JP2011242760A - Liquid crystal display device and driving method of liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device that has a display function and an imaging function and can perform bright display and high-accuracy imaging.SOLUTION: A liquid crystal display device has a display function and an imaging function, and performs white display (bright display) by utilizing scattering light of liquid crystal, using a polymer dispersion type liquid crystal material in a liquid crystal layer. The liquid crystal display device further comprises the liquid crystal layer and a light-receiving element. The liquid crystal layer is disposed on a viewing side with respect to the light-receiving element, and the light-receiving element has light-receiving sensitivity to an infrared wavelength region. The light-receiving element having light-receiving sensitivity to the infrared wavelength region detects infrared light in the incident light. The liquid crystal display device performs imaging with infrared light detected by the light-receiving element.

Description

  The present invention relates to a liquid crystal display device and a driving method of the liquid crystal display device. In particular, the present invention relates to a liquid crystal display device having a display function and an imaging function, and a driving method of the liquid crystal display device.

  In recent years, in response to the trend of the electronic book business, development of electronic book terminals such as electronic paper has been active. Further, it is expected to be usable not only as an electronic book terminal but also as a portable information terminal such as a mobile phone.

  However, at present, it is difficult to make the color, brightness, reflectance, and the like of the display screen exactly the same as the paper surface in a terminal for electronic books. For this reason, it is said that viewers are likely to feel eye fatigue when they read electronic books as if they were newspapers or paperbacks printed on paper.

  In addition, a touch panel is known that has an input function by providing a display device with an imaging function. For example, Patent Document 1 discloses a portable information terminal in which a touch panel is combined with electronic paper.

  A new application can be developed by providing a touch panel function to a display unit such as a portable information terminal. Furthermore, if such a portable information terminal can be used as an electronic book terminal, it is possible to have a telephone function, an electronic book function, a display function for a television or a digital photo frame, etc. in one terminal. Become.

JP 2009-098795 A

  According to one embodiment of the present invention, it is an object to provide a liquid crystal display device including a display function and an imaging function and capable of bright display. Another object of one embodiment of the present invention is to provide a liquid crystal display device including a display function and an imaging function and capable of display close to paper.

  Another object of one embodiment of the present invention is to provide a liquid crystal display device that includes a display function and an imaging function and can perform high-accuracy imaging.

  Another object of one embodiment of the present invention is to provide a liquid crystal display device that includes a display function and an imaging function, and can perform high-accuracy imaging with a bright display. Another object of one embodiment of the present invention is to provide a liquid crystal display device that has a display function and an imaging function and can display images close to a paper surface and perform high-accuracy imaging.

  The disclosed invention is a liquid crystal display device having a display function and an imaging function. A polymer dispersed liquid crystal (PDLC: Polymer Dispersed Liquid Crystal) material is used for a liquid crystal layer included in the liquid crystal display device. By using a polymer dispersed liquid crystal material, white display (bright display) is performed using scattered light from the liquid crystal material. The liquid crystal layer has a configuration in which a liquid crystal material is dispersed in a polymer material that forms a polymer network.

  The polymer dispersed liquid crystal is also referred to as polymer dispersed liquid crystal or polymer dispersed liquid crystal. Further, a polymer network type liquid crystal (PNLC: Polymer Network Liquid Crystal) can be used instead of the polymer dispersion type liquid crystal. Even when a polymer network type liquid crystal is used, white display (bright display) can be performed using scattered light of light from the liquid crystal material.

  In addition, a liquid crystal display device of the disclosed invention includes a liquid crystal layer and a light receiving element, the liquid crystal layer is disposed on the viewing side of the light receiving element, and the light receiving element has light receiving sensitivity in an infrared wavelength region. A light receiving element having light receiving sensitivity in the infrared wavelength region detects infrared light from incident light. The liquid crystal display device has a function of imaging using infrared rays detected by a light receiving element.

  One embodiment of the present invention has a display function and an imaging function, includes a liquid crystal layer and a light receiving element. The liquid crystal layer is disposed on the viewing side of the light receiving element, includes a polymer-dispersed liquid crystal material, The element is a liquid crystal display device having light receiving sensitivity in an infrared wavelength region and having a function of imaging infrared light detected by the light receiving element.

  One embodiment of the present invention includes a display function and an imaging function, and includes a counter electrode, a pixel electrode, a liquid crystal layer, and a light receiving element, and the counter electrode, the pixel electrode, and the liquid crystal layer are on the viewing side of the light receiving element. The counter electrode is disposed closer to the viewing side than the pixel electrode and the liquid crystal layer, transmits visible light, the pixel electrode is disposed facing the counter electrode, reflects visible light, and the liquid crystal layer is A liquid crystal display device, which is sandwiched between a counter electrode and a pixel electrode, includes a polymer-dispersed liquid crystal material, and has a function of imaging infrared rays detected by a light receiving element. It is preferable that no pixel electrode is disposed at a position overlapping the light receiving element.

  One embodiment of the present invention has a display function and an imaging function, and includes a counter electrode, a pixel electrode, a liquid crystal layer, a black layer, and a light receiving element, and the counter electrode, the pixel electrode, and the liquid crystal layer Is disposed on the viewing side of the black layer and the light receiving element, the counter electrode is disposed on the viewing side of the pixel electrode and the liquid crystal layer, and transmits visible light, and the pixel electrode The liquid crystal layer is disposed between the counter electrode and the pixel electrode, includes a polymer-dispersed liquid crystal material, and the light receiving element is an infrared ray. A liquid crystal display device having a light receiving sensitivity in a wavelength region and having a function of imaging an infrared ray detected by the light receiving element. It can be set as the structure by which the black layer is arrange | positioned in the position which overlaps with a light receiving element.

  Further, in the above structure, a liquid crystal display device having an infrared transmission filter disposed on a position opposite to the viewing side with respect to the liquid crystal layer and overlapping the light receiving element can be obtained.

  Note that in this specification, a potential at a high level is also simply referred to as “H” or “high”. The potential at the low level is also simply referred to as “L” or “low”.

  Further, in this specification and the like, the terms “electrode” and “wiring” do not functionally limit these components. For example, an “electrode” may be used as part of a “wiring” and vice versa. Furthermore, the terms “electrode” and “wiring” include a case where a plurality of “electrodes” or a plurality of “wirings” are integrally formed.

  In addition, the functions of “source” and “drain” may be switched when transistors having different polarities are employed, or when the direction of current changes during circuit operation. Therefore, in this specification, the terms “source” and “drain” can be used interchangeably.

  Note that in this specification and the like, “electrically connected” includes a case of being connected via “something having an electric action”. Here, the “thing having some electric action” is not particularly limited as long as it can exchange electric signals with respect to the connection target. For example, “thing having some electric action” includes electrodes, wiring, switching elements such as transistors, resistance elements, inductors, capacitors, and other elements having various functions.

  According to one embodiment of the present invention, a liquid crystal display device that can perform bright display and has a display function and an imaging function can be provided. Alternatively, according to one embodiment of the present invention, a liquid crystal display device including a display function and an imaging function that can be displayed close to a paper surface can be provided. Alternatively, according to one embodiment of the present invention, a liquid crystal display device including a display function and an imaging function that can capture images with high accuracy can be provided.

FIGS. 4A and 4B are schematic views of a top surface and a cross section illustrating a liquid crystal display device. FIG. 9 is a schematic cross-sectional view illustrating a liquid crystal display device. 6A and 6B illustrate a structure of a liquid crystal display device. FIG. 6 illustrates a circuit configuration of a pixel of a liquid crystal display device. 3A and 3B each illustrate a circuit configuration of a liquid crystal display device. The figure explaining a timing chart. 3A and 3B each illustrate a circuit configuration of a liquid crystal display device. 3A and 3B each illustrate a circuit configuration of a liquid crystal display device. 3A and 3B each illustrate a circuit configuration of a liquid crystal display device. FIG. 10 illustrates an electronic device. FIG. 10 illustrates an electronic device. The figure which shows the wavelength dispersion characteristic of the transmittance | permeability.

  Hereinafter, embodiments will be described in detail with reference to the drawings. However, the following embodiments can be implemented in many different modes, and it is easy for those skilled in the art to change the modes and details in various ways without departing from the spirit and scope thereof. Understood. Therefore, the present invention is not construed as being limited to the description of the embodiments below. Note that in all the drawings for describing the embodiments, the same portions or portions having similar functions may be denoted by the same reference numerals, and repetitive description will be omitted.

