JP3716651B2 - Display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a display device including a non-light emitting display panel such as a liquid crystal display panel.
[0002]
[Prior art]
For example, a display device having a non-light-emitting display panel such as a liquid crystal display panel can be roughly classified into a transmission type that displays using transmitted light and a reflection type that displays using reflected light. However, there is also a reflection / transmission type that combines the two. In the case of a reflection / transmission type display device, although not shown, generally, a transflective plate is disposed on the back side of a non-luminous display panel, and a backlight is disposed on the back side. It has a structure. And when using it as a transmissive type, the backlight is turned on, the light from the backlight is transmitted through the semi-transmissive semi-reflective plate and the display panel and emitted to the surface side of the display panel, thereby performing display. Yes. On the other hand, when used as a reflective type, the backlight is not turned on, and external light incident from the surface side of the display panel is transmitted through the display panel and reflected by the semi-transmissive semi-reflective plate, and this reflected light is displayed. The panel is transmitted and emitted to the surface side of the display panel, thereby performing display.
[0003]
[Problems to be solved by the invention]
By the way, in such a display device, it is possible to perform display using both external light and light from the backlight simultaneously. In this case, the illuminance of the external light is detected by the external light illuminance detection sensor, the illuminance of the light from the backlight is detected by the backlight illuminance detection sensor, and the luminance of the light from the backlight is determined based on these detection results. By controlling, it is conceivable that the screen brightness of the display panel by both the external light and the light from the backlight becomes a suitable screen brightness according to the illuminance of the external light. However, for example, when a chip component in which a phototransistor or a photodiode is formed on a silicon chip is used as the illuminance detection sensor, the number of components increases.
An object of the present invention is to prevent the number of parts from increasing even if an illuminance detection sensor is provided.
[0004]
[Means for Solving the Problems]
The present invention is a display device capable of performing display by using both light from a backlight and external light simultaneously disposed on the back side of a non-light emitting display panel having a pair of opposing substrates. An external light illuminance detection sensor that is integrally formed with the display panel and detects the illuminance of external light, and a backlight illuminance that is integrally formed with the display panel and detects the illuminance of light from the backlight. A detection sensor; and backlight luminance control means for controlling luminance of light from the backlight based on a detection result by the external light illuminance detection sensor and a detection result by the backlight illuminance detection sensor, and the external light illuminance detection sensor and the backlight illumination detection sensor is integrally formed on the front surface of the back side of the substrate of the display panel, the external light illuminance detecting sensor and before The backlight illuminance detection sensor includes a photoelectric conversion thin film transistor in which a first gate electrode made of a light-shielding material is arranged on the back surface side and a second gate electrode made of a light-transmissive material is arranged on the front surface side. Tei Te, the backlight illumination detection sensor which was characterized that you have been formed in a portion opposed to the reflective layer formed on the back surface of the substrate on the surface side of the display panel on the surface of the back side of the substrate is there. According to the present invention, since the external light illuminance detection sensor and the backlight illuminance detection sensor are integrally formed on the same surface of the display panel, the number of parts is prevented from increasing even if the illuminance detection sensor is provided. In addition, holes can be ejected from the trap level between the semiconductor layer and the top gate insulating film to be refreshed (reset).
[0005]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a main part of a reflection / transmission type liquid crystal display device to which an embodiment of the present invention is applied. This liquid crystal display device includes an active matrix liquid crystal display panel 1 having a switching element such as a thin film transistor between a data line and each pixel electrode. Although not shown in detail in the liquid crystal display panel 1, a pair of glass substrates 2 and 3 are bonded together via a substantially frame-shaped sealing material 4, and between the glass substrates 2 and 3 inside the sealing material 4. Liquid crystal is sealed, and polarizing plates 5 and 6 are attached to the surfaces of the glass substrates 2 and 3.
[0006]
A backlight 11 having a reflection function is disposed on the back side of the liquid crystal display panel 1. The backlight 11 includes an optical sheet 12 provided on the back surface of the liquid crystal display panel 1, a light diffusion layer 13 provided on the back surface of the optical sheet 12, and an optical member 14 provided on the back surface of the light diffusion layer 13. And a light guide 15 provided on the back side of the optical member 14 and a light source 16 provided on a predetermined one end face side of the light guide 15. The light source 16 includes a linear fluorescent tube 17 and a reflector 18 for reflecting the light from the fluorescent tube 17 toward one end surface of the light guide 15.
