JP3342523B2 - Tablet device with display function - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tablet device having a display function added to a so-called tablet device used for inputting characters, figures and the like to a personal computer or a word processor.

[0002]

2. Description of the Related Art As a means for inputting handwritten characters and figures into a computer or a word processor, for example, a liquid crystal display and an electrostatic induction type tablet are laminated, and characters and figures are written on a paper as if by an operator with a writing instrument. An input device capable of inputting to an electrostatic induction tablet has been put to practical use.

Conventionally, as an electrostatic induction type tablet used for such an application, a transparent electrode in the form of a stripe made of indium oxide or the like is formed on a transparent glass or plastic film, and a pulse voltage is applied to the transparent electrode. In general, the tablet is scanned by sequentially applying the voltage. Such an electrostatic induction type tablet has, for example, a configuration as shown in FIG.

A coordinate input unit 1 of this electrostatic induction type tablet
Is a glass substrate 2 on which transparent electrodes X1, X2, X3,..., Xm (hereinafter, an arbitrary transparent electrode is described as X) are formed;
The transparent electrodes Y1, Y2,..., Yn (hereinafter, any transparent electrode is referred to as Y
And the glass substrate 3 on which the electrodes are formed are disposed at a small interval such that the electrode forming surfaces face each other. The coordinate input unit 1 thus formed is used by being placed on a liquid crystal display (not shown).

The transparent electrodes X and Y are connected to a column electrode shift register 4 and a row electrode shift register 5, respectively.
These two shift registers 4 and 5 are connected to a timing generation circuit 6. This timing generation circuit 6 sends shift data and a clock signal to each of the shift registers 4 and 5. Then, based on the shift data and the clock signal, the column electrode shift register 4 sequentially applies a pulse voltage to the transparent electrodes X1, X2,..., Xm.
The row electrode shift register 5 includes electrodes Y1, Y2,.
A pulse voltage is sequentially applied to n.

When the tip of a designated coordinate detection pen (hereinafter simply referred to as a detection pen) 7 is brought close to the surface of the coordinate input section 1, an electrode provided at the tip of the detection pen 7 and a transparent electrode X are provided.
Alternatively, a voltage is induced at the electrode at the tip of the detection pen 7 due to the stray capacitance between the transparent pen Y and the transparent electrode Y. The voltage induced in the detection pen 7 is amplified by the amplifier 8 and input to the X coordinate detection circuit 9 or the Y coordinate detection circuit 10.

The X-coordinate detection circuit 9 and the Y-coordinate detection circuit 10 calculate the X coordinate or the Y coordinate of the tip of the detection pen 7 based on the induced voltage signal from the amplifier 8 and the timing signal from the timing generation circuit 6, respectively. calculate. Then, the X coordinate detection circuit 9 outputs an X coordinate signal representing the X coordinate of the tip of the detection pen 7. On the other hand, the Y coordinate detection circuit 10
Outputs a Y coordinate signal representing the Y coordinate of the tip of the detection pen 7. Then, based on the X / Y coordinate signals from the X coordinate detection circuit 9 and the Y coordinate detection circuit 10, the liquid crystal display displays a pixel located at the coordinates specified by the tip of the detection pen 7.

In the case of an input device constructed by stacking the electrostatic induction type tablet and the liquid crystal display that operate as described above, the portion of the coordinate input section 1 where the transparent electrodes X and Y exist and where the transparent electrodes X and Y do not exist. Since the reflectance and the transmittance are different, grid-like electrodes can be seen on the display screen of the liquid crystal display located on the lower side, which causes deterioration in the quality of the liquid crystal display.

In view of the above, as a tablet which eliminates such disadvantages, a display-integrated tablet device as shown in FIG. 6 has recently been proposed (Japanese Patent Application No. 4-19064).

This display-integrated tablet device serves both as a display electrode of a liquid crystal display and a coordinate detection electrode of an electrostatic induction tablet device. Then, the coordinate detection and the image display are performed in a time division manner as shown in FIG.

In FIG. 6, a liquid crystal panel 11 has common electrodes Y _{1 to} Y _n (hereinafter, an arbitrary common electrode is described as Y) and segment electrodes X _{1 to} X _m arranged orthogonally to each other.
(Hereinafter, an arbitrary segment electrode is described as X) and a liquid crystal is interposed therebetween, and each pixel is formed in a region where each common electrode Y and the segment electrode X intersect. That is, the liquid crystal panel 1 has pixels of n × m dots arranged in a matrix.

