JP2007316243A - Display device and method for controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device for which an accurate illuminance calculation is made, and with which light quantity of a backlight is adequately controlled. <P>SOLUTION: The display device (for example a liquid crystal display device 1) is equipped with an array substrate 2 and a counter substrate 3, wherein a liquid crystal layer 4 is interposed between them so as to form a display region A. An optical sensor to measure external light illumination (an optical sensor 12 for external light illuminance measurement), and a temperature sensor 13 to measure the temperature are set on the array substrate 2. The optical sensor 12 for external light illuminance measurement and the temperature sensor 13 are integrally formed on the array substrate 2. By correcting an output of the optical sensor 12 for external light illuminance measurement with an output of the temperature sensor 13, external light illumination is accurately measured irrespective of the temperature. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a display device such as a liquid crystal display device and a control method thereof, and more particularly to an improvement of a display device provided with an optical sensor for monitoring external light illuminance.

  In recent years, liquid crystal display devices having features such as light weight, thinness, and low power consumption are widely used as display devices for information devices such as personal computers and word processors, and display devices for video devices such as televisions, video movies, and car navigation systems. . In many cases, such a liquid crystal display device has a built-in backlight that irradiates illumination light from behind the display element in order to realize a bright display screen.

  Incidentally, one of the advantages of the liquid crystal display device is its low power consumption, but generally the power consumption of the backlight is larger than that of the liquid crystal panel. On the other hand, in general, in a liquid crystal display device, in order to obtain sufficient visibility, it is necessary to increase the display luminance as much as possible. If the backlight is set to be bright in response to this, it is a factor that impairs the low power consumption. Become.

  Therefore, it has been studied to adjust the brightness of the backlight in accordance with the ambient illuminance (external light illuminance) to suppress power consumption as much as possible. For example, the brightness required to obtain sufficient visibility differs depending on whether the ambient illuminance is low, such as at night, or when the ambient illuminance is high, such as outdoors in the daytime in fine weather. It is considered that power consumption can be suppressed by adjusting the illuminance of the backlight to the minimum.

  In order to achieve this, in a liquid crystal display device using a thin film transistor, a proposal has been made in which an optical sensor (photosensor) is installed outside the display area of the substrate, and the brightness of the backlight is adjusted using the output. (See, for example, Patent Document 1 and Patent Document 2).

  Patent Document 1 discloses a liquid crystal display panel, a backlight that emits light from the back side of the liquid crystal display board, a controller that adjusts the amount of light of the backlight, and a photodetector that is arranged side by side with the liquid crystal display board. A liquid crystal display device is disclosed in which ambient light is detected by the light detector, the controller is adjusted, and the amount of light of the backlight is adjusted.

Patent Document 2 discloses a backlight dimming circuit for supplying a luminance dimming voltage to a backlight driving circuit of a liquid crystal display device having a backlight, and detects the ambient brightness on the surface side of the liquid crystal display panel. A plurality of optical sensors for outputting an external light illuminance signal, an average value calculating means for calculating an average value of all or part of the external light illuminance signals output from these optical sensors, and the average value calculating means A liquid crystal display comprising: a brightness adjusting unit that adjusts the brightness of the backlight driving circuit based on the calculated average value of the illuminance of the outside light and a light control setting amount that is manually set An apparatus backlight dimming circuit is disclosed.
JP-A-4-174819 Japanese Patent Laid-Open No. 9-146073

  According to the inventions described in the above-mentioned patent documents, the display luminance can be adjusted according to the illuminance of outside light, and for example, power consumption can be suppressed in a mobile phone, a PDA, or the like. However, the above-described conventional technology adopts a configuration in which a discrete light control sensor separate from the liquid crystal display panel is installed, which hinders downsizing and thinning of the liquid crystal display device. In mobile phones, PDAs, and the like, demands for miniaturization and thinning are strict, and hindering the miniaturization and thinning is a serious problem.

  In order to solve this problem, for example, it is conceivable to integrally form the optical sensor on one substrate (for example, an array substrate) of the liquid crystal display panel using a low-temperature polysilicon technology. The optical sensor integrally formed on the substrate has a problem that the characteristics change depending on the ambient temperature. The current flowing through the optical sensor includes a thermal current that increases or decreases depending on temperature, in addition to a photocurrent proportional to incident light. For this reason, for example, even if an output equivalent to 500 lux is obtained from an optical sensor, it can be accurately distinguished whether it is really 500 lux or a result of a large amount of photocurrent due to high temperature even though it is 300 lux. difficult. Therefore, there is a problem that the dimming performance varies depending on the ambient temperature.

  The present invention has been proposed in view of such a conventional situation, and can cope with downsizing and thinning, and can accurately calculate illuminance regardless of temperature and appropriately brightness (for example, backlight). An object is to provide a display device capable of controlling the amount of light.

