JP5008016B2 - Display device - Google Patents

Description

The present invention relates to a display device, and more particularly to a display device that can automatically change the brightness of a light source without malfunctioning according to the brightness of external light in a display device having a light source such as a backlight or a front light.

In recent years, the application of liquid crystal display devices has rapidly spread not only in information communication equipment but also in general electric equipment. In particular, in the case of a portable type, a reflective type that does not require a backlight or a sidelight (hereinafter collectively referred to as “backlight etc.”) like a transmissive liquid crystal display device in order to reduce power consumption. However, since this reflection type liquid crystal display device uses outside light as a light source and is difficult to see in a dark room or the like, it uses a front light (see Patent Document 1 below). And a transflective liquid crystal display device having both transmissive and reflective properties has been developed (see Patent Document 2 below).

For example, a reflective liquid crystal display device using a front light displays an image by turning on the front light in a dark place and displays an image using outside light without turning on the front light in a bright place. Therefore, it is not necessary to always turn on the front light, so that power consumption can be greatly reduced. In addition, the transflective liquid crystal display device includes a transmissive portion having a transparent electrode and a reflective portion having a reflective electrode in one pixel. In a dark place, a backlight or the like is lit to turn on the pixel region. Since the image is displayed using the transmission part and the image is displayed using the external light in the reflection part without lighting the backlight or the like in a bright place, the backlight or the like is always turned on in this case as well. Since it is no longer necessary
The power consumption can be greatly reduced.

In the above-described reflective liquid crystal display device and transflective liquid crystal display device, the visibility of the liquid crystal display screen varies depending on the intensity of external light. For this reason, in order to make the liquid crystal display screen easier to see, the end user himself / herself determines whether or not the backlight or the front light should be turned on according to the intensity of the external light. It was necessary to perform a complicated operation of turning on, turning off, or turning off the light. Furthermore, even when the brightness of outside light is sufficient, the backlight or the like or the front light may be turned on unnecessarily. In such a case, useless power consumption increases. In such portable devices, there is a problem that the battery is consumed quickly.

As a conventional technique for dealing with such problems, an optical sensor is provided in a liquid crystal display device,
There is known an invention in which the light sensor detects the brightness of external light and controls on / off of a backlight or the like based on the detection result of the light sensor (see Patent Documents 3 to 5 below).

For example, in Patent Document 3 below, a thin film field-effect transistor (TFT) for light detection (see paragraph [0012]) is formed on a substrate of a liquid crystal display panel as an optical sensor, and a light leakage current of the TFT is detected. Automatically turn on / off the backlight according to the ambient brightness.
A liquid crystal display device that is turned off is disclosed.

Patent Document 4 listed below discloses a liquid crystal display device that uses a photodiode as an optical sensor and supplies a temperature-guaranteed current to a light-emitting diode as a backlight according to ambient brightness. .

Further, in Patent Document 5 below, a light emitting diode used as an operation display means of a backlight or a device is also used as an optical sensor, and the backlight is turned on based on an electromotive force of the light emitting diode corresponding to the ambient brightness. An invention of a portable terminal that controls the above is disclosed.
JP 2002-131742 A (Claims, FIGS. 1 to 3) JP 2001-350158 A (Claims, FIG. 4) JP 2002-131719 A (claims, paragraphs [0010] to [0013], FIG. 1) JP 2003-215534 A (claims, paragraphs [0007] to [0019], FIGS. 1 to 3) JP 2004-007237 A (claims, paragraphs [0023] to [0028], FIG. 1)

A liquid crystal display device that automatically turns on / off a backlight or the like by detecting ambient brightness using the conventional optical sensor as described above is a small portable device such as a mobile phone incorporating the liquid crystal display device. Therefore, the ambient brightness is usually detected by arranging one optical sensor in an empty area of a device incorporating a liquid crystal display device, and at a predetermined brightness determined in advance based on the output of the optical sensor. The backlight is automatically turned on / off.

However, in the case of a configuration in which one light sensor is arranged in an empty area of a device incorporating a liquid crystal display device and the surrounding brightness is detected, for example, the light sensor is blocked by an unintentional operation by a user's finger. If the light sensor momentarily shines or is blocked by the influence of the surrounding environment, the brightness of the backlight fluctuates frequently, and the backlight cannot always be maintained at the desired brightness. was there.

In addition, in order to place the optical sensor in the vacant area of the device incorporating the liquid crystal display device,
Although it is necessary to provide a special opening in the device so that external light can enter the optical sensor, there is a problem that the height and shape of the device are restricted.