[0007]
As shown in FIG. 2, the light guide 15 is formed of an acrylic resin or the like, and the back surface is a flat surface, and a predetermined end surface perpendicular to the back surface is a light incident surface 21. Is a stepped structure that gradually becomes thinner from the light incident surface 21 side toward the other end surface side. In this case, the stepped surface is composed of a plurality of step surfaces 22 parallel to the back surface and step surfaces (light emitting surfaces) 23 perpendicular to these step surfaces 22. On each step surface 22, a reflection film 24 made of an aluminum vapor deposition film or the like is provided via a base film (not shown) made of silicon oxide. A reflective plate 25 is provided on the back surface of the light guide 15. And the light guide 15 is arrange | positioned in the back surface side of the liquid crystal display panel 1 in the state which inclined the back surface suitably with respect to the liquid crystal display panel 1. FIG.
[0008]
As shown in FIG. 2, the optical member 14 is formed of an acrylic resin or the like, and has a flat surface on the front surface, and a plurality of triangular projections 31 formed on the back surface at a constant pitch. It has a structured. In this case, the interface between one side surface of the projecting portion 31 and air is the first optical interface 32, and the interface between the other side surface of the projecting portion 31 and air is the second optical interface 33. The interface between the back surface of the optical member 14 and the air between the protrusions 31 is a third optical interface 34. The optical member 14 is disposed on the light guide 15 in a state where the apex of the protruding portion 31 is close to or in contact with the reflective film 24. In this state, the first optical interface 32 has an angle with respect to the step surface 22 of the light guide 15 (an angle on the side facing the step surface 23 of the first optical interface 32) of 90 ° or less, and the step surface The surface is substantially parallel to the surface 23 or an inclined surface close thereto. The second optical interface 33 is an inclined surface in which the angle with respect to the normal of the surface of the optical member 14 is larger than the angle formed by the normal and the first optical interface 32. The third optical interface 34 is a surface substantially parallel to the step surface 22 of the light guide 15 or an inclined surface close thereto. Note that the pitch of the protrusions 31 of the optical member 14 is substantially the same as the pixel pitch of the liquid crystal display panel 1 or is an integral fraction of the pixel pitch. Further, the pitch of the stepped surface 22 of the light guide 15 is slightly larger than the pitch of the protruding portions 31 of the optical member 14.
[0009]
The light diffusion layer 13 is made of, for example, a transparent adhesive in which light scattering fine particles are dispersed applied to the surface of the optical member 14. The optical sheet 12 is affixed to the surface of the optical member 14 via the light diffusion layer 13. The liquid crystal display panel 1 is attached to the surface of the optical sheet 12 through a transparent adhesive or a double-sided adhesive sheet 35. As shown in FIG. 3, the optical sheet 12 has a transmission axis P and a reflection axis S that are substantially orthogonal to each other, transmits light of a polarization component (P polarization component) along the transmission axis P, and passes through the reflection axis S. The light of the polarized component (S-polarized component) along is reflected. That is, when light including both the P-polarized component light along the transmission axis P and the S-polarized component light along the reflection axis S is incident from the back side of the optical sheet 12, Among them, the light of the P polarization component along the transmission axis P is transmitted through the optical sheet 12, and the light of the S polarization component along the reflection axis S is reflected by the optical sheet 12. Such a transflective characteristic is the same for incident light from the surface side of the optical sheet 12.
