WO2012063910A1

WO2012063910A1 - Liquid crystal display device

Info

Publication number: WO2012063910A1
Application number: PCT/JP2011/075956
Authority: WO
Inventors: 広西相地
Original assignee: シャープ株式会社
Priority date: 2010-11-11
Filing date: 2011-11-10
Publication date: 2012-05-18

Abstract

The present invention is intended to provide a liquid crystal device that can prevent a reduction of output voltage in a photodiode, while the light from the backlight is circumvented from impinging on the photodiode. This liquid crystal device comprises: an active matrix substrate (16); an opposing substrate (18) that is disposed opposite to the active matrix substrate; a liquid crystal layer (20) that is enclosed between the active matrix substrate and the opposing substrate; and a backlight that is disposed on the opposite side from the active matrix substrate side with respect to the opposing substrate. The active matrix substrate comprises: a base substrate (32); a photodiode (26) comprising a semiconductor film (34) that is formed further toward the liquid crystal layer side than the base substrate; insulating films (38,40,50) that cover the photodiode; and a light excluding film (52) that is formed on the insulating films, and that prevents the light from the backlight from impinging on the photodiode.

Description

Liquid crystal display

The present invention relates to a liquid crystal display device provided with a photodiode.

Conventionally, in order to realize a touch sensor function or the like, a liquid crystal display device provided with a photodiode is known. For example, Japanese Patent Laying-Open No. 2008-287061 (Patent Document 1) discloses a liquid crystal device in which a photodiode including a semiconductor film having an n-type semiconductor region, an intrinsic semiconductor region, and a p-type semiconductor region is formed on a substrate. Has been.

Incidentally, in a liquid crystal display device provided with a photodiode, it is necessary to prevent light from the backlight from entering the photodiode. Therefore, in the liquid crystal device described in Patent Document 1, a light shielding film is disposed between a semiconductor film included in the photodiode and the substrate.

However, if a light shielding film is disposed between the substrate and the semiconductor film, a parasitic capacitance is formed between the semiconductor film and the light shielding film. As a result, there is a problem that the output voltage of the photodiode is lowered.

An object of the present invention is to provide a liquid crystal display device having a novel structure capable of preventing a decrease in output voltage of a photodiode while preventing light from a backlight from entering the photodiode.

The liquid crystal display device of the present invention includes an active matrix substrate, a counter substrate disposed to face the active matrix substrate, a liquid crystal layer sealed between the active matrix substrate and the counter substrate, and the counter substrate In contrast, a backlight disposed on the side opposite to the active matrix substrate side is provided, the active matrix substrate being formed on the liquid crystal layer side of the base substrate and the n-type semiconductor. A photodiode including a semiconductor film having a region, an intrinsic semiconductor region, and a p-type semiconductor region; an insulating film covering the photodiode; and a light of the backlight incident on the photodiode. And a light-shielding film that prevents this.

According to the liquid crystal display device of the present invention, it is possible to prevent the output voltage of the photodiode from decreasing while avoiding the light from the backlight entering the photodiode.

1 is a schematic diagram showing a schematic configuration of a liquid crystal display device as one embodiment of the present invention. FIG. 2 is an enlarged plan view showing a main part of an active matrix substrate included in the liquid crystal display device shown in FIG. 1. FIG. 2 is a schematic diagram illustrating a schematic configuration of a photodiode included in the liquid crystal panel illustrated in FIG. 1. FIG. 2 is an equivalent circuit diagram of an optical sensor unit in the liquid crystal display device shown in FIG. 1. The schematic diagram for demonstrating the application example of the liquid crystal display device as one Embodiment of this invention. The schematic diagram for demonstrating the other application example of the liquid crystal display device as one Embodiment of this invention.

A liquid crystal display device according to an embodiment of the present invention includes an active matrix substrate, a counter substrate disposed to face the active matrix substrate, and a liquid crystal layer sealed between the active matrix substrate and the counter substrate. And a backlight disposed opposite to the active matrix substrate side with respect to the counter substrate, and the active matrix substrate is formed on the liquid crystal layer side of the base substrate and the base substrate. A photodiode including a semiconductor film having an n-type semiconductor region, an intrinsic semiconductor region, and a p-type semiconductor region, an insulating film covering the photodiode, and the light from the backlight is formed on the insulating film. A light-shielding film that prevents the light from entering the photodiode (first configuration).