This display-integrated tablet device has the advantage of eliminating the grid-like electrode pattern and making it easier to see, as compared with the above-described liquid crystal display on which an electrostatic induction type tablet is laminated. Since the electrode and the drive circuit are also used as the induction type tablet, there is an advantage that the cost can be reduced and the size and weight can be easily reduced.

The above-mentioned display-integrated tablet device operates as follows. That is, the common drive circuit 12 for driving the common electrode Y and the segment drive circuit 13 for driving the segment electrode X are connected to the display control circuit 15 and the detection control circuit 16 via the switching circuit 14. Have been. The switching circuit 14 includes the control circuit 1
7 during the display period.
Is output to the common drive circuit 12 and the segment drive circuit 13 while the output from the detection control circuit 16 is output to the common drive circuit 12 and the segment drive circuit 13 during the coordinate detection period. In FIG. 6,
The common drive circuit 12, the segment drive circuit 13, the switching circuit 14, the display control circuit 15, the detection control circuit 16, and the control circuit 17 are represented by being divided into respective blocks.
However, in an actual circuit, each of the above circuits is an LSI
(Large-scale integrated circuit), and cannot be strictly divided into the above-mentioned blocks in terms of form.

In the display period, the display control circuit 1
5, the shift data s is output from the shift data output terminal S, the inverted signal fr is output from the inverted signal output terminal FR, the clock signal cp1 is output from the clock output terminal CP1, and the clock signal cp2 is output from the clock output terminal CP2.
There is output, the display from the data output terminal D0~D3 data D ₀ to D ₃ is output.

The clock signal cp1 is a clock signal having a period of displaying pixels of one row as a cycle. The clock signal cp1o is output via the output terminal CP10 of the switching circuit 14.
The clock input terminal YCK of the common drive circuit 12 and the latch pulse input terminal XLP of the segment drive circuit 13
Entered as The shift data s, which is a pulse signal for selecting a specific common electrode Y, is supplied to the shift data input terminal DIO1 of the common drive circuit 12 as the shift data so via the output terminal SO of the switching circuit 14, and the clock signal cp1o. Input in synchronization with.

The shift data so
Is input, the pulse position of the shift data so is shifted by the shift register in synchronization with the clock signal cp1o, and the common drive circuit 1 corresponding to the shift position is shifted.
Driving pulses of common electrode drive signal is applied from the second output terminal O1~On common electrodes Y ₁ to Y _n. The common electrode drive signal is generated based on the bias power supply V ₀ ~V ₅ supplied from the DC power supply circuit 22.

The clock signal cp2 is a clock signal having a cycle of a period obtained by dividing a period for displaying pixels of one row into several parts, and is output as a clock signal cp2o via the output terminal CP2O of the switching circuit 14 to the segment driving circuit 13. Is input to the clock input terminal XCK.

The display data D _{0 to} D ₃ are transmitted to the switching circuit 1
Display data D ₀ through the output terminal D0O~D3O of 4 O ~
Input terminal of the segment driving circuit 13 as the D ₃ o XD0~
The signal is input to the XD 3 and sequentially taken into a register in the segment drive circuit 13 in synchronization with the clock signal cp2o. When all the display data corresponding to the pixels for one row is captured, the captured display data is latched at the timing of the clock signal cp1o input to the latch pulse input terminal XLP, and the display data corresponding to each display data is latched. The driving pulse of the segment electrode driving signal is
Is applied from the output terminal O1~Om to the segment electrodes X ₁ to X _m. This segment drive signal is also supplied to the DC power supply circuit 22.
It is generated based on the bias power supply V ₀ ~V ₅ supplied from.

The inversion signal fr is a signal for periodically inverting the application direction of the voltage applied to the liquid crystal during the display period to prevent the liquid crystal from being deteriorated by electrolysis.
The inversion signal fro is input to the inversion signal input terminal YFR of the common drive circuit 12 and the inversion signal input terminal XFR of the segment drive circuit 13 via the inversion signal output terminal FRO of the switching circuit 14.

The operation of the common drive circuit 12 and the segment drive circuit 13 causes the liquid crystal panel 11 to operate.
Are driven according to their row order,
An image corresponding to the display data D _{0 to} D ₃ is displayed on the liquid crystal panel 11.