[0010]
Now, when this liquid crystal display device is used as a transmission type, the fluorescent tube 17 is turned on. Then, the light from the fluorescent tube 17 and the reflected light reflected by the reflector 18 enter the light incident surface 21 of the light guide 15. For example, as indicated by solid arrows in FIG. 2, the incident light travels in the light guide 15 in the lateral direction while being reflected by the reflective film 24 and the reflective plate 25, and from each step surface (light emitting surface) 23. Emitted. The emitted light is incident on the first optical interface 32 of the optical member 14, totally reflected by the second optical interface 33, and emitted from the surface of the optical member 14, as indicated by solid arrows in FIG. The light is incident on the light scattering layer 13 and scattered. Of this scattered light, the P-polarized component light is transmitted through the optical sheet 12 and incident on the back surface of the liquid crystal display panel 1, and the S-polarized component light is reflected by the optical sheet 12. However, the light reflected by the optical sheet 12 is reflected by the reflective film 24 and scattered again by the light scattering layer 13. Of this scattered light, the P-polarized component light is transmitted through the optical sheet 12 and incident on the back surface of the liquid crystal display panel 1, and the S-polarized component light is reflected by the optical sheet 12. Then, by repeating this, most of the light emitted from each step surface 23 is incident on the back surface of the liquid crystal display panel 1. The transmission axis of the optical sheet 12 and the transmission axis of the polarizing plate 6 on the back side of the liquid crystal display panel 1 are substantially parallel to each other. Then, the light incident on the back surface of the liquid crystal display panel 1 is transmitted through the liquid crystal display panel 1 and emitted to the front surface side of the liquid crystal display panel 1, thereby displaying.
[0011]
On the other hand, when this liquid crystal display device is used as a reflection type, the fluorescent tube 17 is not lit and external light is used. That is, external light (linearly polarized light) incident from the surface side of the liquid crystal display panel 1 passes through the liquid crystal display panel 1. For example, as shown by a dotted arrow in FIG. 2, this transmitted light is transmitted through the optical sheet 12, the light diffusion layer 13, and the optical member 14 in order, and is reflected by the reflective film 24. The reflected light passes through the optical member 14 and is diffused by the light diffusion layer 13. Most of the diffused light passes through the optical sheet 12 and enters the back surface of the liquid crystal display panel 1 in the same manner as described above. This incident light is transmitted through the liquid crystal display panel 1 and emitted to the front surface side of the liquid crystal display panel 1, whereby display is performed.
[0012]
Next, a description will be given of a case where the liquid crystal display device performs display using both the light from the light source 16 and external light simultaneously. By the way, the suitable screen brightness (the brightness at which the display can be observed with sufficient brightness under the use environment) of the liquid crystal display panel 1 varies depending on the illuminance of the use environment (hereinafter referred to as the environment illuminance). Depending on the ambient illuminance, the screen may be too bright or too dark. For example, in a use environment with high illuminance exceeding 100,000 lux, such as under direct sunlight in summer, it will be too bright.
[0013]
Therefore, in this liquid crystal display device, in order to obtain a suitable screen brightness that is not excessively dazzled even in a high illuminance usage environment exceeding 100,000 lux as in direct sunlight in summer, the liquid crystal display device mainly uses the reflective film 24. Reflectance of the entire device determined by the reflectance of external light and the light transmittance of the liquid crystal display panel 1 (the intensity of external light incident from the surface side of the liquid crystal display panel 1 and the liquid crystal display panel reflected by the reflective film 24 The ratio of the intensity of external light emitted to the surface side of 1 is set lower than that of a normal reflective liquid crystal display device using only external light.
[0014]
Further, by controlling the luminance of the light from the light source 16 according to the environmental illuminance or the like, the screen luminance of the liquid crystal display panel 1 due to both the light from the light source 16 and external light is suitable for the screen luminance according to the environmental illuminance. It is trying to become. That is, the liquid crystal display device includes light source luminance control means for controlling the luminance of light from the light source 16 in accordance with the ambient illuminance or the like. Next, the light source luminance control means will be described.