(Embodiment 1)
FIG. 1 shows an example of a liquid crystal display device having a display function and an imaging function.

  FIG. 1A is a schematic view of the top surface of a pixel included in the liquid crystal display device according to this embodiment. The pixel 1000 includes a display element 1100 and a photosensor 1200.

  FIG. 1B is a schematic diagram of a cross section between broken lines PQ in FIG. A part of the display element 1100 is shown on the right side of the page from the two-dot chain line in FIG. 1B, and a part of the photosensor 1200 is shown on the left side of the page.

  In FIG. 1B, a pixel 1000 of the liquid crystal display device includes a liquid crystal layer 1303 and a light receiving element 1201, and the liquid crystal layer 1303 is arranged on the viewing side with respect to the light receiving element 1201.

  The liquid crystal display device in this embodiment is a reflective liquid crystal display device. In the liquid crystal display device illustrated in FIG. 1B, a liquid crystal layer 1303 is provided between a first substrate 1003 over which an element such as a light receiving element 1201 is provided and a second substrate 1013 which is a counter substrate. It is visually recognized from the second substrate 1013 side. In addition, the object to be detected positioned on the second substrate 1013 side is imaged.

  The liquid crystal layer 1303 is sandwiched between a counter electrode 1305 arranged on the viewing side and a pixel electrode 1301 arranged facing the counter electrode 1305.

  The liquid crystal layer 1303 includes a polymer dispersed liquid crystal material or a polymer network type liquid crystal material, and the liquid crystal material is dispersed in a polymer material that forms a polymer network.

  In the liquid crystal layer 1303, when no voltage is applied between the pixel electrode 1301 and the counter electrode 1305 (also referred to as an off state), liquid crystal molecules dispersed in the polymer material are randomly arranged. At this time, since the refractive index of the polymer material and the refractive index of the liquid crystal molecules are different, light incident on the liquid crystal layer 1303 is scattered by the liquid crystal molecules. As a result, the liquid crystal layer 1303 does not have translucency and appears cloudy. Therefore, the display that can be confirmed from the viewing side (the second substrate 1013 side) is white display (bright display).

  Further, in the liquid crystal layer 1303, when a voltage is applied between the pixel electrode 1301 and the counter electrode 1305 (also referred to as an on state), an electric field is formed in the liquid crystal layer 1303, and the liquid crystal molecules are aligned in the direction of the electric field. At this time, since the refractive index of the polymer material and the refractive index of the short axis of the liquid crystal molecules are substantially the same, the light incident on the liquid crystal layer 1303 is not scattered by the liquid crystal molecules but is transmitted through the liquid crystal layer 1303. Accordingly, the liquid crystal layer 1303 has a light-transmitting state. At that time, the display that can be confirmed from the viewing side depends on the materials provided before and after (up and down) the liquid crystal layer 1303. At that time, by making the pixel electrode 1301 disposed on the opposite side of the liquid crystal layer 1303 to the viewing side an electrode that reflects visible light, a display that can be confirmed from the viewing side can be a black display (dark display). Alternatively, by disposing the black layer on the side opposite to the viewing side of the liquid crystal layer 1303, the display that can be confirmed from the viewing side can be made black.

  Note that the thickness of the liquid crystal layer 1303 is preferably 5 to 30 μm. By setting it as such a range, power consumption can be suppressed.

  The counter electrode 1305 is an electrode that transmits visible light, and is disposed on the opposite side of the liquid crystal layer 1303 from the viewing side.

  The pixel electrode 1301 is disposed on the side opposite to the viewing side of the liquid crystal layer 1303. In FIG. 1B, the pixel electrode 1301 is an electrode that reflects visible light. When the pixel electrode 1301 reflects visible light, the pixel electrode 1301 is visually recognized as a black display when the liquid crystal layer 1303 is on.

  The light receiving element 1201 has light receiving sensitivity at least in the infrared wavelength region. The liquid crystal display device can capture an image using infrared rays detected by the light receiving element 1201.

  Here, light that has entered the liquid crystal display device from the second substrate 1013 side is incident on the light receiving element 1201. In the configuration according to this embodiment, a liquid crystal layer 1303 is disposed on the viewing side of the light receiving element 1201. In the case where an electric field is not formed in the liquid crystal layer 1303 (in the off state), visible light is scattered by liquid crystal molecules dispersed in the polymer material and is not easily incident on the light receiving element 1201.

  On the other hand, infrared rays can pass through the polymer dispersed liquid crystal material. Therefore, by providing the light receiving element 1201 having light receiving sensitivity in the infrared wavelength region, the light receiving element 1201 can detect infrared light regardless of whether or not the liquid crystal layer 1303 has an electric field. And it can image using the infrared rays which the light receiving element 1201 detected.

  Note that the liquid crystal display device according to this embodiment can detect and image an object to be detected located on the liquid crystal layer 1303 side. Light enters the liquid crystal display device from the liquid crystal layer 1303 side. Light (infrared rays) incident on the liquid crystal display device does not reach the light receiving element 1201 when blocked by the detection object. As a result, the shadow of the detected object is recognized using the light receiving element 1201, and the detected object can be imaged.

  When a liquid crystal layer is formed using a polymer-dispersed liquid crystal material as in this embodiment mode, a polarizing plate and an alignment film are unnecessary, and thus light loss due to light absorption by the polarizing plate and the alignment film is eliminated, and a bright display is achieved. It can be performed. For this reason, bright white display is possible, and display close to the paper surface by the display device can be achieved. Note that the display close to the paper surface means that the hue, brightness, or reflectance is close to the actual paper surface.

  Then, as in this embodiment, by providing a light receiving element having light receiving sensitivity in the infrared wavelength region as a light receiving element for imaging, imaging is performed with infrared light that can pass through a liquid crystal layer using a polymer dispersed liquid crystal material. can do. By using a light receiving element having light receiving sensitivity in the infrared wavelength region, it is possible to prevent light reception failure due to scattering of incident light peculiar to a polymer dispersed liquid crystal material, and high-accuracy imaging can be performed.

  In addition, since a polymer-dispersed liquid crystal material is used, a polarizing plate and an alignment film are unnecessary, and further a rubbing process and the like are unnecessary. Therefore, manufacturing members and manufacturing processes can be reduced, and costs can be reduced and productivity can be improved. In addition, since the liquid crystal display device according to this embodiment is a reflective liquid crystal display device, a backlight is unnecessary, which can also lead to reduction of members and cost reduction. In addition, since the number of members can be reduced as described above, it can also contribute to thinning.

  Note that FIGS. 1A and 1B illustrate an example in which one pixel 1000 includes one photosensor 1200 and one display element 1100; however, one embodiment of the present invention is limited to this. Instead, one photosensor may be provided for each of a plurality of pixels.

  Next, the structure illustrated in FIG. 1B will be specifically described.

  A light receiving element 1201 and a transistor 1101 are provided over the first substrate 1003 with an insulating layer 1005 interposed therebetween.

  As the first substrate 1003, a substrate that can withstand a later manufacturing process is used. For example, an insulating substrate such as a glass substrate or a quartz substrate, a semiconductor substrate such as a silicon substrate, a flexible substrate such as a plastic substrate, or a conductive substrate such as a stainless steel substrate can be given. Note that the first substrate 1003 is a substrate positioned on the side opposite to the viewing side (second substrate 1013), and thus it is not essential to transmit visible light.

  The light receiving element 1201 and the element such as a transistor constitute the photosensor 1200 in FIG. The transistor 1101 forms the display element 1100 in FIG. 1A together with a structure in which a liquid crystal layer 1303 is sandwiched between the pixel electrode 1301 and the counter electrode 1305 (referred to as a liquid crystal element 1300), other elements, and the like.

  As the light receiving element 1201, an example in which a photodiode, specifically, a lateral pin photodiode is applied is illustrated. Here, a photodiode serving as the light receiving element 1201 includes a region 1203 (also referred to as a p-type semiconductor layer) containing an impurity element imparting p-type conductivity and a region 1205 (also referred to as an i-type semiconductor layer) having intrinsic semiconductor characteristics. And a region including an impurity element imparting n-type conductivity (also referred to as an n-type semiconductor layer).