The present invention has been made to solve the problems of a display device that automatically turns on / off a backlight or the like by detecting ambient brightness with the above-described conventional optical sensor. It is an object of the present invention to provide a display device that is not easily affected by unintentional operation or ambient environment, and that can automatically and stably control the brightness of a backlight.

In order to achieve the above object, the present invention is characterized by adopting the following configuration. That is, in a display device including a display panel including an active matrix substrate and illumination means for the display panel, a plurality of unshielded light beams arranged in at least one line along the periphery of the display area of the display panel A first photosensor array having a sensor, and a second photosensor array having a plurality of light-shielded photosensors arranged on the inner peripheral side of the first photosensor array, the second light Based on the output of the light detection unit that outputs an average value of the output of the light-shielded photosensor of the sensor row and the average value of the output of the non-light-shielded photosensor of the first photosensor row possess a control unit for controlling the light emission intensity of the illuminating means, the light sensor is not shielded form a light-shielded optical sensor and the first optical sensor array form a second optical sensor columns, thin film field effect transistor The first light cell The source electrode, gate electrode, and drain electrode of each thin film field effect transistor forming the array are connected in parallel to each other, and a capacitor is connected between the source electrode and the drain electrode, and the source electrode and a predetermined low voltage power source The first switch element is connected between the source electrode, the source electrode, the gate electrode, and the drain electrode of the thin film field effect transistor forming the second photosensor array, and the source electrode and the drain electrode are connected in parallel. In the display device, a capacitor is connected therebetween, and a second switch element is connected between the source electrode and a predetermined low voltage power source .

By providing the above-described configuration, the present invention has the following excellent effects. That is, since several optical sensors multi are arranged in at least one row, momentarily light to the light sensor by the influence of and the ambient environment, such as light sensors are shielded by involuntary movements of the user's finger Even if the light is shined or blocked, the average output of the light sensors does not fluctuate so much because all of the light sensors arranged in a row are not affected at the same time. Will not fluctuate frequently. In addition, since the plurality of photosensors are arranged along the periphery of the display area of the display panel, it is not necessary to provide a special configuration for allowing external light to hit the photosensors. At the same time, the degree of freedom in designing the display device increases. As a photosensor, an arbitrary photo-electric conversion element such as a well-known photodiode, phototransistor, thin film field effect transistor type photo detector (TFT photosensor), photo SCR, photoconductor, photocell, etc. is appropriately selected. Can be used.

Further, since the dark reference output by the output of the optical sensor that is shielding light has the same temperature characteristics as the optical sensor is not shielded with stabilized, the optical sensor is not blocked even when the ambient temperature change characteristic Is compensated by the characteristics of the light-shielded light sensor, so that the brightness of the outside light can be measured accurately and the illumination means can be automatically turned on / off accurately at a predetermined predetermined brightness. become. In addition, since the same lot product is normally used for both the light-shielded light sensor and the light-shielded light sensor, there is less variation in characteristics, so the illumination means is automatically operated with a predetermined brightness that is accurately determined in advance. ON / OFF control can be performed .

In particular , since the display unit of the display device is provided with a black matrix provided around the color filter substrate, the black matrix can be obtained by providing a light-shielded photosensor on the inner peripheral side of the non-light-shielded photosensor. it is possible to cover the light sensor in only slightly widened, and eliminates the need to provide a member for separately shading, better structural and aesthetically appearance.

Further, the light sensor is shielded, if adjacent an optical sensor which is not shielded, the characteristics of the two sensors for it is made is close characteristics adjacent the location, variation in characteristics is reduced, The illumination means can be automatically turned on / off accurately at a predetermined brightness.

Further, TFT as an optical sensor, lever provided a capacitor and a switch element, it is not necessary to increase the number of manufacturing steps, moreover, it is not necessary to particularly increase the size of the display panel. In addition, since the leakage current when a reverse bias voltage is applied to the gate electrode of a TFT as an optical sensor is proportional to the light intensity, the output voltage of each capacitor after a predetermined time has elapsed based on the switching element being turned off. In addition, since the average value of the output of a plurality of light-shielded TFTs and the average value of the output of a plurality of non-light-shielded TFTs can be detected, the average intensity of light that is accurately temperature compensated can be detected. Thus, the illumination means can be automatically turned on / off accurately at a predetermined brightness.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. The embodiment described below is an example of an active matrix display device for embodying the technical idea of the present invention. However, the present invention is not intended to be limited to this embodiment, and the present invention is not limited to the technical ideas described in the claims. It can be equally applied to those that have been changed.