[0015]
First, FIG. 4 shows a schematic configuration of a part of the liquid crystal display device. Among the pair of glass substrates 2 and 3 of the liquid crystal display panel 1, a predetermined side portion of the glass substrate 3 on the back surface side protrudes from the glass substrate 2 on the front surface side. And the external light illumination intensity detection sensor 41 is provided in the upper surface of the protrusion part of the glass substrate 3 of this back surface side. Further, a backlight illuminance detection sensor 42 is provided at a predetermined portion of the upper surface of the glass substrate 3 on the back surface outside the sealing material 4 shown in FIG. In this case, a black mask 43 made of a metal such as chromium is provided on the lower surface of the glass substrate 2 on the front surface side, and external light is not incident on the backlight illuminance detection sensor 42 by the black mask 43. The light from the backlight 11 is reflected by the black mask 43 and enters the backlight illuminance detection sensor 42. The backlight illuminance detection sensor 42 is for detecting the illuminance of the fluorescent tube 17 that gradually decreases with time.
[0016]
Next, FIG. 5 shows the main part of the circuit of this liquid crystal display device. An external light illuminance detection unit 51 is integrally formed at a predetermined location on the upper surface of the glass substrate 3 on the back surface side of the liquid crystal display panel 1, and a backlight illuminance detection unit 52 is integrally formed at another predetermined location. ing. Both illuminance detectors 51 and 52 have the same structure. In other words, the illuminance detection units 51 and 52 include illuminance detection sensors 41 and 42 each including a double-gate photoelectric conversion thin film transistor described later, first switching elements 53 and 54 each including a thin film transistor, the illuminance detection sensors 41 and 42, and the first Resistors 55 and 56 and capacitors 57 and 58 provided between the switching elements 53 and 54, and a second switching element comprising a thin film transistor connected between the illuminance detection sensors 41 and 42 and the resistors 55 and 56. 59, 60.
[0017]
And while the sensor drive signal output from the frequency dividers 61 and 62 for a preset time is being input to the second switching elements 59 and 60, the illuminance detection sensors 41 and 42 correspond to the detected illuminance. A current flows through the capacitors 57 and 58, and charges are accumulated in the capacitors 57 and 58. When the first switching elements 53 and 54 are turned on at a predetermined timing, a light detection signal corresponding to the electric charge accumulated in the capacitors 57 and 58 is input to the level shift adjusters 63 and 64. The level shift adjusters 63 and 64 include, for example, A / D converters, convert the input photodetection signals into parallel signals, and output the parallel signals to the parallel-serial converters 65 and 66. The parallel / serial converters 65 and 66 convert the input parallel signal into a serial signal and output the serial signal to the adder 67. The adder 67 adds the input serial signals and outputs the added signal to the dimming control signal generator 68. The dimming control signal generator 68 outputs a dimming control signal corresponding to the input addition signal to the inverter 69 with a dimming function. The inverter 69 with the dimming function is configured such that the light source 16 (see FIG. 1) emits light having a luminance corresponding to the dimming control signal from the dimming control signal generator 68. Drive.
[0018]
Next, the control of the luminance of light from the light source 16 according to the ambient illuminance by the light source luminance control means will be described with specific numerical values. First, FIG. 6 shows the relationship between the screen luminance of the liquid crystal display panel 1 and the ambient illuminance in this case. As a precondition, the suitable screen brightness of the liquid crystal display panel 1 according to the environmental illuminance is 20 to 200 nits at an environmental illuminance of 50 lux such as under a streetlight at night, as in a room when the indoor lighting is turned on. The ambient illumination of 1000 lux is 30 to 300 nits, the ambient illumination of 30000 lux like the shade in a sunny day is 400 to 4000 nits, and more preferably, the ambient illumination of 50 lux is 20 to 60 nits and 1000 lux. It is assumed that the ambient illuminance is 60 to 200 knit, and the ambient illuminance is 30000 lux, 1000 to 3000 knit.
[0019]
The screen luminance L (knit) of the liquid crystal display panel 1 is the environmental illuminance I (lux), the luminance of light from the light source 16 is B (knit), and the light transmittance of the liquid crystal display panel 1 is T (%). When the reflectance of the entire apparatus is R (%), the following equation (1) is obtained.
L = I × R / 400 + B × T / 100 (1)
[0020]
Therefore, first, the screen luminance L of the liquid crystal display panel 1 is in the range of 20 to 200 nits with an environmental illuminance of 50 lux, 30 to 300 nits with an environmental illuminance of 1000 lux, and 400 to 4000 nits with an environmental illuminance of 30000 lux. The luminance of light from the light source 16 is controlled according to the ambient illuminance or the like by the light source luminance control means so that the luminance is expressed by a quadratic function that satisfies the above. That is, the control condition of the luminance of the light from the light source 16 in this case is obtained from the above equation (1) and is represented by the following equation (2).
