feature of this embodiment is that the transparent tablet 2 shown in FIG. The purpose is to use the line 13 as it is for matrix wiring for coordinate detection.

The basic principle of coordinate detection will be described below. The input pen 3 used in the present invention is conductive, and when the input pen 3 is brought into contact with the display surface of the liquid crystal display 1, the X drive line I2 or
A capacitor Cp is formed between the drive line 13 and the glass substrate 6a.

Here, when a pulse voltage is injected into the matrix wiring of the X drive line 12 or the
The drive line 13) is capacitively coupled. Therefore, the coordinates of the bent-touched region can be detected from the timing of injecting the pulse voltage for coordinate detection into the matrix wiring and the timing of detecting the pulse voltage 6 by the input pen.

In this way, in the present invention, the input pen 3 and the matrix arrangement, i
! Since it is necessary to utilize capacitive coupling between (X drive lines 12 and 13), the glass substrate 6a on which the matrix wiring is formed is on the front side of the liquid crystal display 1. That is, the structure of the display section is the same as the liquid crystal display 1 shown in FIG. 4(b), but as shown in FIG. 1(a), the glass substrate 6b of the counter electrode 8 is located on the back side of the display surface. , the glass substrate 6a on the matrix wiring side is on the front side. If the counter electrode 8 side is the front surface, the counter electrode 8 becomes an electrostatic shield, and the matrix wiring and the input pen 3 are not capacitively coupled. In Figure (a), the X drive line 12 is a drive line perpendicular to the page, and the X drive line is a drive line horizontal to the page, indicating a crossover section via the insulating layer K. TFTs formed on the same substrate are omitted.

FIG. 1(b) is an equivalent circuit of the capacitive coupling part between the matrix wiring and the input pen 3, where Ep is the injection pulse voltage to the matrix wiring, Cp is the capacitance between the input pen 3 and the matrix wiring, and Ce is the input pen 3 and the ground, Re is the resistance between the input pen 3 and the ground, and if Re>1/ωCe, the pen voltage Vp induced in the input pen 3 is Vp=E
It becomes p-Cp/(Cp+Ce). By detecting this voltage Vp, the coordinates of the bent-touch site can be detected.

FIG. 2 shows a circuit diagram of the display device with tablet function shown in FIG. 1, and FIG. 3 is a timing chart explaining its operation.

Figure 2 shows the case of M x N pixels (bits).
4 is an M-bit X driver, 15 is an N-bit Y driver, 16 is a switching control circuit for X and Y drivers 14.15,
17 is a display control circuit into which display data D1 is input; 18
is a coordinate inspection circuit that outputs coordinate data D2. Here, the TFT of the switch element 19 located at the intersection of the matrix wiring (X, Y drive lines 12, 13) is
This example shows a type that turns on when (gate voltage) is positive. Therefore, when displaying, from the X driver 15 to the Y drive line 1
Apply a positive pulse voltage to 3 (scanning line) to turn on the TPTs one line at a time, and apply a pulse voltage to each TPT according to the display data D1 input from the X driver 14 for one line. .

On the other hand, in coordinate detection, the switching control circuit 16 switches the control of the X driver 14 and the X driver 15 to the display control circuit 17 during the blanking period of one field or one frame.
Then, the coordinate detection circuit 18 is switched to the coordinate detection circuit 18 for execution. here,
Since the output to the Y drive line 13 is a negative pulse and the TPT is not turned on, the voltage applied to the liquid crystal does not change. This allows the pulse voltage for coordinate detection to be applied to the X drive line 12.
Even if it is injected into the Y drive line 13, the displayed image will not be disturbed. Although the X driver 15 needs to output pulses of both positive and negative polarities, it may have the same circuit configuration as the X driver 14. That is, the X driver 14 is AC driven to prevent deterioration of the liquid crystal, and the polarity of its output is reversed for each field or frame.

FIG. 3 is a timing chart of FIG. 2.

The blanking signal represents a non-display period such as the vertical synchronization signal VSYNC and a back porch period, and one coordinate detection operation is completed during this blanking period. That is,
During this period, coordinate detection pulses are sequentially injected into the drive lines X1 to Xn and Yl to Yn. Here, if the input pen 3 is at the position (X2.Y2) of the matrix wiring,
Coordinate detection pulse X2 in FIG. The pen voltage VP synchronized with Y2 is input to the coordinate detection circuit 18. At this time, the value of the counter that counts the shift clock (not shown) of the coordinate detection pulse is X2. Y2, and this value corresponds to the coordinates of the input pen 3. The operation of 0 or more is repeated for each field or frame to obtain continuous coordinate data D2. At this time, the field or frame frequency is 50~
607, the coordinate detection speed is 50 to 60 samples/second, which is sufficient to follow the speed of normal handwritten input.