  In this embodiment, the case where the light receiving element 1201 is a lateral pin photodiode (pin junction) is illustrated, but the light receiving element 1201 may be a pn photodiode (pn junction).

  The light receiving element 1201 can be a vertical photodiode instead of a horizontal photodiode. In this case, a p-type semiconductor layer can be formed by stacking a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer, or a p-type photodiode can be formed by sequentially stacking a p-type semiconductor layer and an n-type semiconductor layer. .

  The material constituting the light receiving element 1201 is not particularly limited as long as it is a material that absorbs infrared rays. For example, microcrystalline silicon, polycrystalline silicon, single crystal silicon, amorphous silicon, or the like can be given. In addition, InGaAs, PbS, PbSe, or the like can be used.

  The transistor 1101 is electrically connected to the pixel electrode 1301 and functions as a driving transistor that drives the liquid crystal element 1300. The transistor 1101 can have a structure, a constituent material, or the like that is appropriately selected depending on the performance desired. For example, a transistor in which a semiconductor layer is formed using amorphous silicon, microcrystalline silicon, polycrystalline silicon, or the like can be used. Alternatively, a transistor in which a semiconductor layer is formed using an oxide semiconductor can be used. Further, any structure of a top gate type in which a gate electrode is arranged on a semiconductor layer and a bottom gate type in which a gate electrode is arranged under a semiconductor layer may be applied. Furthermore, any structure of a top contact type in which a source electrode and a drain electrode are formed on a semiconductor layer and a bottom contact type in which a source electrode and a drain electrode are formed under a semiconductor layer may be applied.

  FIG. 1B illustrates an example in which a top-gate transistor 1101 is provided. Here, the transistor 1101 includes a semiconductor layer including a channel formation region 1103 between a pair of impurity regions 1105 and a gate electrode 1107 provided over the semiconductor layer with an insulating layer 1007 functioning as a gate insulating layer interposed therebetween. , Is composed of. The pair of impurity regions 1105 functions as a source region or a drain region. In addition, a pair of conductive layers 1109 provided in contact holes of the insulating layers 1009 and 1007 are electrically connected to the impurity region 1105 of the transistor 1101. The pair of conductive layers 1109 function as a source electrode or a drain electrode.

  One of the pair of conductive layers 1109 is electrically connected to the pixel electrode 1301 through a contact hole included in the insulating layer 1011. Accordingly, the pixel electrode 1301 and the transistor 1101 are electrically connected.

  The island-shaped semiconductor layer of the transistor 1101 and the island-shaped semiconductor layer of the light-receiving element 1201 are formed by forming a semiconductor layer over the first substrate 1003 with an insulating layer 1005 interposed therebetween, and etching the semiconductor layer by etching or the like. By processing (patterning) into the shape, it can be formed in the same process. Therefore, it is not necessary to add a separate photodiode manufacturing process in addition to the normal panel manufacturing process, and the manufacturing cost can be reduced.

  Note that an insulating layer functioning as a passivation layer or an interlayer insulating layer is formed as appropriate over the light-receiving element 1201 and the transistor 1101. FIG. 1B illustrates an example in which the insulating layer 1009 and the insulating layer 1011 are formed. Note that an insulating layer functioning as a planarization layer is preferably formed below the pixel electrode 1301 in order to keep the cell gap of the liquid crystal layer 1303 uniform. Here, the insulating layer 1011 is formed as a planarization layer.

  A pixel electrode 1301, a liquid crystal layer 1303, and a counter electrode 1305 are provided in this order over the insulating layer 1011. In addition, a second substrate 1013 (also referred to as a counter substrate) provided to face the first substrate 1003 is provided over the counter electrode 1305.

  The pixel electrode 1301 is provided with an electrode that reflects visible light. Specifically, a conductive material such as copper, molybdenum, titanium, chromium, tungsten, aluminum, or silver, or an alloy thereof is used. Preferably, the one with low reflectance is used.

  In addition, there exists a possibility that the electrode which reflects the above visible rays may reflect even infrared rays. Therefore, the pixel electrode 1301 is preferably not provided at a position overlapping the light receiving element 1201 when viewed from above.

  The counter electrode 1305 is provided with an electrode that transmits visible light. Specifically, a light-transmitting conductive material such as indium tin oxide, indium tin oxide containing silicon oxide, organic indium, organic tin, zinc oxide, and indium zinc oxide containing zinc oxide (IZO; Indium) Zinc Oxide), zinc oxide containing gallium, tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, or the like is used. Form.

  The liquid crystal layer 1303 is provided over the entire surface of the first substrate 1003. Therefore, the pixel electrode 1301 is also provided over the insulating layer 1011 that is not provided. The liquid crystal layer 1303 can be formed using the above-described polymer dispersed liquid crystal material by a liquid crystal dropping method or a liquid crystal injection method. In the case of a liquid crystal dropping method, after a liquid crystal material is dropped on the first substrate 1003 provided with the pixel electrode 1301 or the second substrate 1013 provided with the counter electrode 1305, the first substrate 1003 and the second substrate 1003 are dropped. The substrate 1013 may be attached. In the case of the liquid crystal injection method, the first substrate 1003 provided with the pixel electrode 1301 and the second substrate 1013 provided with the counter electrode 1305 are attached to each other, and then the pixel electrode 1301 and the counter electrode 1305 are bonded. A liquid crystal material may be injected between them.

  The liquid crystal layer 1303 includes a polymer dispersed liquid crystal material or a polymer network type liquid crystal material, and the liquid crystal material is dispersed in a polymer (polymer) that forms the polymer network.

  As the liquid crystal material, nematic liquid crystal can be used.

  Moreover, a photocuring resin can be used as the polymer material. As the photocurable resin, a monofunctional monomer such as acrylate or methacrylate, a polyfunctional monomer such as diacrylate, triacrylate, dimethacrylate, or trimethacrylate, or a mixture of these monomers can be used. As the polymer material, a liquid crystal polymer, a non-liquid crystal polymer, or a mixture of a liquid crystal polymer and a non-liquid crystal polymer can be used.

  Moreover, when using a photocurable resin as a polymer material, a photopolymerization initiator is used. And what is necessary is just to select resin hardened | cured with the light of the wavelength which a photoinitiator reacts as photocuring resin. For example, an ultraviolet curable resin can be used as the photocurable resin.

  In addition, as a photoinitiator, the radical polymerization initiator which generate | occur | produces a radical by light irradiation, the acid generator which generates an acid, or the base generator which generates a base can be used.

  The liquid crystal layer 1303 irradiates a liquid crystal material including, for example, a nematic liquid crystal, a monomer or oligomer that is a photocurable resin, and a photopolymerization initiator with a wavelength at which the photocurable resin and the photopolymerization initiator react. By doing so, it can be formed.

  Note that the cell gap of the liquid crystal layer 1303 (the distance between the pixel electrode 1301 and the counter electrode 1305) is preferably controlled by providing a spacer. Examples of the shape of the spacer include a columnar shape and a spherical shape. The practitioner can arbitrarily determine the position where the spacer is provided, the number and density of the spacers, and the like. The spacer may be provided on the counter electrode or the pixel electrode. When the spacer is spherical, it may be dispersed in the liquid crystal layer 1303.

  Since the second substrate 1013 is disposed on the viewing side, a substrate that transmits visible light is used. In addition, in order to cause the light receiving element 1201 to detect infrared rays, a substrate that transmits infrared rays is used. For example, an insulating substrate such as a glass substrate or a quartz substrate, or a flexible substrate such as a plastic substrate can be given.

  Note that although an example in which a thin semiconductor layer is formed over the first substrate 1003 and the light receiving element 1201, the transistor 1101, and the like are formed using the semiconductor layer is described in this embodiment, there is no particular limitation. For example, a semiconductor substrate (single crystal semiconductor substrate), an SOI substrate, or the like can be used, and a light receiving element or an active layer of a transistor may be formed using part of the semiconductor substrate or part of the SOI substrate.

  The structure described in this embodiment can be combined as appropriate with any of the other embodiments and examples in this specification.

(Embodiment 2)
In this embodiment, an example of a liquid crystal display device, which is different from that in the above embodiment, will be described.