−2 × 10 ⁻⁸ × I ² + 0.015 × I + 20 ≦ L ≦ −3 × 10 ⁻⁷ × I ² + 0.113 × I + 150 (2)
[0021]
In FIG. 6, curves M ₁ and M ₂ indicate the maximum value and the minimum value of the screen luminance L obtained from the above equation (2). That is, the curves M ₁ and M ₂ are curves represented by the following equations (3) and (4), respectively.
L (M ₁ ) = − 3 × 10 ⁻⁷ × I ² + 0.113 × I + 150 (3)
L (M ₂ ) = − 2 × 10 ⁻⁸ × I ² + 0.015 × I + 20 (4)
Therefore, a range M between the two curves M ₁ and M ₂ is a preferable range of screen luminance of the liquid crystal display panel 1 according to the environmental illuminance or the like.
[0022]
Secondly, the screen brightness L of the liquid crystal display panel 1 is 20 to 60 nits at an environmental illuminance of 50 lux, 60 to 200 nits at an environmental illuminance of 1000 lux, 1000 to 3000 nits at an environmental illuminance of 30000 lux. The light source luminance control means controls the luminance of light from the light source 16 in accordance with the ambient illuminance or the like so that the luminance is expressed by a quadratic function that satisfies each range. That is, the control condition of the luminance of the light from the light source 16 in this case is obtained from the above equation (1) and is represented by the following equation (5).
−9 × 10 ⁻⁸ × I ² + 0.0453 × I + 20 ≦ L ≦ −2 × 10 ⁻⁷ × I ² + 0.0871 × I + 50 (5)
[0023]
In FIG. 6, curves N ₁ and N ₂ indicate the maximum value and the minimum value of the screen luminance L obtained from the above equation (5). That is, the curves N ₁ and N ₂ are curves represented by the following equations (6) and (7), respectively.
L (N ₁ ) = − 2 × 10 ⁻⁷ × I ² + 0.0871 × I + 50 (6)
L (N ₂ ) = − 9 × 10 ⁻⁸ × I ² + 0.0453 × I + 20 (7)
Accordingly, the range N between the two curves N ₁ and N ₂ is a more preferable range of screen luminance of the liquid crystal display panel 1 according to the environmental illuminance or the like.
[0024]
As described above, in this liquid crystal display device, the luminance of the light from the light source 16 is controlled according to the ambient illuminance or the like by the light source luminance control means, thereby changing the screen luminance of the liquid crystal display panel 1 between the curves M ₁ and M _2. Range M, more preferably a range N between the curves N ₁ and N ₂ . Thereby, the screen luminance of the liquid crystal display panel 1 can be made suitable or more suitable in a wide environment illuminance from low illuminance to high illuminance.
[0025]
The two-dot chain line in FIG. 6 represents the screen luminance of a normal reflective liquid crystal display device that uses only external light for comparison. The screen luminance indicated by the two-dot chain line changes linearly with respect to the change in environmental illuminance. In this normal reflection type liquid crystal display device, the ambient illuminance corresponding to the range M between the curves M ₁ and M _{2 is in} the range of about 300 to about 5000 lux, and in the range N between the curves N ₁ and N _2. The corresponding ambient illuminance is in the range of about 500 to about 2000 lux. Therefore, at higher ambient illuminance, the screen of the liquid crystal display panel becomes too bright. For example, in an environment with high illuminance exceeding 100,000 lux, such as under direct sunlight in summer, the screen of the liquid crystal display panel is too dazzling. The display becomes difficult to see. On the other hand, when the ambient illuminance is lower than that, the screen of the liquid crystal display panel becomes too dark. For example, in a dark usage environment such as outdoors at night, it is impossible to obtain screen brightness enough to visually recognize the display.