On the other hand, during the coordinate detection period, the shift data sd is output from the shift data output terminal Sd of the detection control circuit 16, the inverted signal frd is output from the inverted signal output terminal FRd, and the clock signal is output from the clock output terminal CP1d. cp1d is output, the clock signal cp2d is output from the clock output terminal CP2d, and the data output terminals D0d to
Drive data D ₀ d~D ₃ d is output from the d3d.

The clock signal cp1d is a clock signal having a period of a scanning period for scanning one common electrode Y, and is output as a clock signal cp1o via the output terminal CP10 of the switching circuit 14 to the clock input terminal of the common drive circuit 12. YCK and the latch pulse input terminal XLP of the segment drive circuit 13 are input. Also, a specific common electrode Y
Shift data sd, which is a pulse signal for selecting
Shift data via the output terminal SO of the switching circuit 14
shift data input terminal D of the common drive circuit 12 as so
It is input to IO1 in synchronization with the clock signal cp1d.

Then, as in the above-described display period, the pulse position of the shift data so is shifted by the shift register of the common drive circuit 12 in synchronization with the clock signal cp1o, and the output terminal O corresponding to the shift position is shifted.
The common electrode scanning signal y ₁ ~y _n (hereinafter, an arbitrary common electrode scanning signal to as y) to the common electrode Y ₁ to Y _n from 1~On scan pulse is sequentially applied. The common electrode scanning signal y is generated based on the bias power supply V ₀ ~V ₅ supplied from the DC power supply circuit 22. The above clock signal
cp2d is a clock signal whose cycle is a scanning period for scanning the segment electrode X, and is input to the clock input terminal XCK of the segment drive circuit 13 as the clock signal cp2o via the output terminal CP2O of the switching circuit 14.

The driving data D ₀ d to D ₃ d are supplied to the driving data D ₀ o via output terminals D 00 to D ₃₀ of the switching circuit 14.
To D ₃ o as the input terminal XD0 of the segment drive circuit 13.
To XD3, and sequentially taken into a register in the segment drive circuit 13 in synchronization with the clock signal cp2o.
Then, the scanning pulse of the segment electrode scanning signals x _{1 to} x _m (hereinafter, an arbitrary segment electrode scanning signal is referred to as x) corresponding to the above-described drive data is applied to the segment driving circuit 13.
Is output from the output terminal O1~Om to the segment electrodes X ₁ to X _m. The segment electrode scanning signal x is also generated based on the bias power supply V ₀ ~V ₅ supplied from the DC power supply circuit 22. The input of the drive data D ₀ o~D ₃ o to the segment driving circuit 13 in the coordinate detection period may also be implemented separately from the input terminal provided to the input terminal XD0～XD3.

The coordinate detection period is divided into an x-coordinate detection period and a subsequent y-coordinate detection period. In the x-coordinate detection period, a segment voltage scanning signal x, which is a pulse voltage signal, is sequentially applied to the segment electrodes X. During the y coordinate detection period, a common voltage scanning signal y, which is a pulse voltage signal, is sequentially applied to the common electrode Y.

By applying the pulse voltage signal, the segment electrode X or the common electrode Y and the designated coordinate detecting pen
A voltage is induced in the detection pen 18 by a stray capacitance between the detection pen 18 (hereinafter, simply referred to as a detection pen) and the tip electrode. The induced voltage generated in the detection pen 18 is amplified by the amplifier 19 and input to the x-coordinate detection circuit 20 and the y-coordinate detection circuit 21. The x-coordinate detection circuit 20 and the y-coordinate detection circuit 21 are connected to the output signal from the amplifier 19 and the control circuit 1.
7 to detect the time from when the pulse voltage signal is applied to when the induced voltage reaches the maximum value, thereby detecting the x-coordinate or y-coordinate of the position indicated by the detection pen 18, respectively. Is detected.

The input device and the display-integrated tablet device (see FIG. 6) in which the electrostatic induction type tablet (see FIG. 5) is laminated on the above-mentioned liquid crystal display use the electrostatic induction type tablet, so that the electromagnetic induction type tablet is used. Compared to the case of using a tablet of the system, the power consumption is small, the structure is simple, and the device is resistant to external and internal magnetic noise. Therefore, it is widely used as a powerful means of handwriting input, particularly in portable devices.