  FIG. 2 is a schematic view of a cross section of a liquid crystal display device having a configuration different from that of FIG. 1B between broken lines PQ in FIG. A part of the display element 1100 is shown on the right side of the page from the two-dot chain line in FIG. 2, and a part of the photosensor 1200 is shown on the left side of the page.

  In FIG. 2, the liquid crystal display device includes a liquid crystal layer 2303 and a light receiving element 2201, and the liquid crystal layer 2303 is arranged on the viewing side with respect to the light receiving element 2201.

  The present embodiment is a reflective liquid crystal display device as in the first embodiment, and is visually recognized from the second substrate 2015 side. In addition, the object to be detected on the second substrate 2015 side is imaged.

  The liquid crystal layer 2303 is sandwiched between a counter electrode 2305 disposed on the viewing side and a pixel electrode 2301 disposed to face the counter electrode 2305. The liquid crystal element 2300 includes a liquid crystal layer 2303, a counter electrode 2305, and a pixel electrode 2301.

  The liquid crystal layer 2303 corresponds to the liquid crystal layer 1303 of Embodiment 1 and includes a polymer dispersed liquid crystal material, and the liquid crystal material is dispersed in a polymer material forming a polymer network.

  Here, the difference between the configuration illustrated in FIG. 2 and the configuration illustrated in FIG. 1B is that a pixel electrode 2301 that transmits visible light is provided instead of the pixel electrode 1301 that reflects visible light. The black layer 2403 is disposed on the opposite side of the pixel electrode 2301 from the viewing side.

  The black layer 2403 is formed using, for example, a black organic resin material. Specifically, it can be formed by mixing a pigment-based black resin, carbon black, titanium black, or the like with a resin material such as photosensitive or non-photosensitive polyimide. Alternatively, a light-shielding metal material that absorbs visible light, for example, chromium can be used. However, in the case of a light-shielding metal material, infrared rays may be absorbed, so that it is not disposed on the light receiving element 2201.

  When the liquid crystal layer 2303 is in an off state, the incident light is scattered by the liquid crystal molecules in the polymer material as in the liquid crystal layer 1303 of Embodiment 1, and a white display is visually recognized. On the other hand, when the liquid crystal layer 2303 is in an on state, incident light is transmitted and absorbed by the black layer 2403, and a black display is visually recognized.

  The thickness of the liquid crystal layer 2303 is preferably 5 μm or more and 30 μm or less. By setting it as such a range, power consumption can be suppressed.

  Note that the black layer 2403 may be disposed on the side opposite to the viewing side of the liquid crystal layer 2303. For example, a structure in which a black layer is provided on the substrate on the pixel electrode 2301 side (first substrate 2003), specifically, a structure in which a black layer is provided on a surface opposite to the viewing side of the first substrate 2003 is provided. Also good.

  As shown in FIG. 2, when the black layer 2403 is disposed on the light receiving element 2201, the black layer 2403 absorbs a wavelength (visible light or the like) in a region other than infrared, that is, infrared that selectively transmits infrared. Acts as a transmission filter. Thereby, the detection accuracy of the light receiving element 2201 can be improved.

  In addition to the black layer 2403, an infrared transmission filter may be provided over the light receiving element 2201. In the configuration illustrated in FIG. 1B, an infrared transmission filter may be provided over the light receiving element 1201. With the infrared transmission filter, the detection accuracy of the light receiving element 1201 can be improved even in the configuration shown in FIG.

  Note that when the black layer 2403 is formed of a black organic resin or the like, there is a concern about impurity contamination from the black layer 2403. Therefore, FIG. 2 illustrates an example in which the insulating layer 2401 and the insulating layer 2405 are provided with the black layer 2403 interposed therebetween.

  The light receiving element 2201 corresponds to the light receiving element 1201 of the first embodiment. However, FIG. 2 shows an example in which a vertical pin photodiode is applied instead of the horizontal pin photodiode shown in FIG.

  The configuration in FIG. 2 is different from the configuration in FIG. 1B of the first embodiment in the configuration for making the black display visible. However, since the liquid crystal display device according to this embodiment also does not require a polarizing plate and an alignment film, light loss due to light absorption by the polarizing plate and the alignment film is eliminated, and a bright display can be performed. For this reason, bright white display is possible, and display close to the paper surface by the display device can be achieved. In addition, cost reduction and productivity improvement can be achieved.

  Since a light receiving element having a light receiving sensitivity in the infrared wavelength region is provided as a light receiving element for imaging, it is possible to image with high accuracy even when a polymer dispersed liquid crystal material is used.

  Further, the black layer for black display can function as an infrared transmission filter for the light receiving element. Thereby, it can be tied to still more highly accurate imaging.

  FIG. 2 illustrates an example in which a transistor 2221 a and a transistor 2221 b are arranged in the photosensor 1200 in addition to the light receiving element 2201. In addition, an example in which a storage capacitor 2121 is arranged in the display element 1100 in addition to the transistor 2101 is shown. Further, FIG. 2 illustrates an example in which a transistor structure different from that in FIG.

  FIG. 2 shows an example of a top-gate transistor structure in which a gate electrode is provided above a semiconductor layer and a conductive layer functioning as a source or drain is provided on the semiconductor layer. Of course, a bottom gate type structure in which a gate electrode is provided below the semiconductor layer may be applied, or a bottom contact type structure in which a conductive layer functioning as a source or drain is provided below the semiconductor layer may be applied. Good.

  FIG. 2 shows an example having one photosensor 1200 and one display element 1100. The photosensor 1200 may be provided for each pixel or may be provided for each of a plurality of pixels.

  Next, the configuration shown in FIG. 2 will be specifically described. Note that description of the same structure as that in FIG.

  Over the first substrate 2003, a light receiving element 2201, a transistor 2221a, a transistor 2221b, a transistor 2101, and a storage capacitor 2121 are provided with an insulating layer 2005 interposed therebetween.

  The first substrate 2003 and the insulating layer 2005 correspond to the first substrate 1003 and the insulating layer 1005 in Embodiment Mode 1.

  In the light receiving element 2201, an n-type semiconductor layer 2203, an i-type semiconductor layer 2204, and a p-type semiconductor layer 2205 are sequentially stacked. In addition, a wiring 2211 and a wiring 2213 that are electrically connected to the light receiving element 2201 are provided. The wiring 2211 functions as a signal wiring on the scanning line side. The wiring 2213 electrically connects the light receiving element 2201 and the transistor 2221a.

  The transistor 2221a includes a semiconductor layer 2223a, a pair of conductive layers 2224a provided over the semiconductor layer 2223a, and a gate electrode 2225a provided over the semiconductor layer 2223a with an insulating layer 2007 interposed therebetween. . The pair of conductive layers 2224a function as a source or a drain.

  The transistor 2221b includes a semiconductor layer 2223b, a pair of conductive layers 2224b provided over the semiconductor layer 2223b, and a gate electrode 2225b provided over the semiconductor layer 2223b with an insulating layer 2007 interposed therebetween. . The pair of conductive layers 2224b function as a source or a drain.

  Note that here, the other of the pair of conductive layers 2224a of the transistor 2221a and the one of the pair of conductive layers 2224b of the transistor 2221b are provided with a common conductive layer, which is electrically connected.

  The transistor 2101 includes a semiconductor layer 2103, a pair of conductive layers 2104 provided over the semiconductor layer 2103, and a gate electrode 2105 provided over the semiconductor layer 2103 with an insulating layer 2007 interposed therebetween. . The pair of conductive layers 2104 function as a source or a drain.

  The storage capacitor 2121 includes a first electrode 2124 and a second electrode 2125 provided over the first electrode 2124 with an insulating layer 2007 interposed therebetween.

  The insulating layer 2007 functions as a gate insulating layer of the transistors 2221a, 2221b, and 2101 and functions as a dielectric layer of the storage capacitor 2121.

  The transistor in this embodiment can be selected as appropriate by the practitioner as to the structure, constituent materials, and the like of the transistor as in Embodiment 1. For example, an oxide semiconductor layer can be used as the semiconductor layer 2223a of the transistor 2221a, the semiconductor layer 2223b of the transistor 2221b, and the semiconductor layer 2103 of the transistor 2101 which are illustrated in FIGS.