In the first configuration, a light shielding film is formed. Therefore, it is possible to prevent light from the backlight from entering the photodiode.

By increasing the thickness of the insulating film, the parasitic capacitance formed between the semiconductor film and the light shielding film can be reduced. Therefore, it is possible to prevent a decrease in the output voltage of the photodiode.

According to a second configuration, in the first configuration, the active matrix substrate further includes wiring formed on the liquid crystal layer side of the photodiode and on the base substrate side of the light shielding film. And the light shielding film overlaps the wiring when the base substrate is viewed from the front. In such a configuration, it is possible to prevent light from the backlight from entering the photodiode by using the wiring. Therefore, the range in which the light from the backlight can be blocked is widened.

The third configuration is the first wiring in the second configuration in which the wiring extends in the row direction of the active matrix substrate. In such a configuration, the range in which the light from the backlight can be blocked extends in the column direction of the active matrix substrate.

According to a fourth configuration, in the third configuration, a plurality of the first wirings are formed side by side in the column direction of the active matrix substrate, and the active matrix substrate when the active matrix substrate is viewed from the front. The photodiode is located between two first wirings adjacent in the column direction. In such a configuration, the range in which the light from the backlight can be shielded further expands in the column direction of the active matrix substrate.

The fifth configuration is the second wiring in any one of the second to fourth configurations, wherein the wiring extends in the column direction of the active matrix substrate. In such a configuration, the range in which the light from the backlight can be shielded extends in the row direction of the active matrix substrate.

In addition, it is desirable to adopt the fifth configuration in combination with the third or fourth configuration. In this case, the range in which light from the backlight can be shielded extends in the row direction and the column direction of the active matrix substrate.

According to a sixth configuration, in the fifth configuration, a plurality of the second wirings are formed side by side in the row direction of the active matrix substrate, and the active matrix substrate when the active matrix substrate is viewed from the front. The photodiode is positioned between two second wirings adjacent in the row direction. In such a configuration, the range in which the light from the backlight can be shielded further expands in the row direction of the active matrix substrate.

According to a seventh configuration, in any one of the first to sixth configurations, the active matrix substrate is formed at a position different from the photodiode when the active matrix substrate is viewed from the front. A pixel electrode is further provided. In such a configuration, the photodiode and the pixel electrode do not overlap when the active matrix substrate is viewed from the front. Therefore, it is possible to avoid the formation of a pre-made capacitor between the photodiode and the pixel electrode.

According to an eighth configuration, in the seventh configuration, a plurality of the pixel electrodes are formed side by side in a specific direction, and the photodiode includes a plurality of the pixel electrodes when the active matrix substrate is viewed from the front. The n-type semiconductor region, the intrinsic semiconductor region, and the p-type semiconductor region are arranged in a direction orthogonal to the specific direction. In such a configuration, the intrinsic semiconductor region can be enlarged while bringing the n-type semiconductor region and the p-type semiconductor region closer to each other. As a result, the photodetection accuracy of the photodiode can be improved.

In the ninth configuration, in the seventh or eighth configuration, the pixel electrode is a reflective electrode, and the light shielding film is formed in the same layer as the reflective electrode. In such a configuration, it is easy to form a light shielding film.

In a tenth configuration, in any one of the first to ninth configurations, the semiconductor film is a low-temperature polysilicon film. The low-temperature polysilicon film is formed, for example, by irradiating an excimer laser on an amorphous silicon film formed by plasma CVD, sputtering, or the like. In this case, it is difficult to sufficiently increase the thickness of the low-temperature polysilicon film. Therefore, the photocurrent generated according to the amount of light received by the photodiode is reduced. However, if the configuration according to an embodiment of the present invention is employed, the parasitic capacitance formed between the semiconductor film and the light shielding film can be reduced by increasing the film thickness dimension of the insulating film. Therefore, it is possible to prevent a decrease in the output voltage of the photodiode. Therefore, even if the generated photocurrent is small, it can be detected.

The eleventh configuration further includes a color filter in any one of the first to tenth configurations. In such a configuration, a color image can be displayed.

