JP2012083592A - Display device incorporating optical sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device incorporating an optical sensor that has improved detection sensitivity with a configuration in which the light incident to the optical sensor is only from a light source for the optical sensor.SOLUTION: The display device incorporating the optical sensor has a display panel with a plurality of pixels, at least one of the pixels having an optical sensor. The device includes a light source for visible light, for emitting visible light, and a light source for invisible light, for emitting invisible light. One frame period is composed of an image display period and a touch-position detecting period. An image is displayed on the display panel by turning off the light source for invisible light and turning on the light source for visible light during the image display period. A place on the display panel, which place has been touched by an observer, is detected by the optical sensor by turning off the light source for visible light and turning on the light source for invisible light during the touch-position detecting period.

Description

  The present invention relates to a display device with a built-in optical sensor, and in particular, light that uses a light source that emits light of a wavelength other than the visibility (for example, a light source for invisible light such as infrared rays or ultraviolet rays) as a light source for optical sensors. The present invention relates to a sensor built-in display device.

At present, products having various high-value-added functions are put into practical use in mobile phones that use a liquid crystal display panel as a display unit, and an optical sensor built in the liquid crystal display panel is one of them. (See Patent Document 1 below)
As an application of the light sensor in the mobile phone, an external light sensor detects ambient brightness and automatically adjusts the brightness of the backlight. There are a wide variety of uses such as detecting the touched position.

JP 2008-300530 A

A problem with a touch panel using an optical sensor built in a liquid crystal display panel is identifying a regular touch input and a noise input due to external light with high accuracy. For example, when the reflected light of the backlight light of the liquid crystal display device is captured by the sensor built in the liquid crystal display panel as reflected light from the observer's finger touching the liquid crystal display panel, the touch may occur depending on the usage environment. There may be a case where it is not possible to distinguish between reflected light from the finger and external light (post-detection).
In order to increase the reliability of the identification, a method of intentionally changing the brightness of the backlight and adding information on the intensity of the backlight has been proposed, but at the same time, it is necessary to consider the influence on the display image quality.
In order to avoid this, a light source that emits light of a wavelength other than the visibility (for example, a light source for invisible light such as infrared rays or ultraviolet rays) is used as the light source for the optical sensor, and the brightness is intentionally set. There has also been proposed a method of changing and adding information of the strength.
However, the reflected light incident on the optical sensor also includes light from the backlight, and thus there is a problem that it is necessary to adjust the sensitivity of the optical sensor to the light emitted from the light source for the optical sensor. It was.
The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide light with only a light source for an optical sensor as input light to the optical sensor and improved detection sensitivity. The object is to provide a sensor built-in display device.
The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
(1) A display panel having a plurality of pixels, wherein at least one of the plurality of pixels is a photosensor built-in display device having a photosensor, and a visible light source that emits visible light; A light source for invisible light that emits invisible light, and one frame period includes an image display period and a touch position detection period, and the high light source for invisible light is turned off within the image display period, The visible light source is turned on, an image is displayed on the display panel, the visible light source is turned off, the invisible light source is turned on, and the light sensor is turned on the display panel within the touch position detection period. The touch position of the observer is detected.
(2) In (1), the visible light source is a first light source that emits light of a first color, a second light source that emits light of a second color, and light of a third color. A third light source for irradiating, and in the image display period, the second light source and the third light source are turned off, and the first light source is turned on, and a first color image is displayed on the display panel. A first image display period; a second image display period in which the first light source and the third light source are turned off; the second light source is turned on; and a second color image is displayed on the display panel; The first light source and the second light source are turned off, the third light source is turned on, and a third image display period in which an image of the third color is displayed on the display panel.
(3) In (1) or (2), the display panel is configured such that invisible light from the invisible light source is incident on the photosensor from a surface of the liquid crystal display panel opposite to the observer. It has a light shielding film to prevent.
(4) In any one of (1) to (3), the display panel is a liquid crystal display panel having a backlight, and the visible light source and the invisible light source are included in the backlight. Be placed.
(5) In (4), the backlight has a light guide plate, and the light source for visible light and the light source for invisible light are arranged on at least one side surface of the light guide plate.
(6) In any one of (1) to (5), the optical sensor is formed of a photodiode.