First, the operation principle and driving circuit of a TFT as an optical sensor (hereinafter referred to as “TFT optical sensor”) will be described with reference to FIGS. FIG. 1 is a diagram showing an example of a voltage-current curve of a TFT photosensor, FIG. 2 is a circuit diagram of a light detection unit using the TFT photosensor, and FIG. 3 shows a case where brightness is different. It is a figure which shows the voltage-time curve of the both ends of the capacitor | condenser in the circuit diagram shown in FIG.

The TFT photosensor has substantially the same configuration as a TFT used as a switching element of an active matrix liquid crystal display panel. This TFT photosensor is shown in FIG.
As shown in Fig. 4, when the light is shielded, a very small dark current flows in the gate-off region. However, when light hits the channel part, the leakage current depends on the intensity (brightness) of the light. It has the characteristic of becoming larger. Therefore, as shown in the circuit diagram of the light detection unit 33 in FIG.
Constant reverse bias voltage as a gate-off region to the gate electrode G _L of the T light sensor (e.g., -1
0V) applied to, and a capacitor C in parallel between the drain electrode D _L and the source electrode S _L, is applied to both ends of the capacitor C a constant voltage Vs (for example, + 2V) turns on the switch SW After that, when the switch element SW is turned off, the voltage across the capacitor C becomes TFT.
As shown in FIG. 3, it decreases with time according to the brightness around the optical sensor. Accordingly, if the voltage across the capacitor C is measured after a predetermined time t ₀ after the switch element SW is turned off, an inversely proportional relationship is established between the voltage and the brightness around the TFT photosensor.
The brightness around the T light sensor can be obtained.

Next, taking a transflective liquid crystal display device as an example of an active matrix display device, a manufacturing method of the photodetection unit including the above-described TFT photosensor as well as its manufacturing method, and the obtained transflective liquid crystal display device The configuration will be described with reference to FIGS. 4 is a plan view of one pixel showing the color filter substrate of the transflective liquid crystal display device in perspective, and FIG. 5 is a cross-sectional view taken along the line AA of FIG. 4 excluding the color filter substrate. 6 is a plan view of the transflective liquid crystal display device, FIG. 7 is a cross-sectional view of the light detection unit, and FIG. 8 is a circuit diagram showing an example of electrical connection of a plurality of light detection units. Is a circuit diagram of a modification of FIG. 8, and FIG. 10 is a modification of the transflective liquid crystal display device of FIG.

As shown in FIGS. 4 and 5, the transflective liquid crystal display device 10 includes a plurality of scanning lines 12 made of a metal such as aluminum or molybdenum on a display region of a transparent glass substrate 11 at equal intervals. In addition, the auxiliary capacitance line 21 is formed in parallel with the scanning line 12 at the approximate center between the adjacent scanning lines 12, and the gate electrode G of the TFT extends from the scanning line 12. Has been.

Further, a gate insulating film 14 made of silicon nitride, silicon oxide or the like is laminated on the glass substrate 11 so as to cover the scanning lines 12, the auxiliary capacitance lines 21, and the gate electrodes G.
A semiconductor layer 22 made of amorphous silicon, polycrystalline silicon, or the like is formed on the gate electrode G via a gate insulating film 14, and the gate insulating film 14 is made of a metal such as aluminum or molybdenum. A plurality of signal lines 13 are formed so as to be orthogonal to the scanning lines 12, TFT source electrodes S are extended from the signal lines 13, and the source electrodes S are in contact with the semiconductor layer 22. Further, a drain electrode D, which is formed of the same material as the signal line 13 and the source electrode S and is simultaneously formed, is provided on the gate insulating film 14, and the drain electrode D is also in contact with the semiconductor layer 22.

Here, a region surrounded by the scanning lines 12 and the signal lines 13 corresponds to one pixel. The gate electrode G, the gate insulating film 14, the semiconductor layer 22, the source electrode S, and the drain electrode D constitute a TFT serving as a switching element, and this TFT is formed in each pixel. In this case, the storage capacitor of each pixel is formed by the drain electrode D and the storage capacitor line 21.

A protective insulating film 23 made of, for example, an inorganic insulating material is laminated so as to cover the signal lines 13, TFTs, and the gate insulating film 14, and an interlayer film 17 made of an organic insulating film is laminated on the protective insulating film 23. ing. On the surface of the interlayer film 17, fine uneven portions are formed in the reflection portion 15 and flat in the transmission portion 16. 4 and 5, the uneven portion of the interlayer film 17 in the reflection portion 15 is omitted. A contact hole 20 is formed in the protective insulating film 23 and the interlayer film 17 at a position corresponding to the drain electrode D of the TFT. In each pixel, a reflective electrode 18 made of, for example, aluminum metal is provided on the reflective portion 15 on the contact hole 20 and a part of the surface of the interlayer film 17,
A pixel electrode 19 made of, for example, ITO is formed on the surface of the reflective electrode 18 and the surface of the interlayer film 17 in the transmissive portion 16.

A backlight or a sidelight having a well-known light source, a light guide plate, a diffusion sheet, etc. (not shown) is disposed below the glass substrate 11, and the surface of the pixel electrode 19 is covered with all the pixels. An alignment film (not shown) is laminated, and a color filter substrate (not shown) provided with R, G, B color filters, counter electrodes, etc. formed corresponding to each pixel. The transflective liquid crystal display device 10 can be obtained by facing the glass substrate 11 and providing a sealant around both substrates to bond the substrates together and injecting liquid crystal between the substrates.

In this case, if the reflective electrode 18 is omitted, a transmissive liquid crystal display device is obtained.
Is provided over the entire lower portion of the pixel electrode 19, a reflective liquid crystal display device is obtained. However,
In the case of a reflective liquid crystal display device, a front light is used instead of a backlight or side light.

In the transflective liquid crystal display device 10 according to this embodiment, a number of scanning lines 12, signal lines 13, pixel electrodes 19 and the like as described above are arranged in a matrix, and as shown in FIG. 30, and a driver IC 31 for driving the transflective liquid crystal display device 10 is provided at the periphery of the display region 30, and the periphery of the display region 30 opposite to the side where the driver IC 31 is provided is provided. For example, a plurality of (for example, three in one row × two rows = total six) TFT photosensor units, two rows of photodetecting units 33 integrally including a capacitor C and a switch element SW composed of one TFT. ₁ and 33 ₂ are formed.

Of the two rows of light detection units 33 ₁ and 33 ₂ , the light detection unit 33 in the row outside the display region 30.
₁ TFT ambient light photosensors ₃₂₁ to 323 has not been shielded, the light detector 33 ₂ of the inner column T
Since the FT light sensors 32 _{4 to} 32 ₆ are substantially the same except for being shielded,
Hereinafter will be described a specific configuration taking as an example the optical detector 33 _first outer not shielded from light.

Light detection unit 33 _1, as shown in FIG. 7, the gate electrode _G L1 _{~G L3} of the TFT ambient light photosensor on the surface of the glass substrate 11, one electrode _Ce 1 ～Ce capacitor _C 1 -C _{6 3} and the 1 and gate electrode G _S1 of the TFT constituting the switching element SW ₁ is formed, the gate insulating film 14 made of silicon oxide or silicon nitride so as to cover these surfaces are stacked.

Then, via the TFT ambient light photosensors ₃₂₁ to 323 respectively gate insulating film 14 above the gate electrode _{G S1} of the TFT constituting the upper and the first switching element SW ₁ of the gate electrode _G L1 _{~G L3} of ₃ non Semiconductor layers 22 _{L1 to} 22 _{L made of} crystalline silicon or polycrystalline silicon
₃ and 22 _S1 are formed, and the source electrodes S _{L1 to} S _L3 and the drain electrodes D _{L1 to} D _L3 of the TFT photosensors 32 _{1 to} 32 _{3 made} of a metal such as aluminum or molybdenum are formed on the gate insulating film 14. The source electrode S _S1 and the drain electrode D _{S1 of} the TFT constituting _one switch element SW ₁ are provided so as to be in contact with the respective semiconductor layers 22 _{L1 to} 22 _L3 and 22 _S1 .

Among these, the source electrodes S _{L1 to} S _L3 of the TFT photosensors 32 _{1 to} 32 ₃ are extended to form the other electrodes Ce ₁ ′ to Ce ₃ ′ of the capacitors C _{1 to} C ₃ , and the TFT photosensors The 32 ₃ source electrode S _L3 is connected to the drain electrode D _{S1 of the} TFT constituting the _first switch element SW ₁ .

Further, a protective insulating film 23 made of, for example, an inorganic insulating material is laminated so as to cover the surfaces of the TFT photosensors 32 _{1 to} 32 ₃ , capacitors C _{1 to} C ₃ and the first switch element SW _{1 made} of TFT. , the first surface of the switch elements SW _1, in order to prevent the influence of external light, are covered with the black matrix 24.

The TFT ambient light photosensors _{321 to} 323, a capacitor _C 1 -C ₃ and the light detecting portion 33 ₁ having integrally a first switching element SW ₁ consisting of TFT, the insulating layer of the same layer in FIGS. 5 and 7 Are assigned the same reference numerals, and the corresponding constituent parts of the respective TFTs are distinguished from each other by providing the same reference numerals with subscripts, so that they are formed at the same time when the switching TFTs in the display region 30 are formed. In this embodiment, as shown in FIG. 6, a plurality of light detection units 33 ₁ and 33 ₂ are arranged in two.
Was placed in a column, in a row of the photodetecting section 33 ₂ located inside when viewed from the one display area 30, the black surface of the gate electrode _G L4 _{~G L6} portion of at least the TFT ambient light sensor ₃₂ 4-32 ₆ Covered with a matrix to block light. With such a configuration, the light detection unit 33
_Since the output of ₂ is not affected by outside light, it becomes a dark reference output.

The light can be shielded by using a black matrix around a color filter substrate (not shown). In this case, since the display unit of the display device is provided with the black matrix provided around the color filter substrate, it is possible to cover the TFT photosensors 32 _{4 to} 32 ₆ by slightly widening the black matrix. Therefore, there is no need to provide a separate light shielding member, and the appearance is improved in terms of structure and appearance.

A plurality of electrical connections of the optical detector 33 ₁ and 33 ₂ in this embodiment will be described with reference to FIG. In this embodiment, the light detector 33 ₁ of the TFT ambient light photosensors ₃₂₁ to 323 the source electrodes of the _S L1 _{to S L3} are connected in parallel to each other first switching element constant voltage via the SW ₁ Vs (e.g., + 2V) is connected to the signal line S output signal to the outside it has been retrieved by _S, further, each of the gate electrodes G _L1 ~G _L3 are connected in parallel to each other constant reverse bias voltage (e.g., - 10V) is applied, and each drain electrode D _L1 ~
_DL6 are also connected in parallel to each other and connected to a predetermined voltage source VCOM.

Similarly, each of the TFT ambient light photosensor ₃₂ of the light detecting portion 33 ₂ 4-32 ₆ the source electrode S of the
_{L4 to} S _L6 are connected in parallel to each other, and are connected to a constant voltage V via the _second switch element SW2.
is connected to the s, the signal lines S _R are taken out output signals to the outside by further gate electrodes G _L4 ~G _L6 are connected in parallel the same constant reverse the light detector 33 ₁ side bias voltage is applied, and each drain electrode D _L1 to D _L6 also connected in parallel to each other are connected to the same predetermined voltage source VCOM the light detector 33 _1.

In this embodiment, the average output of the TFT ambient light photosensors ₃₂₁ to 323 that are not shielded from light to obtain the signal lines _{S S,} the average of the TFT ambient light photosensors ₃₂ 4-32 ₆ which is shielding the signal lines _{S R} Since the output is obtained, when the signal appearing on the signal lines S _R and S _S is processed, the unshielded TFT photosensor 32 based on the average value of the output of the shielded TFT photosensors 32 _{4 to} 32 _6.
The average value of the output of the _{1-32 3} is obtained.

Using this output, on / off of the illumination means is controlled by a separately known control means. Note that processing of signals appearing on the signal lines S _R and S _S may obtain a differential output, or may perform arithmetic processing so as to have a predetermined relationship. The control means separately photodetector unit 33 ₁ and 3
3 may be provided in the vicinity of _2, or may be provided in the driver IC 31.

Since the TFT light sensors 32 _{1 to} 32 ₃ that are not shielded are arranged at intervals in a line along the periphery of the display region 30 as shown in FIG. even if that block the TFT ambient light photosensors ₃₂₁ to 323 with a finger or the like, because it is rare that all of the TFT ambient light photosensors ₃₂₁ to 323 is shielded at the same time, TFT light sensor 3 not shielded
The average value of 2 _{1 to} 32 ₃ does not fluctuate greatly, and the brightness of the backlight or the like does not fluctuate frequently.

The reason for providing the light-shielded TFT photosensors 32 _{4 to} 32 ₆ as described above is that the TFT
This is because the light detection characteristics of the optical sensor vary greatly depending on the temperature, but the temperature characteristics of the unshielded TFT optical sensors 32 _{1 to} 32 ₃ are compensated by the shielded TFT optical sensors 32 _{4 to} 32 _6. With this configuration, it is possible to accurately control on / off of the backlight or the like with a desired brightness even if the temperature changes. However, if temperature compensation is not required, the light detection unit 33 ₂ and the TFT photosensors 32 _{4 to} 32 ₆ that are shielded from light can be omitted.

In this case, the capacitors C _{1 to} C ₃ and C _{4 to} C ₆ are also connected in parallel, so that one capacitor can be used for each. However, since the necessary capacity is increased, FIG. It is better to provide them individually as shown in FIG.

In a modification of the above embodiment, as shown in FIG. 9, the source electrodes _S L1 _{to S L3} of the light detecting portion 33 ₁ of the TFT ambient light photosensors ₃₂₁ to 323 are first to independently The third switch elements SW _{1 to} SW ₃ are connected to a common constant voltage V _S (for example, +2 V) and are independently connected to the output wirings S _{S1 to} S _S3 , respectively. The gate electrodes G _{L1 to} G _L3 are connected in parallel to each other and have a constant reverse bias voltage (for example, −10 V).
Further, the drain electrodes D _{L1 to} D _L6 are also connected in parallel to each other and connected to a predetermined voltage source VCOM.

Similarly, each of the TFT ambient light photosensor ₃₂ of the light detecting portion 33 ₂ 4-32 ₆ the source electrode S of the
_L4 to S _L6, together are each independently connected to the fourth to sixth switching element _SW 4 to SW ₆ a constant voltage _{V S} of the same common light detector 33 ₁ side via the, independent of each other is connected to the output lines _S R1 _{to S R3} Te, further, each of the gate electrodes _G L4 _{~G L6} is in the same constant reverse bias voltage to the optical detector 33 ₁ side is applied are connected in parallel to each other, each drain electrode _D L4 _{to D L6} also connected in parallel to each other are connected to the same predetermined voltage source VCOM the light detector 33 _1.

In this modification, the output wirings S _{S1 to} S _{S3 of the} light detection unit 33 ₁ that is not shielded from light are transmitted to TF.
The outputs of the T light sensors 32 _{1 to} 32 ₃ are obtained. Therefore, the user can use a finger etc.
When any _{one of the} T light sensors 32 _{1 to} 32 ₃ is blocked, the output of any one of the output wirings S _{S1 to} S _S3 becomes a value far from the other outputs, so that the TFT easily blocked by the user When the average value is obtained by excluding outputs far from other outputs by a control device (not shown), this average value is substantially the same as the average value before the user blocks the TFT photosensor. Therefore, it is determined that the ambient brightness has not changed, and the brightness of the backlight or the like does not frequently change.

In the above modification, it was used which has the same arrangement as the optical detector 33 ₁ also has not been blocked by the light-shielded photodetector unit 33 ₂ side side, With this structure ,
Separately no longer necessary to prepare ₂ different configurations of light-shielded photodetector unit 33 and the light-shielded photodetector unit 33 _1, black light-shielded detector 33 ₂ is simply shielded non detector 33 _first surface It is economical because it can be obtained simply by covering with a matrix. In addition, since the same lot product is normally used for both the light-shielded light sensor and the light-shielded light sensor, variations in characteristics of both are reduced.

However, the output of each TFT ambient light sensor ₃₂ 4-32 ₆ light shielding light detector 33 ₂ side, even block the TFT ambient light photosensors ₃₂ 4-32 ₆ the user has been blocked by a finger or the like, substantially because it does not change, as the light-shielding light side detection unit 33 _2, as shown in FIG. 8, TFT
By connecting the source electrodes S _{L4 to} S _{L6 of the} optical sensors 32 _{4 to} 32 ₆ in parallel, one switch element and one output wiring can be provided.

In the above embodiment and modification, an example of arranging in parallel shielding light detector 33 ₁ and light-shielding are not even the light detector 33 ₂ adjacent one each row, thus 2 The two detectors 33 ₁ and 3 ₂ are arranged close to each other so that the temperature of the two does not differ and the variation in the measured value is reduced, so that the illumination means is accurately used with a predetermined brightness. automatically, but in order to be able to turn on / off control, may also be used with an integrated optical detector 33 ₂ which is not further advanced light detector 33 which is shielded by the _first and shading.

Further, an example which is provided along the periphery of the side opposite to the side where the driver IC31 of the display area 30 is provided in the liquid crystal display device a plurality of light detector 33 ₁ and 33 ₂ in the above embodiment to modification However, as shown in FIG. 10, it may be arranged between the driver IC and the display area 30, and may further be arranged on the side surface of the display area 30. In the modified example shown in FIG. 10 or arranged on the side surface of the display area, signal lines or scanning lines for connecting the display area 30 and the driver IC 31 are arranged. It is necessary to arrange the portions 33 _{1 to} 33 ₆ and necessary wiring between signal lines or scanning lines, or to form laminated wiring.

Moreover, although the example which uses what consists of TFT as an optical sensor was shown in the said Example, photoconductors, photocells, such as not only this but a photodiode, a phototransistor, photoSCR, CdS, etc. can also be used. .

Next, the plurality of photodetecting portions 33 ₁ and 33 _{2 of} the liquid crystal display device 10 obtained in this way.
An example of the backlight control unit 40 for performing on / off control of the backlight or the like using the output of will be described with reference to the block diagram shown in FIG. The backlight control unit 40 applies a constant to the source electrode _{S S} of the TFT constituting the switching element SW reference voltage Vs (e.g. + 2V) by the sensor control unit 41 turns on / off the TFT to also gate electrode Gs Voltage (for example, ± 10V) for switching, and a constant voltage (for example, −10V) for operating the TFT photosensor in the gate-off region is applied to the gate electrode _GL of the TFT photosensor. the drain electrode D _L of the sensor is adapted to apply a common potential VCOM. Then, the output of the optical detector 33 ₁ and 33 ₂ performs predetermined arithmetic processing by the sensor control unit 41 to obtain a measured value corresponding to the brightness of the outside light, as well as input to one terminal of the comparison unit 42 Also input to the mode control unit 43.

The mode control unit 43 is a circuit that switches between the normal operation mode initial setting mode by an external input signal. In the initial setting mode, the output of the sensor control unit 41 is input to the threshold storage unit 46 to be stored, and the normal operation is performed. In the mode, the output of the sensor control unit 41 is cut off, and the threshold value storage unit 44 outputs the stored threshold value to the other terminal of the comparison unit 42.

In the normal operation mode, the comparison unit 42 compares the input signal from the sensor control unit 41 with the input signal from the threshold storage unit 44, and the input signal from the sensor control unit 41 is stored in the threshold storage unit 44. If it is larger (brighter) than the threshold value, the backlight 46 is turned off via the switching unit 45, and conversely, the input signal from the sensor control unit 41 is smaller than the threshold value stored in the threshold value storage unit 44. In the case of (dark), the backlight or the like 46 is turned on via the switching unit 45.

In the mode control unit 43, when the initial setting mode is selected, since adapted to store the output from the sensor control unit 41 in the threshold storage unit 44, a predetermined in light detector 33 _to 333 ₆ By irradiating light of brightness, a threshold corresponding to the brightness of the light can be stored. Therefore, even if there are variations in the optical-electrical characteristics of the optical sensor, the backlight 46 can be accurately turned on / off with a predetermined brightness as a boundary.

In this case, the light having a predetermined brightness may be uniformly determined in the manufacturing process, or the end user may automatically turn on / off the backlight or the like with an appropriate brightness according to the preference. Good. Note that the comparison unit 42 may be provided with hysteresis characteristics so that the brightness when turning on and the brightness when turning off are changed, that is, the backlight is not frequently turned on / off. This hysteresis characteristic can be easily achieved by using a hysteresis comparator as the comparator 42.

In this embodiment, in order to be able to manufacture the photodetecting portions 33 ₁ and 3 ₂ at the same time as the TFT used as the switching element of the liquid crystal display panel, the periphery of the display region of the glass substrate 11 is used. Although the example provided on the frame is shown, it may be provided in the peripheral portion in the display area. Further, if the light detection units 33 ₁ and 33 ₂ themselves do not need to be manufactured at the same time as the TFT used as a switching element of the liquid crystal display panel, they are provided outside the liquid crystal display panel and are wired separately from the liquid crystal display panel. May be electrically connected.

Further, in this embodiment, the switch element of the optical detector 33 ₁ and 33 ₂ is also, an example of using a material obtained by laminating and integrating a capacitor or the like, can be formed in separate elements. When this switch element is an individual element, the installation location of the switch element can be arbitrarily set, and can be provided on the frame around the display area of the glass substrate 11 or provided outside the panel. It can also be incorporated into the driver IC.

In addition, the sensor control unit 41, the comparison unit 42, the mode control unit 43, the threshold value storage unit 44, and the switching unit 45 can be incorporated in a driver IC of the liquid crystal display device. The threshold storage unit does not have to be provided inside the liquid crystal display device 10, but in this case, the liquid crystal display device 10 is initialized from the host PC provided with the external threshold storage unit when the power of the liquid crystal display device 10 is turned on. It only has to be configured.

It is a figure which shows an example of the voltage-current curve of a TFT optical sensor. It is a circuit diagram of the photon detection part which uses a TFT photosensor. It is a figure which shows the voltage-time curve of the both ends of the capacitor | condenser in the circuit diagram shown in FIG. 2 in case brightness differs. FIG. 3 is a plan view of one pixel that is seen through a color filter substrate of a transflective liquid crystal display device. It is AA sectional drawing of FIG. 4 which excluded the color filter board | substrate. It is a top view of the transflective liquid crystal display device of an Example. It is sectional drawing of a photon detection part. It is a circuit diagram which shows the example of an electrical connection of a some photon detection part. It is a modification of the circuit diagram of FIG. It is a modification of the transflective liquid crystal display device of FIG. It is a block diagram of a backlight control unit.

Explanation of symbols

10 transflective liquid crystal display device 30 display area 31 driver IC
32, 32 ₁ to 32 ₆ TFT optical sensor 33 _1, 33 ₂ optical detector 40 backlight control section 41 the sensor control unit 42 comparing unit 43 mode control unit 44 threshold value controller 45 switching unit 46 backlights

Claims (5)

In a display device comprising a display panel comprising an active matrix substrate and illumination means for the display panel,
A first photosensor array having a plurality of unshielded photosensors arranged in at least one row along the periphery of the display area of the display panel, and arranged on the inner peripheral side of the first photosensor array. A second photosensor array having a plurality of light-shielded photosensors, an average value of the output of the light-shielded photosensors of the second photosensor train, and the first photosensor train A light detection unit that outputs an average value of the output of the unshielded light sensor;
A control unit for controlling the light emission intensity of the illumination means based on the output of the light detection unit;
I have a,
The light-shielded photosensor forming the second photosensor array and the non-light-shielded photosensor forming the first photosensor array comprise thin film field effect transistors,
The source electrode, the gate electrode, and the drain electrode of each of the thin film field effect transistors forming the first photosensor array are connected in parallel to each other, and a capacitor is connected between the source electrode and the drain electrode. A first switch element is connected between the source electrode and a predetermined low voltage power source,
Source electrodes, gate electrodes, and drain electrodes of the thin film field effect transistors that form the second photosensor array are connected in parallel to each other, and a capacitor is connected between the source electrode and the drain electrode. A second switch element is connected between the source electrode and a predetermined low voltage power source.
Display device.   2. The light-shielded photosensor forming the second photosensor array and the non-shielded photosensor forming the first photosensor array are each arranged in parallel at least in one row. Display device.   3. The display device according to claim 1, wherein the light-shielded photosensor forming the second photosensor array and the non-shielded photosensor forming the first photosensor array are adjacent to each other. One first switch element is disposed for the first photosensor array, and one second switch element is disposed for the second photosensor array,
The controller turns off the first switch element and the second switch element while applying a reverse bias voltage to the gate electrode for each of the first photosensor array and the second photosensor array. The display device according to claim 1, wherein an output voltage of the capacitor after a predetermined time is obtained as an average output of each of the first photosensor array and the second photosensor array. One first switch element is arranged for each thin film field effect transistor forming the first photosensor array, and one first switching element is formed for each thin film field effect transistor forming the second photosensor array. 2 switch elements are arranged,
The controller applies a reverse bias voltage to the gate electrode for each of the thin film field effect transistors forming the first photosensor array and the thin film field effect transistors forming the second photosensor array. The average of the remaining output voltages excluding output voltages far from the output voltages of the respective capacitors after a predetermined time from turning off the first switch element or the second switch element corresponding to the thin film field effect transistor The display device according to claim 1, wherein a value is obtained as an average value of each of the first photosensor array and the second photosensor array.

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