In a twelfth configuration, in the eleventh configuration, the color filter is located on the opposite side of the light shielding film with respect to the photodiode. In such a configuration, a liquid crystal display device can be used as a color scanner or an IR (infrared) touch panel.

In a thirteenth configuration according to the twelfth configuration, the active matrix further includes the color filter, the color filter is closer to the liquid crystal layer than the base substrate, and more than the photodiode. It is formed on the base substrate side. In such a configuration, the color filter can be handled integrally with the active matrix substrate.

A fourteenth configuration further includes a color filter substrate having the color filter in the twelfth configuration, and the color filter substrate is attached to a surface of the active matrix substrate opposite to the liquid crystal layer side. ing. In such a configuration, the color filter and the active matrix substrate can be handled separately.

Hereinafter, more specific embodiments of the present invention will be described with reference to the drawings. In addition, each figure referred below demonstrates the simplified main component required in order to demonstrate this invention among the structural members of embodiment of this invention for convenience of explanation. Therefore, the liquid crystal display device according to the present invention can include arbitrary constituent members not shown in the drawings referred to in this specification. Moreover, the dimension of the member in each figure does not represent the dimension of an actual structural member, the dimension ratio of each member, etc. faithfully.

[Embodiment]
FIG. 1 shows a liquid crystal display device 10 as an embodiment of the present invention. The liquid crystal display device 10 includes a liquid crystal panel 12 and a backlight 14.

The liquid crystal panel 12 includes an active matrix substrate 16, a counter substrate 18, and a liquid crystal layer 20 sealed between these

substrates

16 and 18.

A plurality of pixels 22 (see FIG. 2) are formed on the active matrix substrate 16. As shown in FIG. 2, each pixel 22 includes a plurality of sub-pixels 22r, 22g, and 22b. In the present embodiment, each pixel 22 includes a red pixel 22r, a green pixel 22g, and a blue pixel 22b.

Each of the sub-pixels 22r, 22g, and 22b includes a thin film transistor (not shown) as an active element and a pixel electrode 24.

The gate electrode of the thin film transistor is connected to a gate line (not shown) extending from a gate driver (not shown). A source electrode of the thin film transistor is connected to a source line SL extending from a source driver (not shown). The drain electrode of the thin film transistor is connected to the pixel electrode 24. The pixel electrode 24, the counter electrode 58 described later, and the liquid crystal layer 20 form a charge storage capacitor that stores a given charge.

A plurality of photodiodes 26 are formed on the active matrix substrate 16. One row formed by arranging several photodiodes 26 in the row direction of the active matrix substrate 16 and one row formed by arranging several pixels 22 in the row direction of the active matrix substrate 16 Are alternately arranged in the column direction of the active matrix substrate 16. As is clear from this, in the present embodiment, the pixel electrode 24 included in each of the sub-pixels 22r, 22g, and 22b and the photodiode 26 are formed at positions that do not overlap in a plan view of the substrate 32 described later. .

In the active matrix substrate 16, one photodiode 26 is provided for four pixels 22 (12 sub-pixels 22r, 22g, and 22b). The ratio between the photodiode 26 and the pixel 22 is an arbitrary design item set in consideration of the sensitivity of the photodiode 26 and the like.

Although not shown in FIG. 2, in the formation region of the photodiode 26, a storage capacitor Cint (see FIG. 4) used for reading out the output voltage of the photodiode 26 and a read thin film transistor 30 (see FIG. 4). Are formed. The photosensor portion of the liquid crystal display device 10 is realized by including the photodiode 26, the storage capacitor Cint, and the readout thin film transistor 30.

The photodiode 26 is formed on a substrate 32 as a base substrate included in the active matrix substrate 16 as shown in FIG. As the substrate 32, for example, a low alkali glass substrate or a quartz substrate can be adopted.

The photodiode 26 includes a semiconductor film 34 provided on the substrate 32. The semiconductor film 34 is formed by the same process as a semiconductor film included in a thin film transistor (not shown).

In the present embodiment, the semiconductor film 34 is formed on the substrate 32 through the base layer 36 formed on the substrate 32. The underlayer 36 is provided to prevent impurity diffusion from the glass substrate. As the base layer 36, for example, a silicon oxide film, a silicon nitride film, or the like can be employed. The thickness of the underlayer 36 is 100 to 600 nm.