For example, the oxide semiconductor layer includes an In—Sn—Ga—Zn—O system that is a quaternary metal oxide, an In—Ga—Zn—O system that is a ternary metal oxide, and In—Sn—Zn. -O-based, In-Al-Zn-O-based, Sn-Ga-Zn-O-based, Al-Ga-Zn-O-based, Sn-Al-Zn-O-based, and binary metal oxide In -Zn-O, Sn-Zn-O, Al-Zn-O, Zn-Mg-O, Sn-Mg-O, In-Mg-O, In-Ga-O, In It is formed using an oxide semiconductor such as an —O-based, Sn—O-based, or Zn—O-based semiconductor. Here, for example, an In—Ga—Zn—O-based oxide semiconductor is an oxide containing at least In, Ga, and Zn, and there is no particular limitation on the composition ratio thereof. Moreover, elements other than In, Ga, and Zn may be included. The oxide semiconductor may contain SiO ₂ .

The oxide semiconductor layer can be formed using an oxide semiconductor represented by the chemical formula, InMO ₃ (ZnO) _m (m> 0). Here, M represents one metal element selected from Ga, Al, Mn, or Co, or a plurality of metal elements. For example, M includes Ga, Ga and Al, Ga and Mn, or Ga and Co.

  Note that the oxide semiconductor layer is preferably formed by a sputtering method. For example, it is formed by a sputtering method using the above-described oxide target.

  In addition, as an oxide semiconductor layer, hydrogen that is an n-type impurity is removed from the oxide semiconductor and purified so that impurities other than the main component of the oxide semiconductor are included as much as possible, whereby i-type (intrinsic) An oxide semiconductor layer or an oxide semiconductor layer close to i-type (intrinsic) can be used. That is, it is possible to apply a highly purified i-type (intrinsic) or an oxide semiconductor layer close thereto by removing impurities as much as possible, such as hydrogen and water, instead of adding an impurity to make it i-type. it can.

Note that the highly purified oxide semiconductor layer has very few carriers (near zero), and the carrier concentration is less than 1 × 10 ¹⁴ / cm ³ , preferably less than 1 × 10 ¹² / cm ³ , more preferably It is less than 1 × 10 ¹¹ / cm ³ .

  Since the number of carriers in the oxide semiconductor layer is extremely small, off-state current can be reduced in the off-state characteristics of the transistor (that is, in the case of an n-channel transistor, in which the source potential is higher than or equal to the gate potential).

Specifically, the transistor including the above-described highly purified oxide semiconductor layer has a current value in an off state (off-state current value) of 10 aA / μm (1 × 10 ⁻¹⁷ A / μm) or less, and further 1 aA / Μm (1 × 10 ⁻¹⁸ A / μm) or less, and further to a level of 10 zA / μm (1 × 10 ⁻²⁰ A / μm) or less.

  By using a transistor including such a purified oxide semiconductor, off-state current can be extremely reduced. Therefore, leakage in the photosensor can be suppressed, and the imaging accuracy can be improved.

  Note that in the case where a transistor including an oxide semiconductor layer is used, it is preferable that an insulating layer or the like contain as little hydrogen or water as possible.

  An insulating layer 2009 and an insulating layer 2011 are provided over the light-receiving element 2201, the transistor 2221 a, the transistor 2221 b, the transistor 2101, and the storage capacitor 2121.

  A wiring 2213 that electrically connects the light-receiving element 2201 and the transistor 2221a is provided through a contact hole that penetrates the insulating layers 2009 and 2011. FIG. 2 illustrates an example in which the wiring 2213 and the p-type semiconductor layer 2205 of the light receiving element 2201 are electrically connected, and the wiring 2213 and the gate electrode 2225a of the transistor 2221a are electrically connected.

  In addition, a wiring 2111 electrically connected to the transistor 2101 is provided through a contact hole penetrating the insulating layer 2007, the insulating layer 2009, and the insulating layer 2011. The wiring 2111 functions as a connection wiring that electrically connects the pixel electrode 2301 and the transistor 2101.

  An insulating layer 2013 is provided over the wiring 2213, the wiring 2111, and the insulating layer 2011. A black layer 2403 is provided over the insulating layer 2013 with the insulating layer 2401 interposed therebetween, and a pixel electrode 2301 is provided with the insulating layer 2405 interposed therebetween. The pixel electrode 2301 is electrically connected to the wiring 2111 through a contact hole that penetrates the insulating layer 2405, the black layer 2403, the insulating layer 2401, and the insulating layer 2013.

  The insulating layer 2005, the insulating layer 2007, the insulating layer 2009, the insulating layer 2011, and the insulating layer 2013 are each formed using a material or the like as a blocking layer, a gate insulating layer, a passivation layer, an interlayer insulating layer, or a planarization layer that diffuses impurities. Select and form. Note that in the case where an oxide semiconductor layer is used for the transistor, it is preferable that hydrogen or water be not contained as much as possible.

  The pixel electrode 2301 is provided with an electrode that transmits visible light. Specifically, a light-transmitting conductive material such as indium tin oxide, indium tin oxide containing silicon oxide, organic indium, organic tin, zinc oxide, and indium zinc oxide containing zinc oxide (IZO; Indium) Zinc Oxide), zinc oxide containing gallium, tin oxide, indium oxide containing tungsten oxide, indium zinc oxide containing tungsten oxide, indium oxide containing titanium oxide, indium tin oxide containing titanium oxide, or the like is used. Form.

  The liquid crystal layer 2303, the counter electrode 2305, and the second substrate 2015 correspond to the liquid crystal layer 1303, the counter electrode 1305, and the second substrate 1013 in Embodiment Mode 1.

  Note that although an example in which a thin semiconductor layer is formed over the first substrate 2003 and a transistor is formed using the semiconductor layer is described in this embodiment, the present invention is not particularly limited, and a semiconductor substrate or an SOI substrate is used. It may be used to form a transistor. 2 can be applied to the transistor shown in FIG. 1B, or the transistor shown in FIG. 2 can be applied to FIG. 1B.

  The structure described in this embodiment can be combined as appropriate with any of the other embodiments and examples in this specification.

(Embodiment 3)
A configuration of the liquid crystal display device will be described with reference to a schematic diagram of an upper surface of FIG. The liquid crystal display device 301 includes a pixel array 311, a first control circuit unit 331, and a second control circuit unit 341.

  The pixel array 311 includes a plurality of pixels 321 arranged in a matrix in the row direction and the column direction. The pixel 321 includes a display element 323 and a photosensor 325. A photo sensor 325 is used to detect and image an object to be detected that touches or approaches the liquid crystal display device 301, specifically, the pixel array 311.

  FIG. 3 illustrates an example in which each pixel 321 includes one display element 323 and one photosensor 325, but it is not necessary that all the pixels include the photosensor 325. The practitioner can appropriately select the necessary number and arrangement. For example, one photosensor can be provided for each of a plurality of pixels, and one photosensor can be provided for every four pixels as an example.

  The liquid crystal display device 301 can capture an image using infrared rays detected by the photosensor 325. Specifically, in the liquid crystal display device 301, whether the external light is blocked by the detection target due to the infrared rays detected by the photosensor 325 and a shadow is formed on the pixel array 311, or the external light is incident on the pixel array 311. It is possible to determine whether the object has been detected and to detect and image an object to be detected.

  The photosensor 325 includes at least a light receiving element having light receiving sensitivity in an infrared wavelength region. In addition to the light receiving element, it includes a transistor.

  The display element 323 includes a transistor, a storage capacitor, a liquid crystal element, and the like. The liquid crystal element has a liquid crystal layer.

  The transistor in the display element 323 has a function of controlling injection of charge into the storage capacitor or discharge of charge from the storage capacitor. The storage capacitor has a function of holding a charge corresponding to a voltage applied to the liquid crystal layer.

  The liquid crystal display device 301 according to this embodiment uses a polymer-dispersed liquid crystal material for a liquid crystal layer. Therefore, the liquid crystal display device 301 according to the present embodiment performs white display (bright display) using scattered light from the liquid crystal material and performs black display (dark display) using light transmitted through the liquid crystal material. The image is displayed.