[0026]
Next, a specific structure of the illuminance detection sensors 41 and 42 will be described with reference to FIG. A bottom gate electrode 71 made of a light-shielding electrode such as aluminum is provided on the upper surface of the glass substrate 3 on the back side, and a bottom gate insulating film 72 made of silicon nitride is provided on the entire upper surface. A semiconductor layer 73 made of amorphous silicon or polysilicon is provided in a portion corresponding to the bottom gate electrode 71 on the upper surface of the bottom gate insulating film 72. A blocking layer 74 made of silicon nitride is provided at the center of the upper surface of the semiconductor layer 73. N ⁺ silicon layers 75 and 76 are provided on both sides of the upper surface of the blocking layer 74 and on the upper surface of the semiconductor layer 73 on both sides thereof. A source electrode 77 and a drain electrode 78 made of a light-shielding electrode such as aluminum are provided on the upper surfaces of the n ⁺ silicon layers 75 and 76, and a top gate insulating film 79 made of silicon nitride is provided on the entire upper surface. A top gate electrode 80 made of a transparent electrode such as ITO is provided on a portion corresponding to the semiconductor layer 73 on the upper surface of the top gate insulating film 79, and an overcoat film 81 made of silicon nitride is provided on the entire upper surface. . In the illuminance detection sensors 41 and 42, light incident from the lower surface side is shielded by the bottom gate electrode 71 and is not directly incident on the semiconductor layer 73.
[0027]
In the illuminance detection sensors 41 and 42, a bottom gate type transistor is configured by the bottom gate electrode (BG) 71, the semiconductor layer 73, the source electrode (S) 77, the drain electrode (D) 78, and the like, and the top gate electrode (TG). 80, a semiconductor layer 73, a source electrode (S) 77, a drain electrode (D) 78, and the like constitute a top gate transistor. That is, the illuminance detection sensors 41 and 42 are constituted by double-gate photoelectric conversion thin film transistors in which a bottom gate electrode (BG) 71 and a top gate electrode (TG) 80 are disposed on the lower side and the upper side of the semiconductor layer 73, respectively. The equivalent circuit can be shown as in FIG.
[0028]
Next, the operation of the illuminance detection sensors 41 and 42 will be described. First, as shown in FIG. 9A, in the state where a positive voltage (for example, +5 V) is applied between the source electrode (S) and the drain electrode (D), a positive voltage (for example, +10 V) is applied to the bottom gate electrode (BG). ) Is applied, a channel is formed in the semiconductor layer 73 and a drain current flows. In this state, when a negative voltage (for example, −20 V) at a level that eliminates the channel due to the electric field of the bottom gate electrode (BG) is applied to the top gate electrode (TG), the electric field from the top gate electrode (TG) The channel is pinched off by acting in a direction to prevent the channel formation due to the electric field of the gate electrode (BG). At this time, when the semiconductor layer 73 is irradiated with light from the top gate electrode (TG) side, an electron-hole pair is induced on the top gate electrode (TG) side of the semiconductor layer 73. This electron-hole pair is accumulated in the channel region of the semiconductor layer 73 and cancels the electric field of the top gate electrode (TG). For this reason, a channel is formed in the semiconductor layer 73 and a drain current flows. This drain current changes according to the amount of light incident on the semiconductor layer 73. Then, charges are accumulated in the capacitors 57 and 58 shown in FIG. 5 by this drain current.
[0029]
Next, a case where the illuminance detection sensors 41 and 42 are reset will be described with reference to FIG. When a positive voltage (+10 V) is applied to the bottom gate electrode (BG), if the top gate electrode (TG) is set to 0 V, for example, holes from the trap level between the semiconductor layer 73 and the top gate insulating film 79 are generated. Can be refreshed, that is, reset. That is, when used continuously, the trap level between the semiconductor layer 73 and the top gate insulating film 79 is filled with holes generated by light irradiation and holes injected from the drain electrode (D). As a result, the channel resistance in the no light incident state decreases, and the drain current increases when no light is incident. Therefore, the top gate electrode (TG) is set to 0 V, and the holes are discharged and reset.