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
According to the photosensor inner layer display device of the present invention, the input light to the photosensor is made only of the photosensor light source, and the detection sensitivity can be improved.

It is a disassembled perspective view which shows schematic structure of the conventional liquid crystal display device. It is a circuit diagram which shows the equivalent circuit of the liquid crystal display panel with a built-in photosensor in which the photosensor was incorporated in 1 pixel used as the premise of this invention. FIG. 3 is a schematic cross-sectional view showing a cross-sectional structure of one pixel in which the photosensor shown in FIG. 2 is incorporated. It is a circuit diagram which shows the equivalent circuit of the liquid crystal display panel which has arrange | positioned the pixel incorporating an optical sensor in the array form. FIG. 5 is a circuit diagram illustrating the optical sensor unit and the readout circuit unit illustrated in FIG. FIG. 6 is a timing chart for explaining the operation of the circuit shown in FIG. 5. It is sectional drawing which shows the actual sectional structure of 1 pixel incorporating the optical sensor shown in FIG. It is a timing chart for demonstrating the drive method of the liquid crystal display panel with an optical sensor of Example 1 of this invention. It is a timing chart for demonstrating the drive method of the liquid crystal display panel with an optical sensor of Example 2 of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In all the drawings for explaining the embodiments, parts having the same functions are given the same reference numerals, and repeated explanation thereof is omitted. Also, the following examples are not intended to limit the interpretation of the scope of the claims of the present invention.
[Configuration of conventional LCD panel]
FIG. 1 is an exploded perspective view showing a schematic configuration of a conventional liquid crystal display device for a mobile phone.
As shown in FIG. 1, a conventional liquid crystal display device includes a liquid crystal display panel (LCD) and a backlight (B / L) that irradiates the liquid crystal display panel (LCD).
The backlight (B / L) includes a light guide plate 6 having a substantially rectangular shape similar to the planar shape of a liquid crystal display panel (LCD), and a white light emitting diode (disposed on one side surface (incident surface)) of the light guide plate 6. A light source) 8, a reflection sheet 7 disposed on the lower surface (surface opposite to the liquid crystal display panel (LCD)) side of the light guide plate 6, and an upper surface (surface on the liquid crystal display panel side) of the light guide plate 6. An optical sheet group 5 and a resin mold frame (hereinafter simply referred to as a mold) 10. The optical sheet group 5 includes, for example, a lower diffusion sheet, two lens sheets, and an upper diffusion sheet.
The liquid crystal display panel (LCD) includes a pair of glass substrates (2a, 2b), an upper polarizing plate 1 attached to the upper surface (display surface) of the glass substrate 2a, and a lower surface (backlight side) of the glass substrate 2b. And the lower polarizing plate 3 attached to the surface.
A semiconductor chip 11 constituting a driver or the like is mounted on the glass substrate 2b. A flexible substrate that supplies a control signal or the like to the semiconductor chip 11 is mounted on the glass substrate 2b, but the flexible substrate is not shown in FIG.