As the semiconductor film 34, for example, an amorphous silicon film or a crystalline silicon film can be employed. As the crystalline silicon film, for example, a low-temperature polysilicon film, a high-temperature polysilicon film, a continuous grain boundary silicon film, a microcrystalline silicon film, or the like can be employed. Incidentally, in this embodiment, a low-temperature polysilicon film is adopted as the semiconductor film 34. The thickness of the semiconductor film 34 is 25 to 100 nm.

In the semiconductor film 34, a p-type semiconductor region 34p, an intrinsic semiconductor region 34i, and an n-type semiconductor region 34n are formed so as to be arranged along the base layer 36 in this order. As is apparent from this, the photodiode 26 is a so-called lateral structure PIN diode.

Particularly in this embodiment, the direction in which the p-type semiconductor region 34p, the intrinsic semiconductor region 34i, and the n-type semiconductor region 34n are arranged is the column direction of the active matrix substrate 16. In the front view of the substrate 32, the photodiode 26 is located next to the pixel electrode 24 included in each of the sub-pixels 22r, 22g, and 22b. Therefore, the intrinsic semiconductor region 34i can be enlarged while bringing the p-type semiconductor region 34p and the n-type semiconductor region 34n close to each other. As a result, the light detection accuracy of the photodiode 26 can be improved. Note that the direction in which the p-type semiconductor region 34p, the intrinsic semiconductor region 34i, and the n-type semiconductor region 34n are arranged may be the row direction of the active matrix substrate 16.

A gate insulating film 38 is formed on the base layer 36 so as to cover the photodiode 26 (semiconductor film 34). As the gate insulating film 38, for example, a silicon oxide film or the like can be employed. The thickness of the gate insulating film 38 is 50 to 120 nm. The gate insulating film 38 also covers a semiconductor film (a semiconductor film having a source region, a channel region, and a drain region) included in a thin film transistor (not shown).

An interlayer insulating film 40 is formed on the gate insulating film 38 so as to cover the gate insulating film 38. As the interlayer insulating film 40, for example, a film in which a silicon nitride film and a silicon oxide film are stacked in this order can be employed. The thickness of the interlayer insulating film 40 is 500 to 1000 nm. The interlayer insulating film 40 also covers a gate electrode provided in a thin film transistor (not shown).

Note that a gate protective film for protecting a gate electrode included in a thin film transistor (not shown) may be provided below the interlayer insulating film 40. As the gate protective film, for example, a silicon oxide film or the like can be employed. The thickness of the gate protective film is 20 to 100 nm.

In the interlayer insulating film 40 and the gate insulating film 38, contact holes 42 and 44 penetrating the interlayer insulating film 40 and the gate insulating film 38 in the thickness direction are formed. The contact hole 42 is formed at a position overlapping the p-type semiconductor region 34p in the plan view of the substrate 32. The contact hole 44 is formed at a position overlapping the n-type semiconductor region 34n in plan view of the substrate 32. By forming the contact holes 42 and 44 in this way, electrodes /

wirings

46 and 48 formed on the interlayer insulating film 40 for the p-type semiconductor region 34p and the n-type semiconductor region 34n, respectively. Is connected. As the electrodes /

wirings

46 and 48, for example, those having a two-layer structure of a titanium nitride film and an aluminum film can be employed.

A planarizing film 50 is formed on the interlayer insulating film 40 so as to cover the electrodes /

wirings

46 and 48. As the planarizing film 50, for example, a silicon oxide film or the like can be employed in addition to an organic insulating film such as a photosensitive acrylic resin. The thickness of the planarizing film 50 is 1000 to 4000 nm.

A light shielding film 52 is formed on the planarizing film 50. As the light shielding film 52, for example, a metal film can be employed. Considering the manufacturing method of the active matrix substrate 16, it is desirable to employ a metal film formed of refractory metal such as tantalum, tungsten, molybdenum or the like as the light shielding film 52. The thickness of the light shielding film 52 is 50 to 200 nm. The light shielding film 52 is given a constant potential VLS (see FIG. 4) in order to prevent changes in device characteristics due to potential fluctuations.