  In order to achieve the above-described object, a display device according to the present invention includes an array substrate on which a drive circuit is formed, and in a display device having a predetermined display area, an optical sensor that measures external light illuminance on the array substrate. Is installed, and a temperature sensor is installed. Also, the display device control method of the present invention is a display device control method including an array substrate on which a drive circuit is formed and having a predetermined display area, and is controlled by an optical sensor installed on the array substrate. The light intensity is measured, the output of the optical sensor is corrected based on the output of the temperature sensor, and the brightness of the display area is adjusted.

  In the display device of the present invention, the ambient light illuminance is measured by the optical sensor. In this case, for example, if the first optical sensor is integrally formed on the array substrate by low-temperature polysilicon technology or the like, it is advantageous in terms of downsizing and thinning. However, from the optical sensor integrally formed by low-temperature polysilicon technology or the like, The output includes a thermal current that increases or decreases depending on the temperature, and it is difficult to accurately determine the illuminance of outside light.

  Therefore, in the present invention, in addition to the optical sensor, a temperature sensor that measures the ambient temperature of the optical sensor is installed, and the measured value of the optical sensor is corrected based on the output from the temperature sensor. The temperature sensor measures the thermal current that increases or decreases with temperature, and subtracting the thermal current required from the output of the temperature sensor from the output of the optical sensor extracts only the output from the external light, and the external light illuminance is accurate. Is measured.

  According to the present invention, it is possible to provide a display device that can be reduced in size and thickness and that can accurately calculate illuminance. Therefore, for example, it is possible to appropriately control the luminance by appropriately adjusting the backlight, and it is possible to realize a display device that has excellent visibility and low power consumption in any environment.

  Hereinafter, a display device (here, a liquid crystal display device) to which the present invention is applied will be described in detail with reference to the drawings.

  FIG. 1 shows an example of a liquid crystal display device. In the liquid crystal display device 1, a liquid crystal cell is formed by a pair of light-transmitting insulating substrates, and a liquid crystal material is sealed in a gap between them to form a liquid crystal layer. Specifically, a liquid crystal layer 4 is sealed between the array substrate 2 and the counter substrate 3.

  The array substrate 2 uses, for example, a light-transmissive insulating substrate made of glass or the like as a support substrate. On the light-transmissive insulating substrate, scanning lines arranged substantially parallel to each other at equal intervals, or substantially orthogonal to these scanning lines. Signal lines arranged in layers, an interlayer insulating film (transparent insulating film) that is interposed between the scanning lines and the signal lines to electrically insulate them, and a switching element disposed near the intersection of the scanning lines and the signal lines Thin film transistors (TFTs) are formed.

  In the array substrate 2, pixel electrodes electrically connected to the switching elements through through holes formed in the interlayer insulating film are arranged in a matrix. Note that, as described above, signal lines, scanning lines, switching elements such as thin film transistors, interlayer insulating films, and the like are disposed between the light-transmissive insulating substrate of the array substrate 2 and the pixel electrodes. These illustrations are omitted. Further, an alignment film is provided on almost the entire surface of the array substrate 2 on which the pixel electrodes are provided. This is also omitted here.

  On the other hand, the counter substrate 3 also has a light-transmitting insulating substrate made of glass or the like as a support substrate, and a color filter layer 5 is formed on the surface on the liquid crystal layer 4 side corresponding to each pixel. In addition, a transparent counter electrode 6 made of a transparent conductive material such as ITO is formed on the entire surface so as to cover the surface. The color filter layer is a resin layer colored in colors by pigments or dyes, and is configured by combining filter layers of R, G, B colors, for example. Although not shown, a so-called black matrix layer is formed at the pixel boundary portion of each color filter layer for the purpose of improving the contrast.

  In the liquid crystal display device 1 having the above configuration, polarizing plates 7 and 8 are provided outside the array substrate 2 and the counter substrate 3, respectively, and an image display is performed using a backlight 9 disposed on the back side as a light source. Is done.

  FIG. 2 is a schematic plan view of the liquid crystal display device 1. A black matrix BM is formed in a frame shape outside the display area A which is an active area where image display is performed, and the light of the backlight 9 is displayed. Is configured not to leak. Then, outside the area where the black matrix BM is formed, the external LSI 10 is mounted on the array substrate 2 by chip-on-glass (COG).

  The basic configuration of the liquid crystal display device 1 has been described above. In the liquid crystal display device 1 of the present embodiment, the opening 11 is provided in the black matrix BM outside the display region A, and the array substrate faces the surface. 2 is provided with an external light illuminance measuring optical sensor 12. Further, a temperature sensor 13 for measuring the ambient temperature of the external light illuminance measuring optical sensor 12 is installed on the array substrate 2 similarly in the vicinity of the external light illuminance measuring optical sensor 12.

  FIG. 3 shows an installation state of the external light illuminance measuring optical sensor 12 and the temperature sensor 13. As described above, the external light illuminance measurement optical sensor 12 is provided so as to face a portion (opening 11) where the black matrix BM of the counter substrate 3 is not present, and the external light is transmitted from the opening 11 to the liquid crystal display device 1. And enters the external light illuminance measurement optical sensor 12. A light shielding layer 14 is provided under the external light illuminance measurement optical sensor 12 so that light from the backlight 9 does not directly strike the external light illuminance measurement optical sensor 12.

  The temperature sensor 13 is disposed in the vicinity of the external light illuminance measurement optical sensor 12 and is installed in an environment equivalent to the external light illuminance measurement optical sensor 12. As a result, the temperature of the temperature sensor 13 and the temperature of the external light illuminance measurement optical sensor 12 become substantially the same, and the temperature compensation of the external light illuminance measurement optical sensor 12 becomes possible.

  Both the external light illuminance measuring optical sensor 12 and the temperature sensor 13 are integrally formed on the array substrate 2. For example, as with the thin film transistors on the array substrate 2, for example, using a low-temperature polysilicon technique, Is formed.

  4 shows a configuration example of a thin film transistor and an optical sensor formed on the array substrate 2, FIG. 4 (a) shows a configuration of an n-channel thin film transistor, FIG. 4 (b) shows a configuration of a p-channel thin film transistor, FIG. 4C shows a configuration of a PIN diode used as an optical sensor.

  As shown in FIGS. 4A and 4B, the thin film transistors (n-channel thin film transistors and p-channel thin film transistors) are polycrystalline semiconductor layers (polysilicon layers) on a substrate 21 via an undercoat layer 22. 23A and 23B are formed, and the polycrystalline semiconductor layers 23A and 23B are used as channel layers.

  As described above, the undercoat layer 22 is formed on the substrate 21. The undercoat layer 22 is flattened by closing scratches or holes on the surface of the substrate 21, and the polycrystalline semiconductor layer 23A of impurities contained in the substrate 21. , 23B for the purpose of preventing diffusion. The undercoat layer 22 is formed by forming a silicon oxide film, a silicon nitride film, or the like. For example, the undercoat layer 22 includes a planarizing layer made of a fluidized resin that is fluidized by heat treatment, and a coating that prevents diffusion of impurities. It is also possible to have a laminated structure composed of layers. Alternatively, when the substrate 21 is excellent in planarization and contains a small amount of impurities, the undercoat layer 22 can be omitted.

  The polycrystalline semiconductor layers 23A and 23B formed on the undercoat layer 22 are polycrystallized by laser irradiation or the like after annealing amorphous silicon (a-Si) formed by, for example, a plasma CVD method. It is formed by this. The polycrystalline semiconductor layers 23A and 23B are separated into islands by etching and arranged in a matrix.

  The polycrystalline semiconductor layer 23A corresponds to an n-channel thin film transistor, and the polycrystalline semiconductor layer 23B corresponds to a p-channel thin film transistor. Accordingly, source regions 23Aa and 23Ba and drain regions 23Ab and 23Bb are formed in the polycrystalline semiconductor layers 23A and 23B by impurity implantation. Furthermore, in an n-channel thin film transistor, an LDD region (low-concentration impurity diffusion region) is formed. 23Ac and 23Ad are formed.

  In any thin film transistor, a first metal (gate electrode) 26 and a second metal 27 are formed on the polycrystalline semiconductor layers 23A and 23B via a first insulating layer 24 and a second insulating layer 25. .

On the other hand, in the PIN diode, as shown in FIG. 4C, the light shielding pattern 28 is formed on the substrate 21 using a metal material (for example, Mo—W alloy). The light shielding pattern 28 is connected to a power supply line (not shown) through a through hole (not shown), and is set to a specific potential (for example, a GND level) at least in the sensor unit. In addition, the PIN diode is made of SiN _x , SiO _x, or the like in the same manner as the previous thin film transistor in order to prevent diffusion of impurities from the light shielding pattern 28 and the substrate 21 into an element (PIN diode) formed on the substrate 21. An undercoat layer 22 is provided.

  The light shielding pattern 28 does not have to be provided under each thin film transistor. When the light shielding pattern 28 is not provided in these thin film transistors, there is an advantage that the aperture ratio is improved. Further, when the light-shielding pattern 28 is provided under the thin film transistor, there is an advantage that the image quality is improved, for example, the off-leak current of the thin film transistor can be reduced and the contrast ratio is improved.

On the undercoat layer 22, as in the thin film transistor, a polycrystalline semiconductor layer 23C is formed simultaneously with the polycrystalline semiconductor layers 23A and 23B, and p ⁺ region 23Ca, p ⁻ region 23Cb, n ⁻ region 23Cc and n ^+. Region 23Cd is formed. In this way, a diode is formed by forming p ⁺ / p ⁻ / n ⁻ / n ⁺ in the horizontal direction, and the irradiation light intensity when the p ⁺ side is GND (0 V) and the n ⁺ side is 5 V. A photocurrent corresponding to the current flows through both ends of the diode.

The PIN diode may be configured without the n ⁻ region 23Cc. Further, as shown in FIG. 4C, instead of forming each region in the horizontal direction and forming the PIN diode, the PIN diode may be configured by stacking these regions in the vertical direction. Also in the PIN diode, the first metal 26 and the second metal 27 are formed on the polycrystalline semiconductor layer 23C via the first insulating layer 24 and the second insulating layer 25 as in the case of the thin film transistor. It is.

  On the other hand, the temperature sensor 13 uses a resistance element formed of, for example, polysilicon as a thermal element. The resistance of polysilicon depends on temperature. For example, as shown in FIG. 5, the resistance value decreases as the temperature increases, and conversely, the resistance value tends to increase as the temperature decreases. This property is used for the temperature sensor 13.

  As the structure of the resistance element, as shown in FIGS. 6A and 6B, it is only necessary to form electrodes 32 and 33 on both ends of the resistor 31 made of polysilicon. When considering simultaneous formation with the photosensor (PIN diode) 12, the resistor 31 is formed on the array substrate 2, and the first insulating layer 24 and the second insulating layer 25 are formed. The electrodes 32 and 33 are formed by forming openings in the insulating layer 24 and the second insulating layer 25.

In the resistance element having the above structure, the temperature dependence of the resistance value of the resistor 31 varies depending on the type and concentration of impurities implanted into the polysilicon. In this case, if the types and concentrations of impurities used for the n-channel thin film transistor and the p-channel thin film transistor are applied, the resistor (polysilicon) 31 into which impurities are implanted can be formed at the same time in the process of forming the transistor. Is possible. In this case, the resistor 31, p ^- region, p ⁺ region, n ^- region, but will be formed either as n ⁺ regions. Among them, n in terms of characteristics such as ^- the region It is preferable. In the resistance element, the region 31a which serves as a heat sensitive element of the resistor 31 n ^- and regions, and the end portions 31b and n ⁺ regions. For both end portions 31b to which the electrodes 32 and 33 are connected, it is preferable to lower the resistance value as much as possible as an n ⁺ region.

  Whereas the current value of the optical sensor (PIN diode) 12 and the thin film transistor described above has dependency on both light and heat, the resistance element having the above structure has almost no dependency on light, and the resistance value is light. Therefore, it functions as a temperature sensor having only thermal dependence.

  Next, a method for measuring the external light illuminance in the liquid crystal display device 1 having the above-described configuration will be described. First, FIG. 7 shows a circuit block of an optical sensor circuit. As described above, on the array substrate 2, for example, pixel TFTs for display, a gate line driving circuit, a signal line driving circuit, and the like using low-temperature polysilicon technology, the optical sensors 51, the amplifier (AMP) 52, An A / D conversion circuit 53 is integrally formed. The external LSI 10 is provided with an illuminance calculation circuit and a control signal generation circuit 54 connected to the sensor circuit.

  FIG. 8 is a circuit diagram of an optical sensor circuit formed on the array substrate 2. The optical sensor circuit includes a photodiode (each optical sensor) 55 and a capacitor element 56. A predetermined voltage Vprc is precharged in the capacitor element 56 at a predetermined timing, and a photocurrent corresponding to the external light illuminance flows through the photodiode 55.

  FIG. 9 shows how the voltage of the capacitor element 56 changes with time. For example, when external light is applied to the external light illuminance measurement optical sensor 12, a current flows through the photodiode 55 (external light illuminance measurement optical sensor 12), and therefore gradually decreases from the initial precharge voltage Vprc toward the GND voltage. I will do it. This is converted into a digital signal by an A / D conversion circuit 53 formed on the array substrate 2 at a predetermined timing. Then, it is output to the external LSI 10 at a predetermined timing. If the absolute value of the slope in FIG. 8 is large, it can be considered that the external light illuminance is strong, and if the absolute value of the slope is small, the external light illuminance is weak.

  Here, the A / D conversion circuit 53 is not particularly limited. For example, a circuit that applies a reference voltage Vtp in steps from an external IC and compares it with the output voltage of the sensor can be used. An example of the A / D conversion circuit 53 is shown in FIG.

  The A / D conversion circuit 53 includes three switches SW1, SW2, and SW3, a capacitor element 61, and an inverter 62. As shown in FIG. 10A, when SW1 = H and SW2 = L, the sensor output voltage Vs is charged at the node n1 and the operation threshold value of the inverter is charged at the node n2. On the other hand, as shown in FIG. 10B, when SW1 = L and SW2 = H, a comparison operation of the sensor output voltages Vs and Vtp is performed, and different Vout logic outputs depending on whether or not Vs is greater than Vtp. can get. Each time the sensor output is sampled, the value of Vs can be obtained by changing Vtp stepwise. At this time, the finer the step of Vtp, the higher the accuracy.

  In the optical sensor circuit, the time until the output of the A / D conversion circuit 53 is inverted (that is, the time until the potential of the capacitor element 56 is reduced by ΔV = 2.5 V due to leakage) ΔT is measured, and from this time ΔT The current I flowing through the photodiode 55 (external light illuminance measurement optical sensor 12) can be calculated as I = dQ / dt = CΔV / ΔT. The precharge voltage Vprc is 5 V, for example, and the reference voltage Vtp is 2.5 V, for example.

  The external light illuminance is calculated based on the output of the external light illuminance measurement optical sensor 12 as described above, but accurate measurement alone is difficult. This is because the external light illuminance measurement optical sensor 12 formed on the array substrate 2 is affected by a thermal current that increases or decreases depending on the temperature. Therefore, in the liquid crystal display device 1 of the present embodiment, the temperature sensor 13 is provided as described above in addition to the external light illuminance measurement optical sensor 12, and the temperature dependence of the external light illuminance measurement optical sensor 12 using the output is provided. Is removed, and the influence is eliminated.

  As shown in FIG. 11, the temperature sensor circuit includes a temperature sensor 71, an A / D conversion circuit 73, and a control signal generation circuit 74, similar to the optical sensor circuit. The configuration of the A / D conversion circuit 73 is the same as that of the A / D conversion circuit 53 of the optical sensor circuit.

  FIG. 12 is a circuit diagram of a temperature sensor circuit formed on the array substrate 2. The temperature sensor circuit includes a resistance element 75 and a capacitor element 76. A predetermined voltage Vprc is precharged to the capacitor element 76 at a predetermined timing, and a current corresponding to a change in resistance value due to a temperature change of the resistor constituting the resistance element 75 flows through the resistance element 75.

  The temperature sensor circuit measures ΔT ′ until the output of the A / D conversion circuit 73 is inverted (that is, the time until the potential of the capacitor element 76 is reduced by ΔV ′ = 2.5 V due to leakage). The current I flowing through the resistance element 75 from this time ΔT ′ can be calculated as I ′ = dQ ′ / dt = CΔV ′ / ΔT ′. The precharge voltage Vprc is 5 V, for example, and the reference voltage Vtp is 2.5 V, for example.

  In the optical sensor circuit and the temperature sensor circuit described above, the same circuit can be used for the A / D conversion circuits 53 and 73. Also, the precharge timing can be shared. Therefore, the control signal can be shared by the common use, and the area occupied by the frame portion of the display device incorporating these circuits can be reduced.

  Specifically, the temperature correction is performed as follows. The temperature correction is performed by an external IC. For example, an external IC that performs temperature correction may be disposed on the frame portion of the array substrate 2.

  For example, the current flowing through the optical sensor 12 (photocurrent + thermal current) is 5 pA at 25 ° C. and 100 lux. As shown in FIG. 13, the thermal current is 2 pA at 25 ° C., 4 pA doubled at 50 ° C., and 1 pA 0.5 times at −20 ° C. In the meantime, it is almost straight-line approximation and there is no practical problem. On the other hand, the current of the resistance element 75 is 108% at 50 ° C. and 88% at −20 ° C. with respect to 25 ° C., as shown in FIG. Between these, there is no problem in practical use because it is almost linear approximation. Therefore, for example, if the current of the resistance element 75 is 104% from the A / D conversion output 73 of the temperature sensor 71 after a predetermined time has elapsed, the temperature is calculated to be 37.5 ° C. by proportional calculation. At this time, the thermal current of the optical sensor 51 is considered to be 3 pA, which is 1.5 times larger than the value at 25 ° C. Therefore, the A / D conversion output of the optical sensor 51 reduces the contribution of the thermal current 3 pA. Data for dimming without the influence of temperature characteristics can be obtained. It goes without saying that the same correction can be made even if the temperature characteristics of the optical sensor 51 and the resistive element 75 are more complicated than those described above. In addition, although the example used for correction | amendment of a light control sensor was shown here, it can also be used for the operating point correction | amendment etc. of an optical touch panel etc., for example.

  As described above, in the liquid crystal display device 1 of the present embodiment, the optical sensor and the temperature sensor are integrally formed on the array substrate 2, so that the size and thickness can be reduced, and accurate illuminance calculation is possible. It is. In addition, since the temperature sensor and its signal conversion circuit are integrally formed on the array substrate and a temperature correction function is provided, for example, the ambient temperature changes and the photocurrent value changes with respect to the value at normal temperature. However, it is possible to appropriately correct this by looking at the output of the temperature sensor. Therefore, it is possible to realize a liquid crystal display device that is appropriately adjusted in the backlight and has excellent visibility in all temperature environments and low power consumption.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.

  For example, as described above, the array substrate 2 is provided with the ambient light illuminance measurement sensor 12 and the temperature sensor 13, and in addition to the ambient light illuminance measurement optical sensor 12, the second and third sensors are used. It is also possible to install an optical sensor on the array substrate 2.

  FIG. 15 shows a specific example of the second and third photosensors. For example, as the second optical sensor, a backlight illuminance measurement optical sensor 41 as shown in FIG. The backlight illuminance measurement optical sensor 41 is provided to monitor the illuminance of the backlight 9, and as shown in FIG. 15A, the backlight illuminance measurement optical sensor 41 is provided on the light shielding layer 14 below the backlight illuminance measurement optical sensor 41. Is provided with an opening 14a for taking in the light of the backlight 9. Note that the light shielding layer 14 may be omitted instead of forming the opening 14a. The black matrix BM on the counter substrate 3 side is not provided with an opening, and therefore, the backlight illuminance measurement optical sensor 41 is not directly irradiated with external light. In addition, light directly enters the backlight illuminance measurement optical sensor 41 from the backlight 9 disposed in the vicinity, and the incident light intensity is higher than that of external light. The light receiving area is smaller than that of the external light illuminance measuring optical sensor 12, and is preferably 1 / P (P> 1), for example.

  FIG. 15B is a configuration example of the third photosensor. As a 3rd optical sensor, the total illumination intensity measurement sensor 42 which measures all the lights (external light and the light of the backlight 9) can be mentioned, for example. In this total illuminance measurement sensor 42, the opening 11 is formed in the black matrix BM on the counter substrate 3 side so that external light can be taken in, and the backlight 9 is provided on the light shielding layer 14 below the total illuminance measurement optical sensor 42. An opening 14a is provided for taking in the light. Also in this case, the light shielding layer 14 can be omitted instead of forming the opening 14a.

  By providing the backlight illuminance measurement optical sensor 41 and the total illuminance measurement sensor 42, the ambient light illuminance is converted based on the external light illuminance measurement optical sensor 12 based on these outputs, or the illuminance fluctuation of the backlight 9. Can be used to adjust the light amount of the backlight 9.

  Further, for example, at least one external light illuminance measurement optical sensor 12 may be installed. For example, a plurality of external light illuminance measurement optical sensors 12 having different light receiving areas are installed, and these external light illuminances are set according to the external light illuminance. It is also possible to measure the illuminance by switching the measurement optical sensor 12.

  Specifically, for example, as shown in FIG. 16, 16 types of optical sensors P1, P2,..., P16 having different sensitivities are provided as external light illuminance measuring optical sensors. Here, the optical sensor P1 is a high-sensitivity optical sensor, the optical sensor P16 is a low-sensitivity sensor, and the optical sensors P2 to P15 in the meantime gradually change the sensitivity. When a plurality of photosensors having different sensitivities are provided as described above, for example, as shown in FIG. 17, the output of the photosensor P1 is too sensitive to obtain the illuminance correctly, while the output of the photosensor P16 is Even in the case where the illuminance cannot be obtained correctly because the sensitivity is too low, the illuminance can be obtained using the output if the sensitivity of the optical sensor P5, for example, is appropriate.

  18 and 19 show specific examples for extracting the outputs of a plurality of optical sensors. FIG. 18 is a time sequence. Starting from the frame in which the signal ZST defining the frame to be read becomes high level, the outputs of 16 types of photosensors are sequentially output over a total of 16 frames. FIG. 19 shows an example of a circuit provided on the array substrate. A 4-bit counter 81 and a sensor selection circuit 82 are provided on the array substrate. The ZST is input to the 4-bit counter 81, and when ZST is input to the 4-bit counter 81, the count is incremented by one count. Based on the 16 outputs of the 4-bit counter 81, one of the 16 types of photosensors P1 to P16 is selected. In the frame, the output of the selected photosensor is supplied to the outside and used for illuminance calculation. Externally, the outputs of 16 types of optical sensors are accumulated, and a predetermined calculation is performed to determine an appropriate illuminance value. ZST is issued by the CPU and supplied onto the array substrate via the driver IC. The counter may be a 16-stage shift register array. ZST may be input to the first stage, a shift pulse is sent to the next stage every frame period, and one of 16 types of photosensors may be selected based on the shift pulse of each stage. Alternatively, as another method that does not require ZST, the 4-bit counter 81 is reset when the power is turned on, and thereafter, the number of frames is simply counted, and the corresponding type of optical sensor is always output based on the state of the 4-bit counter 81. The sensor selection circuit 82 may be configured as described above. This has the advantage that ZST need not be supplied from the outside.

  Further, the external light measurement optical sensor 12 formed on the array substrate also has local variations. This local variation causes the illuminance calculation to go wrong. This countermeasure is shown in FIGS. 20 and 21 show configuration examples for smoothing local variations of the optical sensor. In this example, N photosensors P1 to PN having the same sensitivity are simultaneously precharged and simultaneously exposed to external light. By short-circuiting each other when sampling to the amplifier 52, even if the characteristics (outputs S1 to SN) of the optical sensors P1 to PN vary locally as shown in FIG. Then, the illuminance can be obtained with higher accuracy by performing the above-described processing for obtaining the illuminance by performing A / D conversion or the like.

  That is, assuming that the voltages of the capacitors immediately before sampling by the amplifier 52 are V1, V2,... VN, the amplifier input voltage Vin after the switches S1, S2,. As a result, the average value is calculated. Various calculations such as weighting are possible. As described above, outputting only the result calculated on the array substrate has an advantage that the number of output pins can be reduced as compared with the case of outputting the values of N photosensors.

  Furthermore, a color filter can be formed in the opening 11 of the black matrix BM corresponding to the external light illuminance measurement optical sensor 12. As described above, when the external light illuminance measurement optical sensor 12 is built in the array substrate 2 and the brightness of the backlight is adjusted using this output, the light of the external light illuminance measurement optical sensor 12 becomes a problem. That is, the sensitivity to the wavelength of the human eye does not necessarily match the wavelength characteristic of the human eye. This has a problem that, for example, when the infrared or ultraviolet region is strong, the output of the external light illuminance measurement optical sensor 12 appears to be bright even in a dark environment for human eyes. For example, when there is a heating appliance that emits infrared rays in a dark room, the infrared sensor illuminance measurement light sensor 12 outputs a large amount by sensing the infrared rays, and the backlight brightness is increased more than necessary. Malfunctions occur. Therefore, by forming a color filter at the place where the external light illuminance measuring optical sensor 12 is disposed, the infrared or ultraviolet light is attenuated, and light having a wavelength that is perceived by human eyes is selectively entered into the photosensor. By doing so, this problem can be improved.

  When forming the color filter, it is desirable for the human eye to form a green color filter because there is a sensitivity peak at the green wavelength. In addition, the blue color filter can easily transmit ultraviolet rays, but generally, a polarizing plate used in a liquid crystal display element contains an ultraviolet filter, so that the blue filter can be effective for the above purpose. In addition, although the additive color mixture of three primary colors of red, green and blue is used here, the same effect can be obtained even in the case of a subtractive color filter. In that case, a cyan color is suitable.

  When forming the color filter, as shown in FIG. 23, the light sensor PT without the color filter, the light sensor PR with the red color filter, the light sensor PG with the green color filter, and the light with the blue color filter. By providing sensors PB at a predetermined ratio and shorting these optical sensors together before sampling by the amplifier 52, it is possible to freely set a correction suitable for the application of the display (environmental light that can be exposed). is there. As a modified example, a photosensor PT without a color filter, a photosensor PR with a red color filter, a photosensor PG with a green color filter, and a photosensor PB with a blue color filter are provided at an equal ratio. For the time being, all the sensor outputs may be handed over to the CPU, and averaging processing may be performed while weighting. The color filter can be formed simultaneously with the color filter in the display area.

  24 and 25 show a system configuration particularly suitable for achieving both narrowing of the frame of a display device (for example, a liquid crystal cell) and high-precision light control. In the case of this example, the A / D conversion circuit 53 is incorporated in the LSI 10, and the control signal generation circuit 54 is incorporated in the CPU 81 provided outside. Further, the output of the control signal generation circuit 54 is input to the backlight controller 82 to control the amount of light of the backlight 9. When displaying an image, image data 91 is sent from the CPU 81 to the A / D conversion circuit 92 of the LSI 10, and further, the switching elements (thin film transistors) of the pixels 94 are driven via the amplifiers 93 on the array substrate 2.

  In the case of this example, the A / D conversion circuit 53 is not formed on the array substrate 2. This is because the circuit on the array substrate 2 has poorer transistor characteristics than the circuit formed on the silicon wafer, so that the error becomes large. It is more advantageous in terms of accuracy to digitize the output of the amplifier 52 on the array substrate 2 by the A / D conversion circuit 53 provided in the source driver (LSI 10) than when digitizing on the array substrate 2. . It is better not to perform complex illuminance calculations in the source driver. In order to perform complicated calculations with the source driver, a logic circuit must be formed in the source driver to some extent. As a result, the area of the source driver is increased, and the frame area of the lower side of the liquid crystal display cell is increased. Since the CPU 81 uses the finest process in the system, even if complicated illuminance calculation is performed, the influence on the outer shape of the set is small. The CPU 81 may have a temperature sensor (can be used for correction).

  Although the liquid crystal display device has been described above as an example, the present invention is also effective for a light emitting display device such as an organic EL display. Controlling the light emission luminance of the organic EL element by detecting the illuminance of outside light is effective for reducing power consumption in a dark place and improving visibility in a bright place.