However, as described above, in the electrostatic induction type tablet, the tip coordinates of the detection pen are detected by an induced voltage generated in the detection pen when a scanning pulse is applied to the detection electrode. Therefore, malfunction may occur when there is an electrostatic noise source near the tip electrode of the detection pen.

In particular, when a liquid crystal is used as the image display means in the case of a display-integrated tablet device, the output from the upper electrode (ie, the segment electrode X in FIG. 6) when viewed from the detection pen side. Since the electric field is large, the induced voltage generated in the detection pen is also large. However, the output electric field from the lower electrode (that is, the common electrode Y in FIG. 6) is a leak electric field from the gap between the upper electrodes. The induced voltage generated in the detection pen is small and is smaller by one to two orders of magnitude than the induced voltage based on the output electric field from the upper electrode. Therefore, the amplification factor of the induced voltage in calculating the y coordinate must be increased, and the calculated y coordinate value is more susceptible to the same noise than the calculated x coordinate value.

In general, a liquid crystal panel does not emit light by itself. Therefore, a clear display can be obtained outdoors in the daytime or under illumination, but it is difficult to see the display in a dark place. Therefore,
In order to obtain a clear display even in a dark place, a light source called a backlight is usually installed on the back of the liquid crystal panel in many cases. FIG. 8 is a cross-sectional view of a display-integrated tablet device in which a thin fluorescent lamp as a backlight is attached to the liquid crystal panel having the tablet function.

In FIG. 8, the liquid crystal panel 11 around which the segment drive circuit and the common drive circuit (both not shown) are provided is covered by a front panel 33 and an input panel 34. The surface of the input panel 34 and the surface of the liquid crystal panel 11 are arranged with an air layer of 1 to 3 mm. The input panel 34 is formed of, for example, a transparent acrylic plate. The surface of the input panel 34 is reinforced so as not to be damaged by the detection pen 31. In some cases, processing is performed.

On the rear surface of the liquid crystal panel 11, a plastic lamp holder 35 for accommodating the fluorescent lamp 40, a light guide plate 37 for guiding the light of the fluorescent lamp 40 from the side to the rear surface of the liquid crystal panel 11, and a scattering plate 36 are provided. I have. Also,
The output light from the fluorescent lamp 40 is efficiently transmitted to the liquid crystal panel 11.
Inside the lamp holder 35 and the light guide plate 37
Are provided with reflection plates 41 and 42 on the back of the. Furthermore, bottom plate 3
On the side of 9, a lead wire to the electrode of the fluorescent lamp 40 and a lamp driving power supply (both not shown) are arranged. FIG.
Uses a fluorescent lamp 40 as a backlight, but in order to make the device thinner, an EL (electro
It is also possible to use a (Luminescence) panel.

[0033]

As described above, the driving voltage of a fluorescent lamp or EL used as a backlight is generally high, and is about 100 V (400 Hz) in the case of EL, but several hundreds in the case of a fluorescent lamp. It reaches V. Further, when the lighting frequency of the fluorescent lamp is close to the display frame frequency of the liquid crystal panel or when it is an integral multiple, flicker occurs due to the difference. Therefore, the lighting frequency is set to several tens
In many cases, Hz is selected.

The lighting frequency is set in view of the effect on the image display and the efficiency. When the lighting frequency is high and the applied voltage is high, the lighting frequency is set close to the light source and its introduction line. A high frequency electric field is generated as shown in FIG. When this high-frequency electric field acts on the detection electrode 32 of the detection pen 31 having a high impedance, an electrostatic induction voltage is generated at the detection electrode 32. This electrostatic induction voltage is noise for the detection pen 31, thereby detecting erroneous coordinates.

As described above, the electrostatic noise causes a reduction in the detection accuracy of the coordinates of the tip of the detection pen. Therefore, it is necessary to select a component that operates at a voltage as low as possible and to consider the arrangement of the component.

That is, when the light source, lead wire, and power supply circuit of the backlight are located on the back of the central portion of the liquid crystal panel when viewed from the input surface, the display / scan electrodes X and Y themselves become shielding electrodes. Has no effect on the detection pen. However, when the liquid crystal panel 11 is located at the periphery of the liquid crystal panel, a large induced voltage is generated at the detection electrode 32 of the detection pen 31 by the high-frequency electric field wrapping around the liquid crystal panel 11 as shown in FIG. Therefore, it is desirable to arrange the backlight-related components (fluorescent lamp, lead wire, power supply circuit, etc.) so as to be hidden behind the liquid crystal panel when viewed from the input operation side.