  The first control circuit portion 331 is a circuit for controlling the photosensor 325 and includes a readout circuit 333 on the signal line side and a photosensor drive circuit 335 on the scanning line side. The photo sensor driving circuit 335 on the scanning line side has a function of performing a reset operation and a selection operation described later on the photo sensor 325 included in the pixel 321 arranged in a specific row. Further, the reading circuit 333 on the signal line side has a function of taking out an output signal of the photosensor 325 included in the pixel 321 in the selected row. Note that the readout circuit 333 on the signal line side outputs a photosensor output that is an analog signal to the outside of the liquid crystal display device as an analog signal using an OP amplifier, or a digital signal using an A / D conversion circuit. A configuration that can be taken out of the liquid crystal display device after conversion is conceivable.

  The second control circuit unit 341 is a circuit for controlling the display element 323. The second control circuit portion 341 includes a display element driver circuit 345 that inputs a signal to the display element 323 through a signal line such as a video data signal line (also referred to as a “source signal line”), and a scanning line (“gate signal”). A display element driver circuit 343 which inputs a signal to the display element 323 through a line. For example, the display element driver circuit 343 has a function of selecting display elements included in pixels arranged in a specific row. The display element driver circuit 345 has a function of applying an arbitrary potential to the display elements included in the pixels in the selected row. Note that in a display element to which a high potential (a “high level” potential) is applied by the display element driver circuit 343, the transistor is turned on, and the charge supplied from the display element driver circuit 345 is supplied.

  Next, a circuit diagram of the pixel 321 in the pixel array 311 will be described with reference to FIG. The pixel 321 includes a display element 323 including a transistor 421, a storage capacitor 423, and a liquid crystal element 425, and a photosensor 325 including a photodiode 437 as a light receiving element, a transistor 431, and a transistor 433. Each pixel 321 includes a first wiring 401 electrically connected to the display element driving circuit 343 on the scanning line side and a second wiring electrically connected to the photo sensor driving circuit 335 on the scanning line side. 403, a third wiring 405, a fourth wiring 411 electrically connected to the display element driver circuit 345 on the signal line side, and a fifth wiring electrically connected to the readout circuit 333 on the signal line side 413 and a sixth wiring 415.

  In the transistor 421, the gate is electrically connected to the first wiring 401, one of the source and the drain is electrically connected to the fourth wiring 411, and the other of the source and the drain is electrically connected to one electrode of the storage capacitor 423 and one electrode of the liquid crystal element 425. It is connected to the. The other electrode of the storage capacitor 423 is kept at a constant potential. The other electrode of the liquid crystal element 425 is kept at a constant potential. The liquid crystal element 425 is an element having a liquid crystal layer containing a polymer dispersed liquid crystal material sandwiched between a pair of electrodes.

  When “H” is applied to the first wiring 401, the transistor 421 applies the potential of the fourth wiring 411 to the storage capacitor 423 and the liquid crystal element 425. The storage capacitor 423 holds the applied potential. The liquid crystal element 425 is turned on to transmit light according to the applied potential.

  In the photodiode 437, one electrode is electrically connected to the second wiring 403 and the other electrode is electrically connected to the gate of the transistor 431. Here, a wiring that electrically connects the photodiode 437 and the gate of the transistor 431 is a seventh wiring 435. In the transistor 431, one of a source and a drain is electrically connected to the fifth wiring 413, and the other of the source and the drain is electrically connected to one of the source and the drain of the transistor 433. The transistor 433 has a gate electrically connected to the third wiring 405 and the other of the source and the drain electrically connected to the sixth wiring 415.

  Next, the structure of the reading circuit 333 will be described with reference to FIG. The read circuit 333 is provided for each column, for example. In FIG. 5, the readout circuit 333 for one column of pixels includes a p-type transistor 453 and a storage capacitor 455. In addition, the pixel line includes a sixth wiring 415, an eighth wiring 461, and a ninth wiring 463.

  In the p-type transistor 453, the gate is electrically connected to the eighth wiring 461, one of the source and the drain is electrically connected to the sixth wiring 415 and one electrode of the storage capacitor 455, and the other of the source or drain is electrically connected to the ninth wiring 463. It is connected to the. The holding capacitor 455 has the other electrode grounded.

  The eighth wiring 461 is a wiring for precharging the sixth wiring 415 prior to the reading operation of the photosensor 325.

  In the reading circuit 333, the potential of the sixth wiring 415 is set to a reference potential before the reading operation of the photosensor 325 in the pixel 321. In FIG. 5, by setting the potential of the eighth wiring 461 to “L”, the sixth wiring 415 can be set to a high potential which is a reference potential. The storage capacitor 455 is not necessarily provided when the parasitic capacitance of the sixth wiring 415 is large. Note that the reference potential may be a low potential. In this case, by using an n-type transistor instead of the p-type transistor 453 and setting the potential of the eighth wiring 461 to “H”, the sixth wiring 415 can be set to a low potential which is a reference potential. .

  Next, a reading operation of the photosensor 325 in the pixel array 311 is described with reference to a timing chart in FIG. In the timing chart of FIG. 6, a signal corresponding to the potential of the second wiring 403, a signal corresponding to the potential of the third wiring 405, a signal corresponding to the potential of the seventh wiring 435, A signal corresponding to the potential of the wiring 415 and a signal corresponding to the eighth wiring 461 are shown.

  Prior to the time point A, when the potential of the eighth wiring 461 is set to “L”, the potential of the sixth wiring 415 is precharged to “H” (precharge operation).

  In the period AB, when the potential of the second wiring 403 is “H”, the photodiode 437 is turned on, and the potential of the seventh wiring 435 to which the gate of the transistor 431 is electrically connected becomes “H” ( Reset operation).

  In the period BC, when the potential of the second wiring 403 is set to “L”, the potential of the seventh wiring 435 to which the gate of the transistor 431 is connected starts to decrease due to the off-state current of the photodiode 437. Since the off-state current of the photodiode 437 increases when irradiated with light, the potential of the seventh wiring 435 to which the gate of the transistor 431 is connected changes in accordance with the amount of irradiated light. That is, the current between the source and drain of the transistor 431 changes (accumulation operation).

  In the period CD, when the potential of the third wiring 405 is set to “H”, the transistor 433 is turned on, and the fifth wiring 413 and the sixth wiring 415 are turned on through the transistor 431 and the transistor 433. Then, the potential of the sixth wiring 415 is decreased. Note that before the time point C, the potential of the eighth wiring 461 is set to “H”, and the precharge of the sixth wiring 415 is completed. Here, the speed at which the potential of the sixth wiring 415 decreases depends on the current between the source and the drain of the transistor 431. That is, it changes in accordance with the amount of light applied to the photodiode 437 (selection operation).

  When the potential of the third wiring 405 is set to “L” at the time D, the transistor 433 is cut off, and the potential of the sixth wiring 415 becomes a constant value after the time D. Here, the constant value is determined according to the amount of light applied to the photodiode 437. Therefore, by acquiring the potential of the sixth wiring 415, the amount of light applied to the photodiode 437 can be known.

  As described above, the reading operation of the photosensor 325 of each pixel 321 is realized by repeating the reset operation, the accumulation operation, and the selection operation. In the liquid crystal display device, the detection object that is in contact with or close to the pixel array 311 can be imaged by executing the reset operation, the accumulation operation, and the selection operation of the photosensor in each pixel.

  By providing a liquid crystal element using a polymer-dispersed liquid crystal material as in this embodiment mode, bright display can be performed and display close to paper can be achieved. In addition, by providing a light receiving element having a light receiving sensitivity in the infrared wavelength region as a light receiving element of the photosensor, light reception failure due to scattering of incident light in a state where no electric field peculiar to the polymer dispersed liquid crystal material is applied is prevented. Can be taken with high accuracy.

  The structure described in this embodiment can be combined as appropriate with any of the other embodiments and examples in this specification.

(Embodiment 4)
In this embodiment, examples of circuit diagrams applicable to a photosensor will be described with reference to FIGS. The photosensor described in this embodiment can be applied instead of the photosensor 325 illustrated in FIG.

  FIG. 7A illustrates a structure including a transistor 231 and a tenth wiring 232 in addition to the photosensor 325 illustrated in FIG. In the transistor 231, the gate is electrically connected to the tenth wiring 232, one of the source and the drain is electrically connected to the other electrode of the photodiode 437, and the other of the source and the drain is electrically connected to the gate of the transistor 431. Connected. The transistor 231 has a function of holding charge accumulated in the gate of the transistor 431.