Note that the capacitance CP between the X or Y drive line 12, 13 and the input pen 3 is a fairly small capacitance, and the induced pen voltage Vp is low and there is a high possibility that a detection error will occur. As one method for solving this problem, it is also possible to apply a coordinate detection pulse to a plurality of drive lines at the same time. In this case, the sum of the individual capacitances between the simultaneously applied drive line and the input pen becomes the effective coupling capacitance, increasing CP and S
/N improves.

(Effects of the Invention) As explained above, according to the present invention, a tablet function is added to a matrix-driven liquid crystal display, and a drawing is displayed at the same position as the position of handwritten input by pen touch and the position of the image displayed on the echo pack. It has an integrated input and display configuration that allows you to

Therefore, characters and figures can be drawn and displayed at the same time with one handwritten input, and compared to conventional technology, there is no need for a correction circuit for tablet input coordinate values, and the thickness can be made thinner. This has the advantage that the error between the position and the display position of the echo pack can be reduced, and an integrated input and display device with excellent man-machine interface can be realized.

In addition, conventionally, light was absorbed by a transparent tablet, resulting in a decrease in light transmittance, but the present invention eliminates the need for a transparent tablet dedicated to coordinate detection, resulting in improved light transmittance and excellent display contrast. It is economical because there is no need to form a tablet plane.

In the above description, a TN type liquid crystal was used as an example of a flat display, but the present invention is not limited to this, and may be applied to liquid crystals other than TN type (STN, GH, ferroelectric type, etc.), EL, It is also applicable to active matrix flat displays such as plasma. Further, although an example has been described in which TPT is applied as an element at the intersection of matrix wiring, the present invention is applicable to general nonlinear elements having a switching function, and M I M (Me
tal-Insulator-Metal), B B
D (Back to Back Diode), RO
(Ring Diode), T D S D (Tw.

D 1odes S witching D evic
e) It is applicable to various well-known active matrix liquid crystal displays such as varistor type liquid crystal displays. That is, X
Only when the selection signal is input to the drive line and the X drive line at the same time,
If the element at the matrix intersection is an element that turns on, coordinate detection pulses may be sequentially injected into the X drive line or the X drive line, and the other drive line may be set to a non-selected potential at which the matrix intersection element does not turn on.

[Brief explanation of drawings]

FIG. 1(a) is a schematic diagram showing the configuration of an embodiment of the present invention,
FIG. 1(b) is a diagram showing an equivalent circuit, FIG. 2 is a circuit configuration diagram of the display device with tablet function shown in FIG. 1, FIG. 3 is an operation timing chart of FIG. 2, and FIG. ) is an external view showing an example of a conventional input/display integrated display device, and is a sectional view taken along line AA' in the figure. 1...Liquid crystal display, 3...Input pen,
6...Glass substrate (6a, 6b), 7...
Pixel electrode, 8... Counter electrode, 9... Light shielding layer, 10... Gate insulating film, 11... Protective film, 12
...X drive line, 13...X drive line, 14...X driver, 15...Y driver, 16...switching control circuit, 17...display control circuit, 18...coordinates detection circuit. 19...Switch element, TPT...Thin film transistor, a-8i...Amorphous silicon, G
...Gate electrode, S...Source electrode, D...
- Drain electrode, TN...liquid crystal layer, K...insulating layer. Figure 4(b) is (a)

Claims (1)

[Claims] M×N active elements or nonlinear elements are arranged two-dimensionally, and M×N intersecting X drive lines and N Y drive lines drive the M×N elements. , selectively turn on/off display pixels
In a display device that performs OFF control, a coordinate detection period is set for each frame or field, and
During the coordinate detection period, a pulse voltage of a polarity that does not cause the M×N elements to be in a conductive state is sequentially applied to the M and N X and Y drive lines, and the pen is displayed as an input pen having a conductive tip. Detecting the pulse voltage through a capacitance between a contact point with the position and the X drive line or the Y drive line, and detecting the coordinates of the contact point between the input pen and the display position based on the detection timing. A display device with tablet functionality featuring: