JP4237741B2 - Liquid crystal display with touch panel - Google Patents

Description

  The present invention relates to a liquid crystal display device with a touch panel in which a transmissive touch panel is disposed on the screen side of a back illuminated liquid crystal display monitor having a backlight on the back side, and in addition to improving the transparency of the touch panel. The present invention relates to a technique for accurately obtaining the coordinates of a contact point of an object while simultaneously saving power of a liquid crystal display monitor and extending the life of a backlight.

Conventionally, as shown in FIGS. 10 and 11, a liquid crystal display with a touch panel in which a transparent touch panel 93 is provided on the screen side of a back illuminated liquid crystal display monitor 91 provided with a backlight 92 on the back side. The device is known.
There are various types of transmissive touch panels. The touch panel 93 is a capacitance (additional static electricity) added to the touch panel 93 that is generated when an object (such as a human finger or a pen) touches the touch panel 93. This is an analog capacitance type that obtains the coordinates of the contact point of the object on the touch panel 93 based on the change in the capacitance. In the case of the analog capacitive touch panel 93, a shield system is adopted in which an electrically shielding conductive film 94 is provided on the back side. The electric shield conductive film 94 prevents radiation noise from the liquid crystal display monitor 91 from entering the touch panel 93.

  The touch panel 93 sets the additional capacitance of the touch panel 93 when there is no object contact with the touch panel 93 as a reference capacitance value, and the additional capacitance generated by the contact of the object with the touch panel 93 is set to the reference capacitance value. When a threshold value that determines whether or not an object touches the touch panel 93 is added by adding a specific value that is less than the increment, and the additional capacitance of the touch panel 93 exceeds the threshold value, The coordinates of the contact point of the object are calculated based on the additional capacitance. Then, since the reference capacity value is obtained at a predetermined time interval and updated together with the threshold capacity value, the threshold capacity due to the change over time of the environment (for example, ambient temperature) in which the liquid crystal display device is placed. It is possible to prevent the malfunction by suppressing the fluctuation of the value (see, for example, Patent Document 1).

  On the other hand, the liquid crystal display monitor 91 is provided with a display drive circuit (not shown) and a signal processing circuit (not shown) for displaying an image in addition to the backlight 92, but the touch of the object on the touch panel 93 side. If there is no fixed period, the liquid crystal display monitor 91 side turns off the backlight 92 for back-lighting, the display drive circuit for image display, and the signal processing circuit. By turning it on again, power saving of the liquid crystal display monitor 91 and life extension of the backlight 92 are achieved.

Japanese Examined Patent Publication No. 6-12510 (pages 2 to 3, FIGS. 1 to 4).

  However, the conventional liquid crystal display device with a touch panel has a problem that the transparency of the touch panel 93 is insufficient. Even if the liquid crystal display monitor 91 is a back-illuminated type, the brightness of the screen tends to be insufficient compared to other monitors, and thus the transparency of the touch panel 93 is always required to be increased. However, as described above, in a conventional liquid crystal display device with a touch panel, it is practically necessary to reduce the power consumption of the liquid crystal display monitor and extend the life of the backlight. It must be determined accurately.

  The present invention has been made in view of such circumstances, and at the same time, coordinates of the contact point of an object while reducing power consumption of the liquid crystal display monitor and extending the life of the backlight in addition to improving the transparency of the touch panel. An object of the present invention is to provide a liquid crystal display device with a touch panel capable of accurately obtaining the above.

  The inventor first conducted intensive studies from various viewpoints, and paid attention to the fact that the transparency of the touch panel 93 can be easily improved by removing the conductive film 94 for the electric shield on the back side of the touch panel 93. The conductive film 94 for the electric shield uses a transparent conductive film with a light transmittance of over 80%, such as an ITO film. However, by removing this, the light transmittance of the touch panel 93 is increased to over 10%. Be made. However, since there is a concern about an increase in noise level when switching from the shield method to the shield dress method, the contact point of the object on the touch panel 93 is not changed in the process of careful consideration except for the conductive film 94 for the electric shield. It has been found that sometimes the coordinates are not calculated correctly.

  On the other hand, in the case of a liquid crystal display device with a touch panel that the inventor considered this time, the additional capacitance of the touch panel that slowly changes due to an environmental change (for example, a change in ambient temperature) is detected. In addition to setting the additional capacitance as a reference capacitance value and determining the presence or absence of an object touching the touch panel, in addition to setting a first threshold capacitance value determined with reference to the reference capacitance value, In order to determine whether or not there is an object approaching, a second threshold capacitance value that is determined based on the reference capacitance value and is smaller than the first threshold capacitance value is set.

  Then, when the additional capacitance of the touch panel exceeds the first threshold capacitance value, the coordinates of the contact point of the object are calculated based on the additional capacitance of the touch panel. However, when the additional capacitance of the touch panel is less than the first threshold capacitance value and greater than or equal to the second threshold capacitance value for a predetermined period of time, it is determined that there is an object approaching and that there is an object approaching. In this case, the coordinates of the contact point of the object are corrected in consideration of the capacity increase accompanying the approach of the object.

  A typical example of the approach of an object is a state where the user of the touch panel holds the left palm close to the touch panel. When the user's palm is held over the touch panel, the additional capacitance increases. In this state, when the user touches the touch panel with the right finger and the additional capacitance exceeds the first threshold capacitance value. The coordinates of the contact point of the object are calculated, but the increase in the additional capacitance due to the approach of the palm is not due to the touch of the finger, so the increase in the additional capacitance due to the approach of the palm as it is Calculation error is introduced. Therefore, when it is determined that the object is approaching due to the palm being held over, etc., the contact due to the approach of the object is corrected by correcting the coordinates of the contact point of the object in consideration of the increase in capacity accompanying the approach of the object by weighting processing etc. The calculation error of the coordinates of the point is avoided.

  On the other hand, in the case of the liquid crystal display device with a touch panel that the inventor considered this time, if there is no object contact on the touch panel side for a predetermined time, the power save mode is executed on the liquid crystal display monitor side to The display drive circuit (display drive means) and the signal processing circuit (signal processing means) for displaying the backlight and the image display are all turned off, and the power save mode is stopped again when the object touches the touch panel. By turning everything on, the power consumption of the liquid crystal display monitor and the life of the backlight are extended.

  Then, the inventor continued to observe and analyze the calculation operation of the coordinates of the contact point of the object in order to investigate the reason why the coordinates of the contact point of the object on the touch panel are sometimes not correctly calculated. As a result, it was found that the following phenomenon occurred. While the power save mode is running, the radiant noise of the LCD monitor that causes an apparent increase in the additional capacitance of the touch panel disappears, so the increase in additional capacitance due to the radiated noise is removed and the reference capacitance value becomes At the same time, the second threshold capacity value decreases as the reference capacity value decreases.

  When the power saving mode is shifted to a state where the second threshold capacitance value is lowered, an increase in additional capacitance due to radiation noise of the liquid crystal display monitor appears again. However, the reference capacity value does not increase immediately with the stop of the power save mode. For example, if the reference capacity value is updated every 30 seconds, a time delay of at least 30 seconds occurs before the reference capacity value increases. When the rise of the reference capacitance value is delayed, the rise of the second threshold capacitance value set based on this is also delayed. As a result, the additional capacitance of the touch panel is often greater than or equal to the second threshold capacitance value even when no object is approaching. Even when the object is not approaching, it is determined that the object is approaching when the additional capacitance of the touch panel is equal to or greater than the second threshold capacitance value for a predetermined period of time. That is, a pseudo approach phenomenon of an object occurs. Furthermore, the object touches and the touch panel additional capacitance exceeds the first threshold capacitance value while the pseudo approach phenomenon of the object continues and the touch panel additional capacitance exceeds the second threshold capacitance value. Then, the coordinates of the contact point of the object are corrected in consideration of the increase in capacity accompanying the approach of the object even though the object is not actually approaching.

  That is, the inventor found that the additional capacitance of the touch panel was increased by the increase in the apparent additional capacitance due to the provision of radiation noise of the liquid crystal display monitor when the power save mode was stopped, even though no object was approaching. However, the fact that the second threshold capacity value, which has decreased due to the decrease in the reference capacity value with the execution of the power save mode, is the cause of the calculation error of the coordinates of the contact point of the object on the touch panel. I was able to get.

Subsequently, the inventor continued further investigation according to the knowledge thus obtained, turned off only the backlight for backlighting, and turned on the display drive circuit and the signal processing circuit for image display. If the power save mode is executed without any change, the reference capacity value and the second threshold capacity value will not drop significantly as the power save mode is executed. The knowledge that it was possible to avoid the situation where the additional capacitance of the touch panel exceeded the second threshold capacitance value by providing radiation noise of the liquid crystal display monitor when the mode was stopped was obtained. In addition, the power consumption of the backlight is greater than the power consumption of the display drive circuit and signal processing circuit for image display, so even when the backlight is turned off, the power consumption of the LCD monitor can be sufficiently reduced. I was able to confirm that
In other words, the inventor has finally reached the completion of the invention by acquiring the knowledge necessary for the completion of the invention as described above.

Therefore, in order to achieve the above object, the following configuration is adopted.
That is, according to the first aspect of the present invention, a transmissive touch panel is disposed on the screen side of the liquid crystal display monitor, and the liquid crystal display monitor is a back-illuminated type having a backlight on the back side. in the four corners of the transparent conductive film provided on the touch panel, the touch panel that are added to the capacitance (additional capacitance) is measured, the measured added static caused by the contact of an object on the touch panel A liquid crystal display device with a touch panel that is an analog capacitive type that obtains coordinates of a contact point of an object on a touch panel based on a change in electric capacity , and the liquid crystal display monitor includes display drive means for displaying an image And the signal processing means are attached, and the touch panel is a touch panel not provided with a conductive film for electrical shielding, and is caused by an environmental change. A reference capacitance value setting unit that detects the additional capacitance of the touch panel that has changed slowly and sets the additional capacitance as a reference capacitance value, and a reference capacitance to determine whether an object touches the touch panel. A first threshold capacitance value setting means for setting a first threshold capacitance value determined on the basis of the value, and a reference capacitance value for determining whether or not an object approaches the touch panel; Second threshold capacitance value setting means for setting a second threshold capacitance value smaller than the threshold capacitance value, and a state in which the additional capacitance of the touch panel is less than the first threshold capacitance value and greater than or equal to the second threshold capacitance value but the object proximity determining means for determining that there is an object approaching when lasted a certain time determined in advance, the additional capacitance of the touch panel of the touch panel when it exceeds the first threshold capacitance value, four with the which is the measuring Calculates coordinates of the contact point of the object based on capacitance, further, if it is determined that there is an object approaching the object proximity determination unit, due to the object proximity, increasing the capacity of four additional capacitance which is the measuring Contact point coordinate calculation means for correcting the coordinates of the contact point of the object so as to eliminate the coordinate calculation error caused by
When there is no contact of the object with the touch panel for a predetermined time, the display driving means and the signal processing means attached to the liquid crystal display monitor remain in the operating state, and only the backlight is shifted to the off state. And a power saving control unit that shifts the backlight to an on state in accordance with the contact of the object.

  [Operation / Effect] In the liquid crystal display device with a touch panel according to the first aspect of the present invention, the analog capacitive touch panel disposed on the screen side of the liquid crystal display monitor has a conductive film for electrical shielding. Since it is a shieldless system that does not have, the transparency of the touch panel is improved by an amount corresponding to the light shielding rate of the electric shielding conductive film.

  Further, as the operation of the liquid crystal display device with a touch panel according to the first aspect of the invention is started, the reference capacitance value setting means, on the touch panel side, increases the additional capacitance of the touch panel that slowly changes due to environmental changes. The additional capacitance is detected and set as a reference capacitance value. Further, the first threshold capacitance value setting means sets a first threshold capacitance value determined with reference to the reference capacitance value in order to determine whether or not an object touches the touch panel, and the second threshold capacitance value. The setting means sets a second threshold capacitance value that is determined based on the reference capacitance value and is smaller than the first threshold capacitance value in order to determine whether or not an object is approaching the touch panel. As a result, both the reference capacitance value and the first and second threshold capacitance values are appropriate capacitance values reflecting changes with time of the environment such as the ambient temperature of the touch panel. The contact point coordinate calculating means calculates the coordinates of the contact point of the object based on the additional capacitance of the touch panel when the additional capacitance of the touch panel exceeds the first threshold capacitance value, and further, by the object approach determining means When it is determined that an object is approaching, the coordinates of the contact point of the object are corrected in consideration of the amount of change in additional capacitance accompanying the approach of the object.

  During operation of the liquid crystal display device with a touch panel according to the first aspect of the present invention, if the object does not touch the touch panel side for a predetermined time, the power saving control means includes display driving means and signal processing means attached to the liquid crystal display monitor. Only the backlight is shifted to the off state while the operation state is maintained. The additional capacitance of the touch panel is reduced only by the radiation noise due to the backlight being turned off, and the reference capacitance value and the second threshold capacitance value are not significantly reduced.

  In addition, when the backlight is turned on when an object touches the touch panel, the additional capacitance of the touch panel is increased only by the radiation noise due to the turning on of the backlight, and the additional capacitance of the touch panel is the second. It does not exceed the threshold capacity value. Therefore, an error in calculating the coordinates of the contact point of an object may be caused by mistakenly considering the increase in the apparent capacitance due to the provision of radiation noise when the backlight is turned on as an increase in the capacitance due to the approach of the object. In addition, the coordinates of the contact point of the object on the touch panel are accurately calculated.

  In addition, the power consumption of the backlight of the liquid crystal display monitor is greater than the power consumption of the display driving means and the signal processing means for image display. Thus, the power of the liquid crystal display monitor can be saved by turning off the backlight when there is no object contact for a predetermined time.

  In the liquid crystal display device with a touch panel according to the present invention, the analog capacitive touch panel disposed on the screen side of the liquid crystal display monitor is a shieldless system that does not have a conductive film for electrical shielding. The transmittance of the touch panel is improved by an amount corresponding to the light shielding rate of the electrically shielding conductive film.

  In the case of the liquid crystal display device with a touch panel according to the present invention, the additional capacitance of the touch panel that changes slowly due to environmental changes is detected, and the additional capacitance is detected based on the presence or absence of object contact with the touch panel and the proximity of the object. Since the first and second threshold capacitance values that are the threshold capacitance values for determining the presence or absence of the threshold value are set as the reference capacitance values, the first and second thresholds are set in addition to the reference capacitance values. The capacitance value also becomes an appropriate capacitance value that reflects the change over time of the environment such as the ambient temperature of the touch panel.

  In addition, during operation of the liquid crystal display device with a touch panel of the present invention, when there is no contact with an object on the touch panel side for a predetermined time, only the backlight is turned off, and the additional capacitance of the touch panel is a component of radiation noise caused by turning off the backlight. The backlight is turned on when the object touches the touch panel, and the additional capacitance of the touch panel increases only by the radiation noise caused by turning on the backlight. In addition, the additional capacitance of the touch panel does not exceed the second threshold capacitance value when the additional capacitance of the touch panel returns to the ON state of the backlight. As a result, the coordinates of the contact point of the object on the touch panel are calculated by mistaking the slight increase in the apparent capacitance due to the radiation noise caused by turning on the backlight as the increase in the capacitance due to the approach of the object. No mistakes are made.

  As described above, the first and second threshold capacitance values, which are threshold capacitance values for determining whether or not an object touches the touch panel and whether or not an object approaches, reflect changes in the environment such as the ambient temperature of the touch panel. In addition, the coordinates of the contact point of the object are mistakenly considered as an increase in the capacitance due to the approach of the object. Since the calculation error does not occur, the coordinates of the contact point of the object on the touch panel can be obtained accurately.

  In addition, in the case of the liquid crystal display device with a touch panel according to the present invention, the power consumption of the backlight of the liquid crystal display monitor is greater than the power consumption of the display driving means and the signal processing means for image display. During the operation of the attached liquid crystal display device, the power of the liquid crystal display monitor can be saved by turning off the backlight when there is no contact of an object on the touch panel side for a predetermined time.

  Therefore, according to the liquid crystal display device with a touch panel of the present invention, in addition to improving the transparency of the touch panel, the power consumption of the liquid crystal display monitor (power saving) and the life extension of the backlight are achieved, and at the same time, The coordinates can be obtained accurately.

  An embodiment of a liquid crystal display device with a touch panel according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an interactive computer application system using a liquid crystal display device with a touch panel of the embodiment (hereinafter abbreviated as “liquid crystal display device” as appropriate) as an input / output tool, and FIG. FIG. 3 is a block diagram showing a liquid crystal display monitor and a monitor control drive unit of the apparatus of the embodiment, and FIG. 4 is a touch panel, a liquid crystal display monitor and a panel of the apparatus of the embodiment. It is a block diagram which shows the detection calculating part.

  The interactive computer application system of FIG. 1 is provided with a liquid crystal display device 1 of an embodiment that is an input / output tool and a personal computer PC that is a host computer. The liquid crystal display device 1 includes a back illuminated liquid crystal display monitor 2 having a backlight 3 on the back side, a monitor control drive unit 4 for executing control drive processing necessary for image display by the liquid crystal display monitor 2, and a liquid crystal display. A transparent touch panel 5 disposed on the screen side of the display monitor 2 and a panel detection calculation unit 6 that executes detection calculation processing necessary for calculating the coordinates of the contact point of the object on the touch panel 5 are provided. Yes.

  In the interactive computer application system of FIG. 1, for example, when an appropriate operation menu image is displayed on the screen 2A of the liquid crystal display monitor 2 in accordance with the control of the personal computer PC, the image is output to the screen 2A of the liquid crystal display monitor 2. An input is performed on the touch panel 5 while viewing the image. That is, the user of the system touches (touches) a desired position on the operation menu image on the screen 2A of the liquid crystal display monitor 2 that can be seen through the touch panel 5 with a finger (object). Then, the panel detection calculation unit 6 immediately calculates (two-dimensional) coordinates of the contact point of the finger on the touch panel 5 and sends it to the personal computer PC.

  The personal computer PC sends a command corresponding to the coordinate of the contact point of the finger on the touch panel 5 received from the panel detection calculation unit 6 to the monitor control drive unit 4. The monitor control drive unit 4 immediately performs a change process on the image corresponding to the command received from the personal computer PC. As a specific example of the change process for the image, there is a process for changing the display color of the position corresponding to the contact position of the finger in the image.

  Hereinafter, the liquid crystal display device of the embodiment which is an input / output tool of the interactive computer application system of FIG. 1 will be described in detail.

  In the liquid crystal display monitor 2, as shown in FIG. 2, the backlight 3 emits illumination light L from the back side to make the screen 2A of the liquid crystal display monitor 2 bright and easy to see. In the case of the embodiment, since the backlight 3 is a planar light emitter, the illumination of the backlight 3 is uniform and uniform.

  As shown in FIG. 3, the monitor control drive unit 4 includes a display drive circuit 7 for displaying an image, a signal processing circuit 8, and a drive power supply unit 9. The drive power supply unit 9 has a voltage of 5V (volts). Driving power is supplied to the display driving circuit 7, and driving power having a voltage of 15 V (volt) is supplied to the backlight 3 via the inverter circuit 10. The signal processing circuit 8 includes a video processing circuit 8A and a synchronization processing circuit 8B for processing a video signal and a synchronization signal received from the personal computer PC, respectively. Further, the monitor control drive unit 4 has a sub-computer CPU1, and the sub-computer CPU1 controls the display drive circuit 7 to the inverter circuit 10 in accordance with a control command received from the personal computer PC. Appropriate images are displayed on the screen 2A of the liquid crystal display monitor 2 and power saving control is performed.

  The touch panel 5 determines the contact point of an object on the touch panel 5 based on a change in capacitance (additional capacitance) added to the touch panel 5 caused by a finger or pen (object) touching the touch panel 5. In addition to the analog capacitance type for obtaining coordinates, the shieldless method is not provided with a conductive film for electrical shielding. In the case of the touch panel 5, as shown in FIG. 2, a transparent conductive film 12 for contact position sensing is provided on the surface of a highly permeable insulating base material 11 made of glass or the like and covered with a permeable protective film 13. Yes. For example, an ITO film is used as the transparent conductive film 12, and the entire shape of the transparent conductive film 12 is a square.

  As shown in FIG. 4, the panel detection calculation unit 6 includes four capacitance detection units 14 that measure the additional capacitance of the touch panel 5 at four corners of the transparent conductive film 12. The electrostatic capacitance detection unit 14 includes, for example, a common high-frequency oscillation unit 15 that outputs a high-frequency voltage having a frequency of 50 kHz to 110 kHz, and a minute high-frequency current corresponding to the capacitance between the four corners of the transparent conductive film 12 and the ground. Is converted into a voltage as an additional capacitance of the touch panel 5 and output. Further, the panel detection calculation unit 6 has a sub-computer CPU 2, and calculates the coordinates of the contact point on the touch panel 5 according to the voltage as the additional capacitance received from each current-voltage conversion unit 16 by the sub-computer CPU 2. To do. Specifically, the coordinates of the contact point are calculated based on the capacitance difference between the four additional capacitances generated according to the position of the contact point.

  Further, the sub-computer CPU2 of the embodiment has the following functions in order to accurately calculate the coordinates of the contact point on the touch panel 5. That is, the sub computer CPU2 detects the additional capacitance of the touch panel 5 that has changed slowly due to environmental changes (for example, changes in ambient temperature), and sets the additional capacitance as a reference capacitance value. In order to determine whether or not an object touches the touch panel 5, a first threshold capacity value determined based on the reference capacity value is set, and in addition, a reference is used to determine whether or not an object approaches the touch panel. A second threshold capacitance value that is determined based on the capacitance value and is smaller than the first threshold capacitance value is set.

  Specifically, as shown in FIG. 5, the sub-computer CPU2 checks that the additional capacitance CH of the touch panel 5 is less than a predetermined capacitance value determined in advance at predetermined time intervals, and checks the added static capacitance. A reference capacitance value setting function for setting the capacitance CH as a reference capacitance value CH0, and a first specific value H1 that exceeds the minimum increase amount of the additional capacitance CH generated by contact of an object with the touch panel 5 on the reference capacitance value CH0. A first threshold capacitance value setting function that is set as a first threshold capacitance value CH1 for determining whether or not an object touches the touch panel 5 is added, and an approach of the object to the touch panel 5 is assumed based on the reference capacitance value. A second threshold capacitance value CH2 that determines whether or not an object has approached the touch panel 5 by adding a second specific value H2 that is smaller than the maximum increase in the additional capacitance CH and is smaller than the first specific value H1. To and a second threshold capacitance value setting function of setting.

Further, the sub-computer CPU2 calculates the coordinates of the contact point of the object based on the additional capacitance CH of the touch panel 5 when the additional capacitance CH of the touch panel 5 exceeds the first threshold capacitance value CH1. When the calculation function and the state where the additional capacitance CH of the touch panel 5 is less than the first threshold capacitance value CH1 and greater than or equal to the second threshold capacitance value CH2 continue for a predetermined time (for example, 1 second), the object approaches It has an object approach discrimination function that discriminates the presence. Note that the predetermined capacity value that is set in advance when the additional capacitance CH of the touch panel 5 is checked by the reference capacity value setting function is within the range of the second threshold capacity value CH2 that is currently set. It is assumed that the predetermined capacity value is just set to the second threshold capacity value CH2.
Further, in the sub computer CPU2, when it is determined that the object is approaching by the object approach determining function, the coordinate of the contact point of the object is corrected and calculated by taking into account the increase in capacity accompanying the approach of the object by the contact point coordinate calculating function. ing.

  On the other hand, on the liquid crystal display monitor 2 side, if there is no object contact on the touch panel 5 side for a predetermined time (because there is no system user), a power save command is sent from the personal computer PC to the monitor control drive unit 4. To do. Based on the power save command received from the personal computer PC, the monitor control drive unit 4 immediately turns off only the backlight 3 and keeps the display drive circuit 7 and the signal processing circuit 8 on. In addition, a power save stop command is sent from the personal computer PC to the monitor control drive unit 4 as the object touches the touch panel 5, and the backlight 3 is turned on again.

Next, the coordinate calculation process of the contact point on the touch panel 5 of the liquid crystal display device with a touch panel according to the embodiment described above will be described with reference to the drawings. FIG. 6 is a graph showing the change with time of the capacitance factor of the touch panel 5 of the embodiment device, and FIG. 7 is a flowchart showing the coordinate calculation process of the contact point of the touch panel 5.
In the following, it is assumed that the liquid crystal display monitor 2 is in operation and the backlight 3 is in an on state, and the reference capacity value CH0 and the first threshold capacity of the touch panel 5 are set according to the setting functions exhibited by the subcomputer CPU2. In parallel with the setting of the value CH1 and the second threshold capacitance value CH2, the coordinate calculation process of the touch point of the touch panel 5 proceeds.

  [Step S1] The additional capacitance CH of the touch panel 5 is acquired one after another.

  [Step S2] If the acquired additional capacitance CH of the touch panel 5 is less than the second threshold capacitance value CH2, the process returns to step S1, and if the second threshold capacitance value CH2 is greater than or equal to the above, the process proceeds to step S3.

  [Step S3] If the additional capacitance CH of the touch panel 5 is longer than the second threshold capacitance value CH2 for less than 1 second (assuming that there is a possibility of object contact), the process proceeds to Step S4. If it is more than 2 seconds (assuming that the object is approaching), the process proceeds to step S5.

  [Step S4] If the additional capacitance CH of the touch panel 5 is equal to or greater than the first threshold capacitance value CH1, as indicated by a peak P1 in the curve indicating the additional capacitance CH in FIG. The coordinate calculation function calculates the coordinates of the contact point of the object without taking into account the increase in capacity due to the approach of the object (S4A), and if it is less than the first threshold capacity value CH1 (considered as a capacity fluctuation due to temporary noise). The coordinates of the contact point of the object are not calculated, and the process returns to step S1.

  [Step S5] If the additional capacitance CH of the touch panel 5 is equal to or greater than the first threshold capacitance value CH1, as indicated by a peak P2 in the curve indicating the additional capacitance CH in FIG. The coordinate calculation function corrects and calculates the coordinates of the contact point of the object taking into account (weighting) the increase in capacity accompanying the approach of the object (S5A), and if it is less than the first threshold capacity value CH1, the process proceeds to step S6.

  [Step S6] If the additional capacitance CH of the touch panel 5 is greater than or equal to the second threshold capacitance value CH2, the process returns to step S5, and if it is less than the second threshold capacitance value CH1, the process returns to step S1.

  The setting of the reference capacitance value CH0 of the touch panel 5 is a slow change such that the additional capacitance CH of the touch panel 5 acquired one after another is less than the second threshold capacitance value CH2 for 30 seconds. A suitable additional capacitance (for example, an average value) in the meantime is replaced with a reference capacitance value CH0 so far as a new reference capacitance value CH0. It goes without saying that the first threshold capacitance value CH1 and the second threshold capacitance value CH2 are also updated with the update of the reference capacitance value CH0. When the additional capacitance CH of the touch panel 5 becomes equal to or greater than the second threshold capacitance value CH2, the sub computer CPU2 stops the reference capacitance value setting function.

  Therefore, in the case of the apparatus according to the embodiment, it is checked that the additional capacitance CH of the touch panel 5 is equal to or smaller than a predetermined capacitance value determined in advance at predetermined time intervals, and the checked additional capacitance CH is transferred to the touch panel 5. Since the first and second threshold capacitance values CH1 and CH2 that are threshold capacitance values for determining whether or not an object is touching and whether or not an object is approaching are set as a reference capacitance value CH0, the reference capacitance value is set. In addition to CH0, the first and second threshold capacitance values CH1 and CH2 are also appropriate capacitance values reflecting changes with time of the environment such as the ambient temperature of the touch panel 5.

On the other hand, if there is no object contact on the touch panel 5 side for a predetermined time, only the backlight 3 is turned off according to the power save command issued from the personal computer PC.
While the power is being saved, the reference capacitance value CH0 of the touch panel 5 is continuously updated. As the backlight 3 is turned off as shown in FIG. Since the radiation noise is reduced by the off state, the reference capacitance value CH0 of the touch panel 5 becomes slightly lower with a slight delay.

  When an object is touched on the touch panel 5 side, only the backlight 3 is turned on in accordance with the power save stop command issued from the personal computer PC, so that the additional capacitance CH of the touch panel 5 is the backlight 3. Therefore, the reference capacitance value CH0 of the touch panel 5 becomes slightly higher with a slight delay.

  On the other hand, in the conventional apparatus, the display drive circuit 7 and the signal processing circuit 8 are also turned off in addition to the backlight 3 during power saving, so that the display drive circuit 7 and the signal processing of the backlight 3 as shown in FIG. Since the additional capacitance CH of the touch panel 5 is reduced by the total amount of radiation noise caused by the circuit 8 being turned off, the reference capacitance value CH0 and the second threshold capacitance value CH2 of the touch panel 5 are greatly reduced. When the power saving is stopped, the display driving circuit 7 and the signal processing circuit 8 are simultaneously turned on in addition to the backlight 3, so that the total amount of radiation noise due to the turning off of the display driving circuit 7 and the signal processing circuit 8 of the backlight 3. The additional capacitance CH of the touch panel 5 immediately increases, but the reference capacitance value CH0 of the touch panel 5 does not increase immediately.

  As a result, in the case of the conventional apparatus, the additional capacitance CH of the touch panel 5 is equal to or greater than the second threshold capacitance value CH2 even when no object is approached, and if it is equal to or greater than the second threshold capacitance value CH2. If there is an object touching the touch panel 5 again during ta, there is no object approaching the touch panel 5 and the increase in capacity accompanying the object approach should not be taken into account. Since the coordinates of the contact point of the object are calculated in consideration of the capacity increase accompanying the approach of the object, an error occurs in the calculated result.

  However, in the case of the apparatus of the embodiment, as described above, only the backlight 3 is turned off during power saving, and the degree of decrease in the additional capacitance CH of the touch panel 5 is small. 2 The threshold capacitance value CH2 does not decrease greatly. Further, since the backlight 3 is only turned back on when the power saving is stopped, the additional capacitance CH of the touch panel 5 is only slightly increased by the amount of radiation noise caused by the backlight 3 being turned on.

  Therefore, in the apparatus of the embodiment, when the power saving is stopped, the second threshold capacitance value CH2 is not greatly decreased, and the additional capacitance CH of the touch panel 5 is not significantly increased. Although the additional capacitance CH of the touch panel 5 is not approached by an object, it does not exceed the second threshold capacitance value CH2. As a result, in the apparatus of the embodiment, there is a disadvantage that the coordinates of the contact point of the object are calculated in consideration of the capacity increase accompanying the approach of the object by the contact point coordinate calculation function even though the object is not actually approaching. Never happen.

In the apparatus of the embodiment described above, since the touch panel 5 is of the shieldless system, the transparency of the touch panel 5 is improved by the light shielding rate of the electrically shielding conductive film.
In addition, in the case of the apparatus according to the embodiment, the first and second threshold capacitance values CH1 and CH2 that are threshold capacitance values for determining whether or not an object touches the touch panel 5 and whether or not an object approaches the touch panel 5 are the surroundings of the touch panel 5. In addition to an appropriate capacitance value that reflects temporal changes in the environment such as temperature, a slight increase in the apparent capacitance due to the provision of radiation noise that accompanies the turning on of the backlight 3 reduces the capacitance due to the approach of the object. Since there is no mistake in calculating the coordinates of the contact point of the object by mistakenly considering it as an increase, the coordinates of the contact point of the object on the touch panel 5 can be accurately obtained.

In addition, since the power consumption of the backlight 3 of the liquid crystal display monitor 2 is greater in weight than the power consumption of the display driving circuit 7 and the signal processing circuit 8 for image display, the apparatus of the embodiment operates the apparatus. In the middle, when the touch panel 5 does not contact the object for a certain period, the backlight 3 is turned off, so that the power consumption of the liquid crystal display monitor can be reduced.
Therefore, according to the liquid crystal display device with a touch panel of the embodiment, the coordinates of the contact point of the object are simultaneously achieved while saving the power of the liquid crystal display monitor 2 and extending the life of the backlight 3 in addition to improving the transparency of the touch panel 5. Can be obtained accurately.

The present invention is not limited to the above embodiment, and can be modified as follows.
(1) In the liquid crystal display device with a touch panel of the present invention, the detection method of the additional capacitance of the touch panel 5 is not limited to the configuration shown in FIG.

  (2) The liquid crystal display device with a touch panel of the present invention may be used other than an input / output tool of a computer application system.

It is a block diagram which shows the outline | summary structure of the interactive computer application system which used the liquid crystal display device with a touch panel of an Example for the input / output tool. It is a side view which shows the principal part of an Example apparatus. It is a block diagram which shows the liquid crystal display monitor and monitor control drive part of an Example apparatus. It is a block diagram which shows the touchscreen of the Example apparatus, a liquid crystal display monitor, and the detection calculating part for panels. It is a graph which shows the relationship between the capacitance factors of the touch panel of an Example apparatus. It is a graph which shows the time-dependent change of the electrostatic capacitance factor of the touch panel of an Example apparatus. It is a flowchart which shows the coordinate calculation process of the contact point of the touch panel in an Example apparatus. It is a graph which shows the time-dependent change of the electrostatic capacitance factor of a touch panel in the period which pinches | interposes the power save mode execution time of an Example apparatus. It is a graph which shows the time-dependent change of the electrostatic capacitance factor of the touch panel in the period which pinches | interposes the power save mode execution time of a conventional apparatus. It is a side view which shows the principal part of the conventional apparatus. It is a perspective view which shows the principal part of the conventional apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device with a touch panel 2 ... Liquid crystal display monitor 3 ... Backlight 4 ... Monitor control drive part 5 ... Touch panel 6 ... Panel detection calculation part 7 ... Display drive circuit (display drive means)
8: Signal processing circuit (signal processing means)
CH… Additional capacitance CH0… Reference capacitance value CH1… First threshold capacitance value CH2… Second threshold capacitance value

Claims (1)

A transmissive touch panel is disposed on the screen side of the liquid crystal display monitor, the liquid crystal display monitor is a back-illuminated type with a backlight on the back side, and the touch panel is a transparent conductive film 4 provided on the touch panel. At each corner, the capacitance (additional capacitance) added to the touch panel is measured, and based on the change in the measured additional capacitance that occurs as the object touches the touch panel, A liquid crystal display device with a touch panel, which is an analog capacitive type for obtaining coordinates of a contact point,
The liquid crystal display monitor is provided with display driving means and signal processing means for image display,
The touch panel is a touch panel that is not provided with a conductive film for electrical shielding,
A reference capacitance value setting means for detecting an additional capacitance of the touch panel that slowly changes due to an environmental change and setting the additional capacitance as a reference capacitance value;
First threshold capacitance value setting means for setting a first threshold capacitance value determined on the basis of the reference capacitance value in order to determine whether or not an object touches the touch panel;
Second threshold capacity value setting means for setting a second threshold capacity value that is determined based on a reference capacity value and is smaller than the first threshold capacity value in order to determine whether or not an object has approached the touch panel;
An object approach determining means for determining that an object is approaching when a state where the additional capacitance of the touch panel is less than the first threshold capacitance value and greater than or equal to the second threshold capacitance value continues for a predetermined period of time;
When the additional capacitance of the touch panel exceeds the first threshold capacitance value, the coordinates of the contact point of the object are calculated based on the measured four additional capacitances of the touch panel, and further, the object approach discrimination means When it is determined that there is an object approaching, contact point coordinates for correcting the coordinates of the contact point of the object so as to eliminate the calculation error of the coordinates caused by the increase in capacity of the four measured additional capacitances accompanying the object approaching A calculation means;
When there is no contact of the object with the touch panel for a predetermined time, the display driving means and the signal processing means attached to the liquid crystal display monitor remain in the operating state, and only the backlight is shifted to the off state. A liquid crystal display device with a touch panel, comprising: a power saving control unit that shifts the backlight to an on state in accordance with contact of an object.

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