When the display-integrated tablet device is actually operated, the induced voltage of the detection pen caused by the scanning voltage applied to the lower electrode of the common electrode group or the segment electrode group when viewed from the detection pen is small. It is about 2-3 mV. On the other hand, when a fluorescent lamp is used as a backlight, a voltage of about 100 mV is induced in the detection pen when the detection pen is placed around the liquid crystal panel.
This is because a fluorescent lamp, a power supply unit for lighting the fluorescent lamp and a lead wire are located near the detection pen, and a high-frequency electric field generated from the fluorescent lamp and the power supply unit acts thereon.

Therefore, under such an S / N condition, detection cannot be performed at all without being limited to a range of mere reduction in detection accuracy. A fluorescent lamp cannot be used as a backlight. This is the same when the EL panel is used as the backlight. In addition, the present invention can be applied not only to the display-integrated tablet device shown in FIG. 6, but also to an input device configured by stacking an electrostatic induction tablet and a liquid crystal display as shown in FIG.

An object of the present invention is to provide a tablet device with a display function that can prevent a malfunction at the time of coordinate detection caused by a high-frequency electric field from a voltage application unit and a light emitting source using an AC voltage as a backlight. is there.

[0040]

According to a first aspect of the present invention, there is provided a display panel having a first electrode group and a second electrode group arranged in different directions. Indicating means electrostatically coupled to the second electrode group to indicate the position of the display panel; first driving means for driving the first electrode group; second driving means for driving the second electrode group; Control for setting a display period for displaying on the display panel by controlling the first driving unit and the second driving unit and a coordinate detection period for performing coordinate detection based on an output signal guided by the instruction unit in a time-sharing manner. A tablet device with a display function having a display function and a tablet function integrally formed, the irradiation means being lit by an AC voltage to irradiate the display panel; and applying an AC voltage to the irradiation means. The above irradiation hand And a voltage applying means for lighting said control means, while said illumination means is turned in the display period, so that the illumination means is not lit in the coordinate detection period, and, the voltage applied manually
After stopping the application of AC voltage from the stage to the irradiation means
Start electrode scanning for coordinate detection after a predetermined time has elapsed
On the other hand, at a predetermined time after the electrode scanning for coordinate detection ends
After the passage of time, the alternating current from the voltage application unit to the irradiation unit
The voltage application means is configured to be controllable so as to start applying a voltage .

Further, the second invention is a display function tablet device of the first aspect of the invention, the frequency of the AC voltage applied from above SL voltage applying means to the irradiating means, the instruction manual
What is the frequency band of the frequency component of the induced voltage induced in the stage
A different frequency is set .

Further, the third invention is directed to the first or second embodiment .
In the tablet device with a display function according to the present invention,
From the voltage applying means based on the control signal from the means.
Start voltage and stop voltage of AC voltage applied to irradiation means
Start and stop application to control the stop voltage to be 0 volts
A voltage control means is provided .

[0043]

In the first aspect of the present invention, during the display period, the first driving means and the second driving means are controlled by the control means to display an image on the display panel. At this time, an AC voltage is applied from the voltage application unit to the irradiation unit, the irradiation unit is turned on, and the display panel is irradiated. Next, in the coordinate detection period
Is the first driving means or the second driving means depending on the control means.
Is controlled to sequentially scan each electrode group. And instructions
Instruction based on the output signal induced and output by the means
The coordinates on the display panel indicated by the means are detected.
You. At that time, the voltage is applied from the voltage application unit to the irradiation unit.
The AC voltage is stopped and the irradiation means is turned off.

Thus, during the coordinate detection period, the voltage
The application means and the irradiation means are stopped, and the voltage application means and
No high frequency electric field is generated from the irradiation means. Therefore,
The coordinates of the pointing means on the display panel are correctly detected.

Further, the voltage application means is controlled by the control means.
Is controlled so that the transition from the display period to the coordinate detection period
The application of AC voltage from the voltage application means to the irradiation means
Electrode for coordinate detection after a predetermined time elapses after stopping
Scanning starts. On the other hand, from the coordinate detection period to the display period
When shifting, electrode scanning for coordinate detection is completed
From the voltage application means to the irradiation means
Of the AC voltage is started. Therefore, the above voltage
“ON / OFF” of the AC voltage applied from the application unit to the irradiation unit
Off timing is outside the electrode scanning period for coordinate detection
Is set to “ON / OFF” for the AC voltage
During the coordinate detection period.
No noise is generated.