When the liquid crystal display device 10 is a transflective type or a reflective type, the light shielding film 52 also functions as a reflective film. When the liquid crystal display device 10 is a transflective type or a reflective type, the light shielding film 52 can be formed on the same layer as the pixel electrode 24 as a reflective electrode. Thereby, it becomes possible to suppress the increase in the number of manufacturing processes. Even if the liquid crystal display device 10 is a transmissive type, the light shielding film 52 can be formed.

The light shielding film 52 is formed so as to cover the photodiode 26 in a plan view of the substrate 32 as indicated by a one-dot chain line in FIG. Thereby, the light of the backlight 14 is prevented from entering the photodiode 26 from the counter substrate 18 side.

The width dimension (dimension in the column direction of the active matrix substrate 16) of the light shielding film 52 is preferably larger than the separation distance between the two wirings RST and RWS extending in the row direction of the active matrix substrate 16. If the wirings RST and RWS are formed below the light shielding film 52 (on the side of the substrate 32), one end portion in the width direction of the light shielding film 52 overlaps with the one wiring RST in the plan view of the substrate 32. The other edge in the width direction of the film 52 overlaps the other wiring RWS. Furthermore, if the wirings RST and RWS are formed above the semiconductor film 34 (on the liquid crystal layer 20 side), the light from the backlight 14 can be blocked using the wirings RST and RWS. In the column direction of the active matrix substrate 16, it is not necessary to make the light shielding film 52 larger than necessary.

Of the two wirings RST and RWS, one wiring RST is a wiring for supplying a reset signal, and is connected to the p-type semiconductor region 34p of the photodiode 26 (see FIG. 4). The other wiring RWS is a wiring for supplying a readout signal, and is connected to one electrode of the storage capacitor Cint included in the optical sensor unit of the liquid crystal display device 10 (see FIG. 4).

The length dimension of the light shielding film 52 (dimension in the row direction of the active matrix substrate 16) may be substantially the same as the length dimension of the photodiode 26 (dimension in the row direction of the active matrix substrate 16). However, it is preferable that the distance is larger than the distance between two source lines SL and SL adjacent in the row direction of the active matrix substrate 16. If the source lines SL and SL are formed below the light shielding film 52 (on the substrate 32 side), the length of the light shielding film 52 is adjacent to the two source lines SL and SL in the row direction of the active matrix substrate 16. Is longer than the separation distance, the one edge in the length direction of the light shielding film 52 overlaps with one source line SL, and the other edge in the length direction of the light shielding film 52 overlaps with the other source line SL. . Furthermore, if the source lines SL and SL are formed in an upper layer (the liquid crystal layer 20 side) than the semiconductor film 34, the light from the backlight 14 can be shielded using the source line SL. In this way, when the light from the backlight 14 is shielded, one photodiode 26 can be shielded by using the plurality of light shielding films 52.

The counter substrate 18 is disposed so as to face the display area of the active matrix substrate 16 (the area where the plurality of pixels 22 are formed). The counter substrate 18 is disposed on the side of the active matrix substrate 16 where the plurality of pixels 22 are formed.

The counter substrate 18 includes a substrate 54 as shown in FIG. As the substrate 54, for example, a low alkali glass substrate or a quartz substrate can be adopted.

A color filter 56 and a counter electrode 58 are laminated on the substrate 54 in this order.

Although not shown, the color filter 56 includes a blue colored layer, a green colored layer, and a red colored layer. A black matrix (not shown) is formed between adjacent colored layers.

The counter electrode 58 is formed so as to cover the color filter. As the counter electrode 58, for example, an ITO (indium tin oxide) film or the like can be employed.

A liquid crystal layer 20 is sealed between the active matrix substrate 16 and the counter substrate 18. As an operation mode of the liquid crystal, for example, a TN (twisted nematic) mode or the like can be adopted.

The backlight 14 is arranged so as to illuminate such a liquid crystal panel 12 from the counter substrate 18 side. As the backlight 14, for example, a direct type, an edge light type, a planar light source type, or the like can be adopted. As a light source of the backlight 14, a cold cathode tube, a light emitting diode (LED), etc. are employable, for example.