  FIG. 7B illustrates a structure in which the storage capacitor 233 and the eleventh wiring 234 are included in addition to the photosensor 325 illustrated in FIG. 4 and the transistor 433 and the third wiring 405 are not included. The storage capacitor 233 has one electrode electrically connected to the other electrode of the photodiode 437 and the other electrode electrically connected to the eleventh wiring 234. In addition, one of the source and the drain of the transistor 431 is electrically connected to the sixth wiring 415.

  FIG. 8A illustrates a structure including a transistor 241 and a twelfth wiring 242 in addition to the photosensor illustrated in FIG. The gate of the transistor 241 is electrically connected to the twelfth wiring 242, one of the source and the drain is electrically connected to the other of the source and the drain of the transistor 231 and the gate of the transistor 431, and the other of the source and the drain is connected The fifth wiring 413 and the transistor 431 are electrically connected to one of a source and a drain. The transistor 241 has a function of supplying a reset signal to the gate of the transistor 431.

  FIG. 8B has a structure in which the connection relationship between the transistor 431 and the transistor 433 is different in the photosensor illustrated in FIG. The transistor 431 has a gate electrically connected to the other of the source and drain of the transistor 231 and one of the source and drain of the transistor 241, and one of the source and drain is electrically connected to one of the source and drain of the transistor 433. The other of the source and the drain is electrically connected to the sixth wiring 415. The other of the source and the drain of the transistor 433 is electrically connected to the other of the fifth wiring 413 and the source or the drain of the transistor 241.

  FIG. 9A illustrates a structure in which the photosensor illustrated in FIG. 8A does not include the transistor 433 and the third wiring 405. The other of the source and the drain of the transistor 431 is electrically connected to the sixth wiring 415.

  FIG. 9B has a structure in which the connection relation between the transistor 241 and the transistor 431 is different in the photosensor illustrated in FIG. The other of the source and the drain of the transistor 241 is electrically connected to the thirteenth wiring 244. In the transistor 431, one of a source and a drain is electrically connected to the fifth wiring 413, and the other of the source and the drain is electrically connected to the sixth wiring 415.

  FIG. 9C has a structure in which the connection relation between the transistor 241 and the transistor 431 is different in the photosensor illustrated in FIG. In the transistor 241, the other of the source and the drain is electrically connected to the other of the source and the drain of the transistor 231 and the gate of the transistor 431. One of the source and the drain is the other of the source and the drain of the transistor 431 and the sixth wiring 415. Is electrically connected.

  As described above, various circuit configurations can be applied to the photosensor. Of course, as the light receiving element constituting the photosensor, an element having light receiving sensitivity in the infrared wavelength region is applied. A liquid crystal display device provided with such a photosensor can capture images with high accuracy.

  The structure described in this embodiment can be combined as appropriate with any of the other embodiments and examples in this specification.

(Embodiment 5)
In this embodiment, application examples of the liquid crystal display device described in the above embodiment will be described.

  FIG. 10 illustrates an example of a writing board (also referred to as a blackboard or a whiteboard) in which the liquid crystal display device described in the above embodiment is incorporated. For example, the liquid crystal display device described in the above embodiment can be incorporated in the panel portion 9696 of the writing board 9600.

  Writing can be freely performed on the surface of the panel portion 9696 using a marker or the like. A glass substrate or a transparent synthetic resin sheet can be used for the surface of the panel portion 9696.

  A liquid crystal display device incorporated in the panel portion 9696 includes a light receiving element having light receiving sensitivity in an infrared wavelength region in a pixel, and can capture an image. Therefore, by connecting the writing board 9600 to a printer or the like, it is possible to read and print characters and drawings written in the panel portion 9696. Of course, the writing board 9600 main body may have a printer.

  In addition, the liquid crystal display device having the display function and the imaging function according to the above embodiment is incorporated in the panel portion 9696, and an image is displayed. Further, characters and figures written on the surface of the panel portion 9696 with a marker or the like are displayed. Can be imaged and read. In addition, characters and diagrams can be written on the panel portion 9696 in a state where an image is displayed, and the locus of the marker that has been captured and read and the image can be combined and displayed. A display image of the panel portion 9696, written characters, and the like can be printed by a printer or the like.

  By applying the liquid crystal display device described in the above embodiment, a white board can make it easy to see a display close to a paper surface, particularly a white display. In addition, by adopting a configuration in which imaging is performed using infrared rays, even a liquid crystal display device to which a polymer-dispersed liquid crystal material is applied can perform imaging with high accuracy.

  Next, FIG. 11 illustrates an example of a portable information terminal in which the liquid crystal display device described in the above embodiment is incorporated. FIG. 11 illustrates an example of a portable information terminal that can be used as an electronic book terminal.

  A portable information terminal 4700 illustrated in FIG. 11A includes two housings, a first housing 4701 and a second housing 4703. In addition, the first housing 4701 is provided with a power supply 4721, a speaker 4725, and the like. The first housing 4701 and the second housing 4703 are integrated with a shaft portion 4711 and can be opened and closed with the shaft portion 4711 as an axis. With such a configuration, it can be handled like a book printed on paper.

  A first panel portion 4705 is incorporated in the first housing 4701. A second panel portion 4707 is incorporated in the second housing 4703. The first panel unit 4705 and the second panel unit 4707 may be configured to display subsequent images or may be configured to display different images. By adopting a configuration in which different images are displayed, for example, text is displayed on the right panel (the first panel 4705 in FIG. 11A) with respect to the page, and the left panel (see FIG. 11). 11 (B), an illustration can be displayed on the second panel portion 4707).

  A liquid crystal display device including the display function and the imaging function according to the above embodiment is incorporated in the first panel portion 4705 and / or the second panel portion 4707. An operation key is displayed on the panel unit together with an image. And it can be set as the structure which detects that a user touched the operation key (imaging), and sends a page.

  In addition, a character or a figure is written with a finger or a pen tip in a state where an image is displayed on the first panel unit 4705 and / or the second panel unit 4707, and the trajectory read by imaging is combined with the image. It can also be displayed.

  Note that a keyboard, a pointing device, or the like may be provided on the same surface as the panel portion of the housing. Further, an external connection terminal (such as an earphone terminal, a USB terminal, or a terminal that can be connected to various types of cables such as an AC adapter and a USB cable), a recording medium insertion unit, and the like may be provided on the back and side surfaces of the housing. . Further, the portable information terminal 4700 may have a configuration having an electronic dictionary function.

  Further, the portable information terminal 4700 may be configured to transmit and receive information wirelessly. It is also possible to adopt a configuration in which desired book data or the like is purchased and downloaded from an electronic book server wirelessly.

  Next, an example of a portable information terminal having a configuration different from that in FIG. 11A is illustrated in FIGS.

  A portable information terminal 4300 illustrated in FIGS. 11B and 11C is an example of a flexible terminal. FIG. 11B shows a state where the portable information terminal 4300 is opened, and FIG. 11C shows a state where the portable information terminal 4300 is closed.

  The portable information terminal 4300 includes three housings, a first housing 4305, a second housing 4306, and a third housing 4313. The first housing 4305, the second housing 4306, and the third housing 4313 are integrated with a shaft portion 4308. The third housing 4313 is inserted between the first housing 4305 and the second housing 4306. The first housing 4305, the second housing 4306, and the third housing 4313 can perform an opening / closing operation and a page turning operation with the shaft portion 4308 as an axis. With such a configuration, it can be used as if reading an actual book.

  A first panel portion 4301 is incorporated in the first housing 4305. A second panel portion 4307 is incorporated in the second housing 4306. A third panel portion 4302 is incorporated on one surface of the third housing 4313, and a fourth panel portion 4310 is incorporated on the other surface. The third housing 4313 includes a third panel portion 4302 and a fourth panel portion 4310 so that double-sided display can be performed. In the case where the portable information terminal 4300 illustrated in FIG. 11B is used as left-binding, pages of the first panel portion 4301, the third panel portion 4302, the fourth panel portion 4310, and the second panel portion 4307 In the case of right binding, the pages are in reverse order.