It is a schematic sectional drawing which shows typically an example of the liquid crystal display device to which this invention is applied. It is a schematic plan view which shows typically an example of the liquid crystal display device to which this invention is applied. It is a schematic sectional drawing which expands and shows the installation part of an optical sensor and a temperature sensor. (A) is a schematic sectional view of an n-channel thin film transistor, (b) is a schematic sectional view of a p-channel thin film transistor, and (c) is a schematic sectional view of a PIN diode (photosensor). It is a characteristic view which shows the temperature dependence of the resistance value of a polysilicon. The structural example of a resistive element is shown, (a) is a schematic plan view, (b) is a schematic sectional drawing. It is a circuit diagram which shows an example of an optical sensor circuit. It is a circuit diagram of an optical sensor. In an optical sensor, it is a figure which shows a mode that the voltage (amplifier output) of a capacitor element changes with time. It is a circuit diagram which shows an example of an A / D conversion circuit, (a) shows the case where Vs> Vtp, and (b) shows the case where Vs <Vtp. It is a circuit diagram which shows an example of a temperature sensor circuit. It is a circuit diagram of a temperature sensor. It is a characteristic view which shows the temperature dependence of the electric current which flows into an optical sensor. It is a characteristic view which shows the temperature dependence of the resistance value (relative value) of a temperature sensor. It is a schematic sectional drawing which expands and shows the installation part of an optical sensor, (a) shows the installation state of the optical sensor for backlight illumination intensity measurement, (b) shows the installation state of the optical sensor for total illumination intensity measurement. It is a circuit diagram which shows an example of the sensor circuit at the time of providing the some optical sensor from which a sensitivity differs. It is a figure which shows the mode of the time-dependent change of the amplifier output in each optical sensor at the time of providing the several optical sensor from which a sensitivity differs. It is a figure which shows an example of the time sequence in the case of taking out the output of a some optical sensor. It is a figure which shows an example of the circuit provided on the array board | substrate in the case of taking out the output of a several photosensor. It is a figure which shows the structural example for smoothing the local dispersion | variation of an optical sensor. It is a circuit diagram of each optical sensor in the structure for smoothing the local dispersion | variation of an optical sensor. It is a figure which shows a mode that the local dispersion | variation of an optical sensor is smoothed. It is a circuit diagram showing an example of a sensor circuit which has a plurality of photosensors provided with various color filters. It is a top view which shows schematic structure of the display apparatus suitable for making narrow frame and high-precision light control compatible. It is a figure which shows the system configuration suitable for making narrow frame and high-precision light control compatible.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device, 2 Array board | substrate, 3 Opposite board | substrate, 4 Liquid crystal layer, 11 Opening part, 12 Photosensor (photosensor) for external light illuminance measurement, 13 Temperature sensor, 4,15 Light shielding layer, 31 Resistor, 31a n ⁻ Area, 31b n ⁺ area, 32, 33 electrodes, 41 light sensor for backlight illuminance measurement, 42 light sensor for total illuminance measurement

Claims (10)

In a display device that includes an array substrate on which a drive circuit is formed and has a predetermined display area,
An optical sensor for measuring the illuminance of external light is installed on the array substrate, and a temperature sensor is installed.   The display device according to claim 1, wherein the temperature sensor includes a resistance element formed using polysilicon as a temperature-sensitive element.   The display device according to claim 2, wherein an impurity is implanted into the polysilicon constituting the resistance element.   4. The display device according to claim 3, wherein the polysilicon constituting the resistance element is made n-type by implantation of the impurities.   A capacitor element is connected to the resistance element to form a temperature sensor circuit, and a temperature is detected based on a voltage change amount after a predetermined time has elapsed by applying a precharge voltage to one terminal of the capacitor element at a predetermined cycle. The display device according to claim 2, wherein the display device is a display device.   An integrated circuit element for processing an output signal output from the optical sensor is installed on the array substrate, and the integrated circuit element corrects the output signal of the optical sensor based on the output of the temperature sensor. The display device according to claim 1. The outputs of the optical sensor and the temperature sensor are respectively input to the integrated circuit element through an A / D conversion circuit that converts an output signal into a digital signal and outputs the digital signal to the integrated circuit.
7. The display device according to claim 6, wherein the A / D conversion circuit of the optical sensor and the A / D conversion circuit of the temperature sensor have the same format and are controlled by the same control signal. A liquid crystal display device comprising a counter substrate facing the array substrate, wherein a liquid crystal layer is sandwiched between the substrates to form a display region;
The display device according to claim 1, further comprising a backlight.   The display device according to claim 1, wherein brightness adjustment of the display area is performed based on illuminance of outside light detected by the optical sensor. A method for controlling a display device including an array substrate on which a drive circuit is formed and having a predetermined display area,
Control of a display device characterized in that external light illuminance is measured by a photosensor installed on the array substrate, the output of the photosensor is corrected based on the output of the temperature sensor, and the brightness of the display area is adjusted. Method.

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