[0030]
By the way, when the reaction time until the drain current of the illuminance detection sensors 41 and 42 reaches 1 μA with respect to the illuminance of outside light was examined, the result shown in FIG. 10 was obtained as an example. As is apparent from this figure, the reaction time until the drain currents of the illuminance detection sensors 41 and 42 reach 1 μA becomes shorter as the illuminance of outside light increases. As a result, the environmental illuminance and the backlight illuminance can be obtained from the reaction time. Therefore, for example, the timing at which the first switching elements 53 and 54 shown in FIG. 5 are turned on may be the time when a current of 1 μA or more flows from the illuminance detection sensors 41 and 42. When the drain current reaches 0.1 μA, the reaction time is about 1/10, and when the drain current reaches 10 μA, the reaction time is about 10 times.
[0031]
Next, an example of a method for forming the illuminance detection sensors 41 and 42 will be described with reference to FIG. 11 together with a method for forming a MIS thin film transistor as a switching element in an active matrix liquid crystal display device. A gate electrode 91 made of aluminum or the like is formed in a thin film transistor forming region on the upper surface of the glass substrate 3 on the back side, and a bottom gate electrode 71 made of aluminum or the like is formed in an illuminance detection sensor forming region on the same upper surface. Next, a bottom gate insulating film 72 made of silicon nitride is formed on the entire top surface. Next, a semiconductor layer 92 made of amorphous silicon or polysilicon is formed in the formation region of the thin film transistor or the like on the upper surface of the bottom gate insulating film 72, and a semiconductor layer 73 made of amorphous silicon or polysilicon is formed in the illuminance detection sensor formation region on the same upper surface. Form. Next, blocking layers 93 and 74 made of silicon nitride are formed at the center of the upper surface of the semiconductor layers 92 and 73. Next, n ⁺ silicon layers 94, 95, 75, 76 are formed on both upper surfaces of the blocking layers 93, 74 and on the upper surfaces of the semiconductor layers 92, 73 on both sides thereof. Next, a source electrode 96, a drain electrode 97, a source electrode 77, and a drain electrode 78 made of aluminum or the like are formed on the upper surfaces of the n ⁺ silicon layers 94, 95, 75, and 76. Next, a top gate insulating film 79 made of silicon nitride is formed on the entire upper surface. Next, a pixel electrode 98 made of a transparent electrode such as ITO is formed in a thin film transistor forming region on the upper surface of the top gate insulating film 79, and a top gate electrode made of a transparent electrode such as ITO in the illuminance detection sensor forming region on the upper surface. 80 is formed. In this case, the pixel electrode 98 is connected to the source electrode 96 through a contact hole 99 formed in the top gate insulating film 79. Next, an overcoat film 81 made of silicon nitride is formed on the entire upper surface excluding a predetermined portion of the pixel electrode 98.
[0032]
Thus, the MIS thin film transistor and the pixel electrode 98 are formed in the thin film transistor formation region, and the illuminance detection sensor including the MIS thin film transistor is formed in the illuminance detection sensor formation region. Thus, the illuminance detection sensors 41 and 42 can be formed simultaneously with the formation of the MIS thin film transistors and the pixel electrodes 98 as switching elements, so that the number of manufacturing steps can be prevented from increasing. Moreover, since the illuminance detection sensors 41 and 42 are integrally formed on the glass substrate 3 on the back surface side of the liquid crystal display panel 1, the number of components is prevented from increasing even if the illuminance detection sensors 41 and 42 are provided. be able to.
[0033]
In addition, although the said embodiment demonstrated the case where the external light illumination intensity detection sensor 41 was formed in the upper surface of the protrusion part of the glass substrate 3 of a back surface as shown in FIG. 4, it is not limited to this. For example, as shown in FIG. 12, an external light illuminance detection sensor 41 is formed at a predetermined portion of the upper surface of the glass substrate 3 on the back surface outside the sealing material 4 shown in FIG. You may make it do. In this case, the external light is exposed to the glass substrate 2 on the front side (in the case where a color filter made of a resin containing a pigment is formed on the lower surface of the glass substrate 2, the glass substrate 2 and the color filter). In addition, since the light passes through the opening 43a formed in the black mask 43 and enters the external light illuminance detection sensor 41, the amount of external light is reduced by several tens of percent. Therefore, compared with the case shown in FIG. 4, the reaction time with respect to the external light of the external light illuminance detection sensor 41 can be made slightly longer. Therefore, when two types of external light illuminance detection sensors 41 shown in FIG. 4 and FIG. 12 are installed, the sensitivity range can be widened.