[Configuration of Liquid Crystal Display Panel with Built-in Photosensor as Premise of the Present Invention]
FIG. 2 is a circuit diagram showing an equivalent circuit of a photosensor built-in liquid crystal display panel in which a photosensor is incorporated in one pixel, which is a premise of the present invention.
As shown in FIG. 2, a conventional liquid crystal display panel in which an optical sensor is incorporated in one pixel includes a liquid crystal scanning line (GL; also referred to as a gate line) and a video line (DL; a drain line or a source line). In addition to a thin film transistor (Tr2) for liquid crystal and a storage capacitor (C), it has a photosensor (PS), a sensor control line (PSL; there are a plurality of cases), and a sensor output line (OUT). . In some cases, the sensor control line (PSL) and the sensor output line (OUT) can be shared with the liquid crystal scanning line (GL) and the video line (DL).
The output of the optical sensor (PS) is output to the outside of the liquid crystal display panel and input to an external driver (liquid crystal data control IC or the like) (DRV). Thereby, the output of the photosensor (PS) is reflected on the liquid crystal display panel as liquid crystal data. In FIG. 2 and FIG. 4 described later, an arrow FA indicates the outside of the liquid crystal display panel.
3 is a schematic cross-sectional view showing a cross-sectional structure of one pixel in which the photosensor shown in FIG. 2 is incorporated. FIG. 3A shows a cross-sectional structure of a thin film transistor (Tr2), and FIG. The cross-sectional structure of a sensor (PS) is shown.
In FIG. 3, S is a source, G is a gate, D is a drain, SM is a semiconductor layer, K is a cathode, and A is an anode. The optical sensor (PS) has a PIN structure, for example, and generates a current for light. In addition, a light shielding film (BPS) is provided below the photosensor (PS) so that light from the backlight is not incident.

FIG. 4 is a circuit diagram showing an equivalent circuit of a liquid crystal display panel in which pixels in which photosensors are incorporated are arranged in an array.
The photosensor (PS) shown in FIG. 4 includes a photodiode (D1), a capacitor element (C1) that converts a current of the photodiode (D1) into a voltage, and thin film transistors (Tr1, Tr3) of a readout circuit. Note that the thin film transistor (Tr3) has one configuration for one vertical readout line because it is used as a common use. CLK1 and CLK2 are clock lines, and Vb is a bias line.
FIG. 5 shows the optical sensor section and readout circuit section in FIG. As shown in FIG. 5, the thin film transistors Tr1 and Tr3 form a source follower circuit, and impedance change is performed on a voltage change with respect to the light of the capacitive element (C1), and the result is output as a sensor output (SOUT).
In the circuit shown in FIG. 4, since the liquid crystal scanning line (GL) and the video line (DL) are not shared, the operation of the optical sensor (PS) can be performed asynchronously with the liquid crystal display. .

FIG. 6 is a timing chart of the circuit shown in FIG. 5. Hereinafter, the operation of the circuit shown in FIG. 5 will be described with reference to FIG.
First, the voltage of the clock line (CLK2) is set to a high level (hereinafter, H level), and charges are accumulated in the capacitor (C1). Then, the operation (sensing by light reception) of the photosensor (PS) starts from the time when the voltage of the clock line (CLK2) becomes the Low level (hereinafter, L level).
By irradiating the photodiode (D1) with light, charges accumulated in the capacitor (C1) are expelled to the clock line (CLK2), and as a result, the voltage Vo of the capacitor (C1) decreases. This is integrated by the sensor operating time, and the change in irradiation light is output as the voltage Vo of the capacitive element (C1).
Next, when the clock line (CLK1) becomes an H level voltage, the source follower circuit composed of the thin film transistors Tr1 and Tr3 starts to operate, and the voltage Vo of the capacitor (C1) at that time passes through the source follower circuit. Sensor output SOUT.
Therefore, the sensor light receiving time is from the time when the voltage of the clock line (CLK2) becomes L level to the time when the clock line (CLK1) becomes H level.
Note that the voltage Vo of the capacitive element (C1) and the wavy line of the sensor output (SOUT) in FIG. 6 are outputs in a dark state where no light is irradiated, and this difference is a voltage change with respect to the irradiated light.
The actual cross-sectional structure of one pixel in which the photosensor shown in FIG. 2 is incorporated is as shown in FIG. That is, a TFT substrate (T-SUB) in which an optical sensor or the like is produced on a substrate (SUB1) such as a glass substrate, and a color filter substrate (C in which a color filter or the like is produced on a substrate (SUB2) such as a glass substrate) -SUB), a liquid crystal layer (LC), and a backlight (B / L).
Although not shown in FIG. 7, a lower polarizing plate (3 in FIG. 1) is formed on the TFT substrate (T-SUB), and an upper polarizing plate is formed on the color filter substrate (C-SUB). (1 in FIG. 1) is formed.

[Example 1]
FIG. 8 is a timing chart for explaining a driving method of the optical sensor built-in liquid crystal display panel according to the first embodiment of the present invention.
The optical sensor built-in liquid crystal display panel (LCD) of this embodiment is a light source for irradiating light with a wavelength other than the visibility as a light source for the optical sensor (PS) (for example, a light source for invisible light such as infrared rays or ultraviolet rays). ) (LSP). In addition, the brightness of the light source (LSP) for the optical sensor (PS) can be changed intentionally, and information on the intensity can be added to distinguish between regular touch input and noise input caused by external light with high accuracy. It is.
Further, in this embodiment, one frame period is divided into an image display period for displaying an image on a liquid crystal display panel (LCD) (period in which B / L in FIG. 8 is ON), and a liquid crystal display panel (PS) by an optical sensor (PS). This is divided into a touch position detection period (period in which PS in FIG. 8 is ON) for detecting the touch position of the observer on the LCD).
That is, in this embodiment, within the image display period, the light source for the optical sensor (LSP) is turned off, the backlight (B / L) is turned on, the image is displayed on the liquid crystal display panel (LCD), and the touch position detection period. The light source for light sensor (LSP) is turned on and the backlight (B / L) is turned off, and the touch position of the observer on the liquid crystal display panel (LCD) is detected by the light sensor (PS).
As described above, in this embodiment, the lighting period of the backlight (B / L) for displaying an image on the liquid crystal display panel (LCD) and the light source for light sensor (LSP) that is input to the light sensor (PS). ) Is separated in time from the lighting time.
As a result, in this embodiment, the light from the backlight (B / L) is prevented from being input to the photosensor (PS) and the input light to the photosensor (PS) is reduced as in the prior art. Since only the sensor light source (LSP) can be used, the detection sensitivity can be improved.
In this embodiment, in addition to the white light-emitting diode 8 shown in FIG. 1, a light source (for example, invisible such as infrared rays or ultraviolet rays) that emits light having a wavelength other than the visibility is used in the backlight (B / L). Needless to say, it is necessary to dispose a light source (LSP).

[Example 2]
FIG. 9 is a timing chart for explaining a driving method of the optical sensor built-in liquid crystal display panel according to the second embodiment of the present invention.
The present embodiment is an embodiment in which the present invention is applied to a field sequential type photosensor built-in liquid crystal display panel.
In the photosensor built-in liquid crystal display panel (LCD) of the present embodiment, the above-described image display period is the first period during which a red image is displayed (period in which B / LR in FIG. 9 is ON), and the green display period. In a second period for displaying an image (period in which B / LG in FIG. 9 is ON) and a third period in which a blue image is displayed (period in which B / LB in FIG. 9 is ON). Divided into three.
That is, in this embodiment, the light source (LSP) for photosensors is turned off and red (R) is emitted from the backlight (B / L) within the first image display period, and the liquid crystal display panel (LCD) is red. In the second image display period, the light source for the optical sensor (LSP) is turned off, and the backlight (B / L) emits green (G) to the liquid crystal display panel (LCD). A green image is displayed, and the light source (LSP) for the optical sensor is turned off and blue (B) is emitted from the backlight (B / L) within the third image display period, and a liquid crystal display panel (LCD) In the touch position detection period, the light source for the optical sensor (LSP) is turned on, the backlight (B / L) is turned off, and the liquid crystal display panel (LCD) is displayed by the optical sensor (PS). The touch position of the upper observer is detected.
Thus, also in the present embodiment, the lighting period of the backlight (B / L) for displaying an image on the liquid crystal display panel (LCD) and the light source for light sensor (LSP) that is input to the light sensor (PS). ) Is separated in time from the lighting time.
As a result, in this embodiment, the light from the backlight (B / L) is prevented from being input to the photosensor (PS) and the input light to the photosensor (PS) is reduced as in the prior art. Since only the sensor light source (LSP) can be used, the detection sensitivity can be improved.

In this embodiment, in the backlight (B / L), instead of the white light emitting diode 8 shown in FIG. 1, a red light emitting diode that emits red (R) and a green light emitting that emits green (G). It is necessary to dispose a diode, a blue light emitting diode that irradiates blue (B), and a light source (for example, a light source for invisible light such as infrared rays or ultraviolet rays) (LSP) that emits light having a wavelength other than visibility. Needless to say.
Further, in each of the above-described embodiments, when the touch position detection period (sensor light receiving time shown in FIG. 6) is insufficient, the sensor output SOUT may be integrated over several frames to increase the detection sensitivity. Good.
As is well known, in a field sequential type liquid crystal display panel with a built-in photosensor, a normal liquid crystal display in which the number of pixels is composed of, for example, three sub-pixels of R, G, and B, for example. One third of the number of pixels of the panel.
In the above description, the embodiment in which the present invention is applied to a liquid crystal display panel with a built-in optical sensor for a mobile phone having a side edge type backlight (B / L) has been described. However, the present invention is not limited thereto. However, the present invention is also applicable to a photosensor built-in liquid crystal display panel having a direct type backlight (B / L).
As mentioned above, the invention made by the present inventor has been specifically described based on the above embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Of course.

DESCRIPTION OF SYMBOLS 1 Upper polarizing plate 2a, 2b, SUB1, SUB2 Glass substrate 3 Lower polarizing plate 5 Optical sheet group 6 Light guide plate 7 Reflective sheet 8 White light emitting diode (light source)
10 Mold 11 Semiconductor chip GL Scan line (Gate line)
DL video line (drain line or source line)
Tr1, Tr2, Tr3 Thin film transistor LC Liquid crystal C Retention capacitance PS Photo sensor PSL Sensor control line OUT Sensor output line DRV driver S Source G Gate D Drain SM Semiconductor layer K Cathode A Anode BPS Light shielding film D1 Photo diode C1 Capacitance element CLK1, CLK2 Clock line Vb Bias line C-SUB Color filter substrate T-SUB TFT substrate B / L Backlight LCD Liquid crystal display panel

Claims (6)

A display panel having a plurality of pixels;
At least one pixel of the plurality of pixels is a photosensor built-in display device having a photosensor,
A visible light source that emits visible light;
A light source for invisible light that emits invisible light,
One frame period is composed of an image display period and a touch position detection period.
Within the image display period, the high light source for invisible light is turned off, the light source for visible light is turned on, and an image is displayed on the display panel,
Built-in optical sensor, wherein the visible light source is turned off and the invisible light source is turned on within the touch position detection period, and the viewer's touch position on the display panel is detected by the optical sensor. Display device. The visible light source includes a first light source that emits light of a first color, a second light source that emits light of a second color, and a third light source that emits light of a third color. And
The image display period includes a first image display period in which the second light source and the third light source are turned off, the first light source is turned on, and an image of a first color is displayed on the display panel. A light source and a third light source are turned off, the second light source is turned on, a second image display period for displaying an image of the second color on the display panel, and the first light source and the second light source are turned off, The display device with a built-in optical sensor according to claim 1, further comprising a third image display period in which the third light source is turned on and an image of a third color is displayed on the display panel.   The display panel includes a light shielding film that prevents invisible light from the light source for invisible light from being incident on the photosensor from a surface opposite to the observer of the liquid crystal display panel. Item 3. The display device with a built-in optical sensor according to item 1 or item 2. The display panel is a liquid crystal display panel having a backlight,
4. The display device with a built-in optical sensor according to claim 1, wherein the visible light source and the invisible light source are arranged in the backlight. 5. The backlight has a light guide plate,
The display device with a built-in optical sensor according to claim 4, wherein the light source for visible light and the light source for invisible light are disposed on at least one side surface of the light guide plate.   The display device with a built-in photosensor according to claim 1, wherein the photosensor is configured by a photodiode.

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