FIG. 4 shows an equivalent circuit diagram of the optical sensor unit of such a liquid crystal display device 10. The optical sensor unit includes a photodiode 26, a storage capacitor Cint, and a readout thin film transistor 30. The wiring RST is connected to the p-type semiconductor region 34p of the photodiode 26 as described above. The other electrode of the storage capacitor Cint and the gate electrode of the readout thin film transistor 30 are connected to the n-type semiconductor region 34n of the photodiode 26. As described above, the wiring RWS is connected to one electrode of the storage capacitor Cint. A constant voltage source VDD for supplying a constant voltage is connected to the source region of the read thin film transistor 30. A wiring VOUT for taking out the output voltage (sensor signal) of the photodiode 26 is connected to the drain region of the reading thin film transistor 30. In FIG. 4, VA is a potential on the anode side of the photodiode 26 (on the p-type semiconductor region 34p side of the photodiode 26), and VC is a cathode side of the photodiode 26 (n-type of the photodiode 26). The VLS is the potential of the light shielding film 52.

In such an optical sensor unit, a sensor signal (output voltage of the photodiode 26) corresponding to the amount of light received by the photodiode 26 can be obtained by supplying a reset signal and a readout signal at a predetermined timing.

Specifically, first, when a high-level reset signal is supplied to the wiring RST, the reset period starts. Note that a low-level read signal is supplied to the wiring RWS during the reset period.

During the reset period, a forward current flows through the photodiode 26. As a result, the potential of the storage node 60 is reset. The storage node 60 is a connection point between the storage capacitor Cint, the n-type semiconductor region 34n of the photodiode 26, and the gate electrode of the read thin film transistor 30.

When the low level reset signal is supplied to the wiring RST, the reset period ends. When the reset period ends, the sensing period starts. Note that in the sensing period, a low-level read signal is supplied to the wiring RWS.

During the sensing period, a reverse bias is generated in the photodiode 26. Then, the potential of the storage node 60 is changed by the photocurrent generated according to the amount of light incident on the photodiode 26.

When a high level read signal is supplied to the wiring RWS, a read period is started. Note that in the reading period, a low-level reset signal is supplied to the wiring RST.

In the readout period, the potential of the storage node 60 is pulled up via the storage capacitor Cint. When the pulled-up potential of the storage node 60 exceeds the threshold voltage of the readout thin film transistor 30, the readout thin film transistor 30 is turned on and a sensor signal (output voltage of the photodiode 26) is output.

By repeating such an operation, a sensor signal (output voltage of the photodiode 26) can be obtained.

Incidentally, a parasitic capacitance Cls is formed between the semiconductor film 34 and the light shielding film 52. Thereby, in the sensing period, the parasitic capacitance Cls and the storage capacitance Cint are discharged for a certain period. That is, as apparent from the relationship shown in the following equation, if the photocurrent (≈Q) generated according to the amount of light incident on the photodiode 26 is substantially constant, the smaller the parasitic capacitance Cls and the storage capacitance Cint, The amount of change in the potential VC (potential of the storage node 60) on the cathode side (n-type semiconductor region 34n side) of the photodiode 26 increases.
(Equation 1)
Q = (Cls + Cint) × ΔVC
In the above equation, ΔVC represents the amount of change in the cathode side potential VC of the photodiode 26.

Therefore, in order to turn on the reading thin film transistor 30, it is necessary to apply a predetermined voltage to the gate electrode of the reading thin film transistor 30. Specifically, it is necessary to keep the value of the following formula at a certain value.
(Equation 2)
ΔVRW × Cint / (Cint + Cls)
Note that in the above equation, ΔVRW is a potential difference between the high level and the low level in the read signal (the pulse height of the read signal).

Therefore, the storage capacitor Cint cannot be arbitrarily changed, and in order to increase the output voltage (sensor signal) of the photodiode 26, it is necessary to reduce the parasitic capacitance Cls.