[0034]
Moreover, although the case where the double gate type photoelectric conversion thin film transistor was used as the illuminance detection sensors 41 and 42 has been described in the above embodiment, the present invention is not limited to this, and a pn type that can be formed simultaneously with the formation of the thin film transistor as the switching element. An optical diode or the like may be used. Moreover, although the case where the fluorescent tube 17 was used was demonstrated in the said embodiment, not only this but a linear light emitting diode array etc. may be used. Moreover, although the said embodiment demonstrated the case where the backlight 11 which consists of the light guide 15 etc. which have the reflecting film 24 on the step-shaped step surface 22 was used, it is not limited to this. For example, although not shown, an optical sheet may be arranged on the back side of the liquid crystal display panel, and a backlight made of EL or the like may be arranged on the back side. Furthermore, although the case where this invention was applied to the liquid crystal display device was demonstrated in the said embodiment, it can apply not only to this but to the display apparatus provided with the other non-light-emitting display panel.
[0035]
【The invention's effect】
As described above, according to the present invention, the external light illuminance detection sensor and the backlight illuminance detection sensor are integrally formed on the same surface of the display panel. There can be prevented from being increased, also, by ejecting holes Ru can refresh (reset) from the trap level between the semiconductor layer and the top gate insulating film.
[Brief description of the drawings]
FIG. 1 is a side view of a main part of a liquid crystal display device to which an embodiment of the present invention is applied.
FIGS. 2A and 2B are diagrams for explaining the progress of light in part of a liquid crystal display device. FIGS.
FIG. 3 is a perspective view for explaining an optical sheet.
FIG. 4 is a side view showing a schematic configuration of a part of a liquid crystal display device.
FIG. 5 is a circuit diagram of a main part of a liquid crystal display device.
FIG. 6 is a diagram showing a relationship between screen luminance of a liquid crystal display panel and environmental illuminance.
FIG. 7 is a cross-sectional view showing a specific structure of an illuminance detection sensor.
8 is an equivalent circuit diagram of the illuminance detection sensor shown in FIG.
9A and 9B are views for explaining the operation of the illuminance detection sensor.
FIG. 10 is a diagram showing a reaction time until the drain current of the illuminance detection sensor reaches 1 μA with respect to the illuminance of external light.
FIG. 11 is a cross-sectional view for explaining an example of a method for forming an illuminance detection sensor.
FIG. 12 is a side view showing another installation example of an external light illuminance detection sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Liquid crystal display panel 2, 3 Glass substrate 11 Backlight 41 Outside light illuminance detection sensor 42 Backlight illuminance detection sensor

Claims (1)

A display device capable of performing display using both light from a backlight disposed on the back side of a non-light emitting display panel having a pair of opposing substrates and external light simultaneously, An external light illuminance detection sensor that is integrally formed with the display panel and detects the illuminance of external light; a backlight illuminance detection sensor that is integrally formed with the display panel and detects the illuminance of light from the backlight; Backlight luminance control means for controlling the luminance of light from the backlight based on the detection result by the external light illuminance detection sensor and the detection result by the backlight illuminance detection sensor, the external light illuminance detection sensor and the backlight the light illuminance detecting sensor is integrally formed in the upper surface of the back side of the substrate of the display panel, the external light illuminance detecting sensor and the backlight Illumination detection sensor is disposed a first gate electrode made of a light-blocking material on the back side, have a second gate electrode made of a transparent material on the surface side is formed by arranged photoelectric TFT The backlight illuminance detection sensor is formed on a portion of the upper surface of the back-side substrate facing a reflective layer formed on the lower surface of the substrate on the front surface side of the display panel, and light from the backlight is transmitted to the reflective layer. in is reflected is incident on the backlight illuminance sensor display device comprising Rukoto.

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