Further, in the second invention, the above-mentioned instruction means is used.
When an instruction is given on the display panel, an induced voltage
The display panel of the indicating means is induced based on the induced voltage.
The coordinates on the file are detected. At that time, the above display panel
Apply from the voltage application unit to the irradiation unit that irradiates from a predetermined direction
The frequency of the AC voltage to be applied is induced by the indicating means.
To a frequency different from the frequency band of the frequency component of the induced voltage
Is set. Therefore, the irradiation means and the voltage mark
Induced by the indicating means by the high-frequency electric field from the adding means
The electrostatic noise superimposed on the induced voltage is
Is reliably separated from the frequency components. Thus, during the coordinate detection period, the coordinates of the pointing means on the display panel are correctly detected.

In the third invention, the application start / stop voltage
The control means controls the control signal based on the control signal from the control means.
And an alternating current applied from the voltage applying means to the irradiating means.
And the application start voltage and the applied stop voltage of the voltage becomes "0" bolt
Is controlled as follows. Thus, the irradiation unit is turned on.
The noise generated at the time of "/ off" is suppressed.

[0048]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments. As described above, in the display-integrated tablet device shown in FIG. 6, when a fluorescent lamp that is normally lit by high frequency / high voltage of several hundred V and several tens kHz is used as the backlight, electrostatic noise of about 100 mV is used. Is induced in the detection pen. On the other hand, when the lower electrode (the common electrode in FIG. 6) is scanned during the coordinate detection period, the induced voltage induced on the detection electrode of the detection pen is about 3 mV. The effect of voltage on coordinate detection is significant.

<First Embodiment> In order to avoid such an influence of the backlight lighting voltage, in this embodiment, FIG.
In addition, the lighting frequency of the backlight in the display-integrated tablet device shown in FIG. 8 is set to a frequency sufficiently distant from the frequency band of the frequency component of the induced voltage induced in the detection pen. The numbers of the components of the display-integrated tablet device in each embodiment described below use the numbers of the components shown in FIG.

The x-coordinate detection circuit 20 and y
The frequency band of an amplifier (not shown) provided in the coordinate detection circuit 21 is adjusted to the frequency band of the frequency component of the induced voltage induced in the detection pen 18, while the lighting frequency of the backlight is sufficiently separated from the frequency band of the amplifier. Set the frequency to For example, the optimum frequency band of the amplifiers of the x-coordinate detection circuit 20 and the y-coordinate detection circuit 21 is 30 kHz to 100
In the case of kHz, the lighting frequency of the backlight is set to 3 kHz.
It is set to about Hz. By doing this,
Most of the electrostatic noise components from the backlight and peripheral circuits superimposed on the detection signal from the detection pen 18 can be removed by the amplifier. The above embodiment is also applicable to an input device configured by laminating the electrostatic induction tablet and a liquid crystal display.

<Second Embodiment> This embodiment eliminates generation of a high-frequency electric field from the above-mentioned backlight and voltage applying section and completely eliminates electrostatic noise. In the display-integrated tablet device shown in FIG. 6, as shown in FIG. 7, the display period and the coordinate detection period are alternately time-divided and driven. At this time, it is necessary to irradiate the liquid crystal panel 11 with the backlight only during the display period. Therefore, in the present embodiment, as shown in FIG. 3, the backlight is supplied with power only for the display period to turn on the backlight, and during the coordinate detection period, the power supply to the backlight is stopped and turned off.

In the display integrated type tablet device, 1
In the time distribution between the display period and the coordinate detection period in the frame period, the display period is 95% or more, and the coordinate detection period is shorter than 5%, and the display period is much longer. Therefore, even if the backlight is turned off for several hundreds of microseconds allotted for the coordinate detection period, the backlight is immediately turned on when a lighting voltage is applied to the backlight during the subsequent display period. As a result, there is no support for displaying an image on the liquid crystal panel 11 during the display period, and no electrostatic noise is generated by the high frequency electric field of the backlight lighting voltage during the coordinate detection period. That is, according to the present embodiment, the coordinates of the tip of the detection pen 18 can be accurately detected.