Therefore, in the liquid crystal display device 10, a light shielding film 52 that shields light from the backlight 14 is formed on the planarizing film 50, and the photodiode 26 (semiconductor film 34) formed on the base layer 36. Between the gate insulating film 38, the gate insulating film 38, the interlayer insulating film 40, and the planarizing film 50 exist. Thereby, the separation distance between the semiconductor film 34 and the light shielding film 52 can be increased as compared with the case where the light shielding film is formed on the substrate 32. That is, in the case where the light shielding film is formed on the substrate 32, if the thickness of the foundation layer 36 existing between the light shielding film and the photodiode 26 (semiconductor film 34) is increased, the stress of the foundation layer 36 Since the substrate 32 is warped and the subsequent manufacturing process cannot be performed, the thickness of the base layer 36 (insulating film) is increased, and the light shielding film and the photodiode 26 (semiconductor film 34) are formed. However, in this embodiment, the insulating film (gate insulating film 38, interlayer insulating film) existing between the light shielding film 52 and the photodiode 26 (semiconductor film 34) is not able to be increased. 40 and the planarizing film 50) can be prevented from causing the above-described problems caused by the stress of the film, so that the insulating films (gate insulating film 38, interlayer insulating film 4) can be avoided. And by increasing the thickness of the flattening film 50), it is possible to increase the distance between the light shielding film 52 and the photodiode 26 (semiconductor film 34). As a result, the parasitic capacitance Cls formed between the semiconductor film 34 and the light shielding film 52 can be reduced. As is clear from this, in the present embodiment, an insulating film is realized by the gate insulating film 38, the interlayer insulating film 40 and the planarizing film 50.

Incidentally, Table 1 shows the parasitic capacitance (parasitic capacitance formed between the photodiode and the light shielding film) of the present embodiment and the conventional configuration. The conventional configuration is a configuration in which the light shielding film 52 is formed on the substrate 32. In other words, in the conventional configuration, only the base layer 36 exists between the photodiode 26 (semiconductor film 34) and the light shielding film 52. In the conventional configuration, the base layer 36 is formed by laminating a silicon nitride film and a silicon oxide film. In addition to the parasitic capacitance, Table 1 also shows the type of film existing between the photodiode 26 (semiconductor film 34) and the light shielding film 52, the relative dielectric constant of each film, and the film thickness of each film. ing.

As is clear from Table 1, in this embodiment, the parasitic capacitance can be reduced to about 1/10 as compared with the conventional configuration.

Therefore, in the liquid crystal display device 10, the output voltage (sensor signal) of the photodiode 26 can be increased. As a result, the sensitivity of the photodiode 26 can be improved.

Particularly in the present embodiment, the pixel electrode 24 is formed at a position where it does not overlap the photodiode 26 in the plan view of the substrate 32. Thereby, it is possible to avoid the formation of parasitic capacitance between the pixel electrode 24 and the photodiode 26 (semiconductor film 34).

In the present embodiment, the gate insulating film 38, the interlayer insulating film 40, and the planarizing film 50 exist between the photodiode 26 (semiconductor film 34) and the light shielding film 52, and the substrate 32. The pixel electrode 24 is formed at a position where it does not overlap the photodiode 26 in plan view. Thereby, the adverse effect of the pixel electrode 24 and the light shielding film 52 on the photodiode 26 can be reduced. That is, in a configuration in which an insulating film exists between the photodiode 26 (semiconductor film 34) and an electrode (pixel electrode or light shielding film), the characteristics of the photodiode change when the thickness or quality of the insulating film changes. Although there is a problem of changing (so-called electrode gate action), this embodiment can avoid such a problem.

In the present embodiment, the semiconductor film 34 is a polysilicon film. When a method of irradiating an excimer laser to an amorphous silicon film formed on the underlayer 36 by plasma CVD, sputtering, or the like is employed as a method for forming a polysilicon film, the thickness of the polysilicon film is sufficiently increased. Therefore, although the photocurrent generated according to the amount of light received by the photodiode 26 is originally small, in this embodiment, the output voltage of the photodiode 26 can be increased, so even if the generated photocurrent is small. Can be detected.

In the present embodiment, the sensitivity of the photodiode 26 is improved. As a result, the number of photodiodes 26 to be employed can be reduced and the transmittance of the liquid crystal panel 12 can be improved.

In the present embodiment, the sensitivity of the photodiode 26 is improved. As a result, the number of photodiodes 26 to be employed can be increased and the resolution can be improved.

[Application example of embodiment]
In the embodiment, the color filter 56 may be provided on the active matrix substrate 16 side. Accordingly, the liquid crystal display device can be used as a color scanner or an IR (infrared) touch panel.