At this time, the following measures are taken in order to further exert the above-mentioned effects. That is, the lighting voltage to the backlight is turned on by the switching circuit.
When performing “/ off” control, electrostatic noise is likely to occur if the “on / off” timing is near the peak of the AC voltage value to the backlight. In the coordinate detection period, the switching circuit is turned off at the same time as the coordinate detection period, the backlight is turned off, and scanning of the segment electrode X or the common electrode Y is started after a predetermined time has elapsed after the light is turned off. Is to terminate the scanning of the segment electrode X or the common electrode Y a predetermined time before the display period, and turn on the switching circuit to turn on the backlight at the same time as the display period. During the coordinate detection period, the switching circuit is turned on / off.
Since "OFF" is not performed, no electrostatic noise is generated during the coordinate detection period.

When the backlight is realized by a fluorescent lamp, the "off" timing of the switching circuit may be performed immediately before the transition from the display period to the coordinate detection period. In this case, even if the switching circuit is turned off and the discharge of the fluorescent lamp is stopped, the light emission state is maintained for a short time due to the afterglow characteristic of the phosphor, so that the image display is not affected. Further, the detection of coordinates by the detection pen 18 has almost no effect.

<Third Embodiment> The above-described problem of controlling the lighting voltage to the backlight to "ON / OFF" by the switching circuit can be avoided by controlling the backlight driving device. FIGS. 1 and 2 are schematic block diagrams of a backlight drive unit having a function of turning on the backlight during the display period and turning off the backlight during the coordinate detection period. 1 and 2, the backlight voltage application circuits 52 and 54 are inverter circuits that internally include an oscillation circuit and a step-up transformer (both are not shown) and turn on the backlight 51. The backlight voltage application circuits 52 and 54 operate with the DC voltage supplied from the power supply circuits 53 and 55.

A control signal supplied from the control circuit 17 in the display-integrated tablet device shown in FIG. 6 is input to the backlight voltage application circuit 52 or the power supply circuit 55. The supply timing of the control signal can be shifted to some extent by an additional circuit.

In the first example shown in FIG. 1, the start / end of the oscillation circuit in the backlight voltage application circuit 52 is controlled by the control signal, whereby the backlight 51 is controlled.
To control the phase of the AC voltage supplied to. Therefore, as shown in FIG. 4, the AC voltage for lighting the backlight can be raised at 0 volt and stopped at 0 volt, and no noise is generated when the backlight 51 is turned on / off.

In the second example shown in FIG.
Is provided with a control function to turn on / off the DC voltage supplied to the backlight voltage application circuit 54. Therefore, the output of the oscillation circuit of the backlight voltage application circuit 54 also rises with the rise of the voltage supplied from the power supply circuit 55, so that the lighting voltage of the backlight 51 rises at 0 volt as shown in FIG. Similarly, the output of the oscillation circuit is stopped at the fall of the voltage supplied from the power supply circuit 55, so that the lighting voltage of the backlight 51 is stopped at 0 volt as shown in FIG. Therefore, no noise is generated when the backlight 51 is turned on / off.

In the third example, a semiconductor switching circuit is provided between the backlight and the backlight voltage application circuit. Then, the backlight voltage application circuit is always driven, and the switching circuit is "on / off" controlled by a control signal supplied from the control circuit 17 in the display-integrated tablet device shown in FIG. Turns on / off. At that time, as shown in FIG. 4, the AC voltage supplied to the backlight is switched on / off at 0 volt, and the backlight is operated as a so-called "zero cross switch". By doing so, no noise is generated when the backlight is "on / off".

In each of the above embodiments, the case where liquid crystal is used as a display material is described as an example, but the present invention is not limited to this. For example, the present invention is applicable to any tablet device to which a display function using a display material for so-called non-light-emitting display such as electrochromism is added.

[0061]