When the color filter 56 is provided on the active matrix substrate 16 side, for example, the color filter 56 may be formed on the substrate 32 as shown in FIG. In FIG. 5, the color filter 56 is covered with an overcoat film 62, and the base layer 36 is formed so as to cover the overcoat film 62. As the overcoat film 62, a silicon oxide film, a silicon nitride film, or the like can be employed. The film thickness of the overcoat film 62 is 1000 to 3000 nm. Note that the overcoat film 62 and the base layer 36 may be formed of the same film.

Alternatively, as shown in FIG. 6, a color filter substrate 64 on which the color filter 56 is formed may be prepared separately, and the color filter substrate 64 may be attached to the active matrix substrate 16 from the outside. In the color filter substrate 64, the color filter 56 formed on the substrate 66 is covered with the overcoat film 62. As the substrate 66, for example, a glass substrate or an acrylic substrate can be employed.

As mentioned above, although embodiment of this invention has been explained in full detail, these are illustrations to the last and this invention is not limited at all by the above-mentioned embodiment.

For example, in the above-described embodiment, each pixel 22 may include a yellow pixel in addition to the red pixel 22r, the green pixel 22g, and the blue pixel 22b.

Claims

An active matrix substrate;
A counter substrate disposed opposite to the active matrix substrate;
A liquid crystal layer sealed between the active matrix substrate and the counter substrate;
A backlight disposed on the opposite side of the counter substrate with respect to the active matrix substrate side,
The active matrix substrate is
A base substrate;
A photodiode including a semiconductor film formed on the liquid crystal layer side of the base substrate and having an n-type semiconductor region, an intrinsic semiconductor region, and a p-type semiconductor region;
An insulating film covering the photodiode;
A liquid crystal display device comprising: a light shielding film that is formed on the insulating film and prevents light from the backlight from entering the photodiode.
The active matrix substrate is
It further includes wiring formed on the liquid crystal layer side of the photodiode and on the base substrate side of the light shielding film,
The liquid crystal display device according to claim 1, wherein the light-shielding film overlaps the wiring when the base substrate is viewed from the front.
3. The liquid crystal display device according to claim 2, wherein the wiring is a first wiring extending in a row direction of the active matrix substrate.
A plurality of the first wirings are formed side by side in the column direction of the active matrix substrate;
4. The liquid crystal display device according to claim 3, wherein, when the active matrix substrate is viewed from the front, the photodiode is positioned between two first wirings adjacent in the column direction of the active matrix substrate. 5.
The liquid crystal display device according to any one of claims 2 to 4, wherein the wiring is a second wiring extending in a column direction of the active matrix substrate.
A plurality of the second wirings are formed side by side in the row direction of the active matrix substrate;
The liquid crystal display device according to claim 5, wherein the photodiode is positioned between two second wirings adjacent in the row direction of the active matrix substrate when the active matrix substrate is viewed from the front.
The active matrix substrate is
7. The liquid crystal display device according to claim 1, further comprising a pixel electrode formed at a position different from the photodiode when the active matrix substrate is viewed from the front.
A plurality of the pixel electrodes are formed side by side in a specific direction,
When the active matrix substrate is viewed from the front, the photodiode is located next to the plurality of pixel electrodes,
The liquid crystal display device according to claim 7, wherein the n-type semiconductor region, the intrinsic semiconductor region, and the p-type semiconductor region are arranged in a direction orthogonal to the specific direction.
The pixel electrode is a reflective electrode;
The liquid crystal display device according to claim 7, wherein the light shielding film is formed in the same layer as the reflective electrode.
The liquid crystal display device according to any one of claims 1 to 9, wherein the semiconductor film is a low-temperature polysilicon film.
The liquid crystal display device according to any one of claims 1 to 10, further comprising a color filter.
The liquid crystal display device according to claim 11, wherein the color filter is located on a side opposite to the light shielding film with respect to the photodiode.
The active matrix further comprises the color filter;
The liquid crystal display device according to claim 12, wherein the color filter is formed closer to the liquid crystal layer than the base substrate and closer to the base substrate than the photodiode.
A color filter substrate having the color filter;
The liquid crystal display device according to claim 12, wherein the color filter substrate is attached to a surface of the active matrix substrate opposite to the liquid crystal layer side.