As is apparent from the above description, the tablet device with the display function of the first invention has a display period and coordinate detection by the control means in the display-body tablet device in which the display function and the tablet function are integrally formed. Setting a period, and displaying an image on the display panel during the display period, and detecting the coordinates of the pointing device on the display panel during the coordinate detection period. In the above, the irradiation means for irradiating the display panel is turned on, while the voltage application means is controlled so that the irradiation means is not turned on in the coordinate detection period. Therefore, the irradiation means and the voltage application means in the coordinate detection period High-frequency electric field from the antenna can be eliminated. Therefore, according to the present invention, it is possible to eliminate a malfunction at the time of coordinate detection by eliminating an electrostatic noise caused by a high-frequency electric field from the light emitting source and the voltage applying means by the AC voltage during the coordinate detection period. Further, the control means
The AC voltage from the voltage application means to the irradiation means
For detecting coordinates after a predetermined time has elapsed since the application of
Starts electrode scanning, while electrode scanning for coordinate detection
After a predetermined time has passed since the end of
As described above, the application of the AC voltage to the irradiation means is started.
Since the voltage applying means is controlled, the voltage applying means
Timing of "ON / OFF" of AC voltage applied to launching means
Is set outside the electrode scanning period. So this
According to the present invention, the “on / off” of the AC voltage is
Even if it is performed near the peak of the pressure value, during the coordinate detection period
No electrostatic noise is generated, and malfunction during coordinate detection is more reliable
Can be prevented.

In the tablet device with a display function according to the second invention, the irradiation means for irradiating the display panel has a voltage application means.
Inducing the frequency of the AC voltage applied from the stage to the indicating means
Frequency that is different from the frequency band of the frequency component of the induced voltage
Since the wave number is set, the irradiation means and the voltage applying means
The static voltage superimposed on the above induced voltage by the high frequency electric field from
The electrical noise can be reliably separated from the frequency component of the above induced voltage.
You. Therefore, according to the present invention, during the coordinate detection period,
Source and its voltage applying means by AC voltage applied
Electrostatic noise caused by the high-frequency electric field of
Malfunction at the time of going out can be prevented.

Further, in the tablet device with a display function according to the third aspect of the present invention, the power supply is controlled by the application start / stop voltage control means.
Opening of the AC voltage applied from the pressure application means to the irradiation means
Control the start voltage and application stop voltage to be " 0 " volt
Noise occurs when turning on / off the irradiation means
do not do.

[Brief description of the drawings]

FIG. 1 is a block diagram of a backlight drive unit in a tablet device with a display function according to the present invention.

FIG. 2 is a block diagram of a backlight driver different from FIG.

FIG. 3 is a diagram showing backlight on / off timings in the backlight voltage application circuit shown in FIG. 1 or FIG. 2;

FIG. 4 is a diagram showing a supply voltage waveform when the backlight is turned on / off at the timing shown in FIG. 3;

FIG. 5 is a block diagram of an electrostatic induction tablet.

FIG. 6 is a block diagram of a display-integrated tablet device.

FIG. 7 is a diagram illustrating timings of a display period and a coordinate detection period in the display-integrated tablet device.

FIG. 8 is a cross-sectional view of the display-integrated tablet device.

[Explanation of symbols]

51: backlight; 52, 54: backlight voltage application circuit; 53, 55: power supply circuit.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G06F 3/033 350 G02F 1/133 530 G02F 1/133 535 G09G 3/36 H01H 36/00

Claims (3)

(57) [Claims] 1. A display panel having a first electrode group and a second electrode group arranged in different directions, respectively, and a position of the display panel which is electrostatically coupled to the first electrode group and the second electrode group. Instruction means for instructing the first electrode group, first driving means for driving the first electrode group, second driving means for driving the second electrode group,
Control for setting a display period for displaying on the display panel by controlling the first driving unit and the second driving unit and a coordinate detection period for performing coordinate detection based on an output signal guided by the instruction unit in a time-sharing manner. Means for illuminating the display panel by being lit by an AC voltage, and applying an AC voltage to the irradiating means. Voltage applying means for turning on the irradiating means, and the control means controls that the irradiating means is turned on during the display period, but is not turned on during the coordinate detection period, and From the voltage applying means
At a predetermined time after stopping the application of AC voltage to the irradiation means
After the passage of time, the electrode scanning for coordinate detection is started,
A predetermined time has passed since the end of electrode scanning for coordinate detection
Later, the AC voltage from the voltage applying means to the irradiation means
A tablet device with a display function , wherein the voltage application means is configured to be controllable so as to start application . 2. A tablet with a display function according to claim 1.
A display device, wherein the frequency of the AC voltage applied from the voltage applying means to the irradiation means is set to a frequency different from the frequency band of the frequency component of the induced voltage induced by the indicating means. With tablet device. 3. The tablet device with a display function according to claim 1 , wherein said voltage application is performed based on a control signal from said control means.
Start voltage of AC voltage applied from the means to the irradiation means
To control the voltage and the application stop voltage to be 0 volt
A tablet device with a display function, comprising a start / stop voltage control means .