  A first housing 4305 in which the first panel portion 4301 is incorporated, a second housing 4306 in which the second panel portion 4307 is incorporated, and a third panel portion 4302 and a fourth panel portion 4310 are incorporated. The third housing 4313 is flexible and has high flexibility. In addition, when a plastic substrate is used for the first housing 4305 and the second housing 4306 and a thin film is used for the third housing 4313, the portable information terminal 4300 is thin and can be used like a book. It can be.

  Note that the third housing 4313 may be omitted to be a spread-type terminal, or a third housing may be added to increase the number of pages.

  A liquid crystal display device provided with the display function and the imaging function according to any of the above embodiments in the first panel portion 4301, the second panel portion 4307, the third panel portion 4302, and / or the fourth panel portion 4310. Incorporated. An operation key (the operation key 4304 is displayed on the first panel portion 4301 in FIG. 11B) is displayed on the panel portion together with the image. And it can be set as the structure which detects that a user touched the operation key (imaging), and sends a page.

  In addition, a character or a figure with a finger or a nib in a state where an image is displayed on the first panel portion 4301, the second panel portion 4307, the third panel portion 4302, and / or the fourth panel portion 4310. It is also possible to combine and display a trajectory and an image that are written and imaged and read.

  By applying the liquid crystal display device shown in the above embodiment mode to the portable information terminal shown in FIG. 11, when reading a book such as a newspaper or a paperback, it is possible to perform a display close to a paper surface, particularly a white display. Can make it easier to see. In addition, by adopting a configuration in which imaging is performed using infrared rays, even a liquid crystal display device to which a polymer-dispersed liquid crystal material is applied can perform imaging with high accuracy.

  Although an example in which the liquid crystal display device disclosed in this specification is applied to a writing board or a portable information terminal is described in this embodiment, the present invention can also be applied to other various electronic devices. For example, a display device such as a display, a notebook personal computer, and an image playback device including a recording medium (typically a device having a display that can play back a recording medium such as a DVD: Digital Versatile Disc and display the image) Is mentioned. In addition, mobile phones, portable game machines, video cameras, digital still cameras, goggles type displays (head mounted displays), navigation systems, sound playback devices (car audio, digital audio players, etc.), copiers, facsimiles, printers, printers Examples include multifunction peripherals, automatic teller machines (ATMs), and vending machines. It can also be used for advertisements and posters on vehicles such as trains.

  The structure described in this embodiment can be combined as appropriate with any of the other embodiments and examples in this specification.

  In this example, the results of measuring the wavelength dispersion characteristics of transmittance in a polymer-dispersed liquid crystal material will be described.

  As a measurement sample, a liquid crystal cell having a pixel area of 23 mm × 24 mm was produced. The liquid crystal cell was configured such that only the liquid crystal layer was sandwiched between the quartz substrate and the quartz substrate. The cell gap was produced with the aim of 10 μm.

  The liquid crystal layer is composed of (A) liquid crystal material (trade name MLC-2062, manufactured by Merck & Co., Ltd.), (B) first monomer material (trade name DCP-A (hydrogenated dicyclo), as shown in Table 1 below. Pentadienyl diacrylate)), (C) second monomer material (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name NK ester S-1800A (isostearyl acrylate)), (D) polymerization initiator (trade name, manufactured by Ciba Japan) Irgacure 651 (benzyldimethyl ketal)) was prepared.

  Specifically, (A) liquid crystal material: 376.63 mg, (B) first monomer material: 75.77 mg, (C) second monomer material: 54.32 mg, (D) polymerization initiator: 2.71 mg. A liquid crystal layer containing (A) 73.93 wt%, (B) 14.87 wt%, (C) 10.66 wt%, and (D) 0.53 wt% was formed.

  FIG. 12 shows the results of measurement with a spectrophotometer (“Hitachi Spectrophotometer U-4100” manufactured by Hitachi High-Tech). From FIG. 12, it was confirmed that the measurement sample of this example had an increase in transmittance toward the longer wavelength side from 500 nm, and had a good transmittance in the infrared wavelength region. Note that measurement noise appears in the vicinity of a wavelength of 2600 nm to 2900 nm.

  This example can be implemented in combination with any of the structures described in the other embodiments as appropriate.

231 transistor 232 wiring 233 storage capacitor 234 wiring 241 transistor 242 wiring 244 wiring 301 liquid crystal display device 311 pixel array 321 pixel 323 display element 325 photosensor 331 control circuit section 333 circuit 335 photosensor driving circuit 341 control circuit section 343 display element driving circuit 345 Display element driving circuit 401 Wiring 403 Wiring 405 Wiring 411 Wiring 413 Wiring 415 Wiring 421 Transistor 423 Retention capacitance 425 Liquid crystal element 431 Transistor 433 Transistor 435 Wiring 437 Photo diode 453 P-type transistor 455 Retention capacitance 461 Wiring 463 Wiring 1000 Pixel 1003 Substrate 1005 Insulating layer 1007 Insulating layer 1009 Insulating layer 1011 Insulating layer 1013 Substrate 1100 Display element 1101 Transistor 103 Channel formation region 1105 Impurity region 1107 Gate electrode 1109 Conductive layer 1200 Photosensor 1201 Light receiving element 1203 Region 1205 Region 1207 Region 1300 Liquid crystal element 1301 Pixel electrode 1303 Liquid crystal layer 1305 Counter electrode 2003 Substrate 2005 Insulating layer 2007 Insulating layer 2009 Insulating layer 2011 Insulating Layer 2013 insulating layer 2015 substrate 2101 transistor 2103 semiconductor layer 2104 conductive layer 2105 gate electrode 2111 wiring 2121 storage capacitor 2124 electrode 2125 electrode 2201 light receiving element 2203 n-type semiconductor layer 2204 i-type semiconductor layer 2205 p-type semiconductor layer 2211 wiring 2213 wiring 2221a transistor 2221b Transistor 2223a Semiconductor layer 2223b Semiconductor layer 2224a Conductive layer 2224b Conductive layer 222 a gate electrode 2225b gate electrode 2300 liquid crystal element 2301 pixel electrode 2303 liquid crystal layer 2305 counter electrode 2401 insulating layer 2403 black layer 2405 insulating layer 4300 portable information terminal 4301 panel unit 4302 panel unit 4304 operation key 4305 casing 4306 casing 4307 panel unit 4308 Shaft portion 4310 Panel portion 4313 Case 4700 Portable information terminal 4701 Case 4703 Case 4705 Panel portion 4707 Panel portion 4711 Shaft portion 4721 Power supply 4725 Speaker 9600 Writing board 9696 Panel portion

Claims (6)

It has a display function and an imaging function,
A liquid crystal layer and a light receiving element;
The liquid crystal layer is disposed on the viewing side from the light receiving element, and includes a polymer dispersed liquid crystal material,
The light receiving element has a light receiving sensitivity in an infrared wavelength region,
A liquid crystal display device comprising a function of imaging infrared rays detected by the light receiving element. It has a display function and an imaging function,
A counter electrode, a pixel electrode, a liquid crystal layer, and a light receiving element;
The counter electrode, the pixel electrode, and the liquid crystal layer are disposed on the viewing side with respect to the light receiving element,
The counter electrode is disposed on the viewing side with respect to the pixel electrode and the liquid crystal layer, and transmits visible light.
The pixel electrode is disposed to face the counter electrode, reflects visible light,
The liquid crystal layer is sandwiched between the counter electrode and the pixel electrode, and includes a polymer dispersed liquid crystal material,
A liquid crystal display device comprising a function of imaging infrared rays detected by the light receiving element. In claim 2,
A liquid crystal display device, wherein the pixel electrode is not disposed at a position overlapping with the light receiving element. It has a display function and an imaging function,
A counter electrode, a pixel electrode, a liquid crystal layer, a black layer, and a light receiving element;
The counter electrode, the pixel electrode, and the liquid crystal layer are disposed closer to the viewing side than the black layer and the light receiving element,
The counter electrode is disposed on the viewing side with respect to the pixel electrode and the liquid crystal layer, and transmits visible light.
The pixel electrode is disposed to face the counter electrode, transmits visible light,
The liquid crystal layer is sandwiched between the counter electrode and the pixel electrode, and includes a polymer dispersed liquid crystal material,
The light receiving element has a light receiving sensitivity in an infrared wavelength region,
A liquid crystal display device comprising a function of imaging infrared rays detected by the light receiving element. In claim 4,
The liquid crystal display device, wherein the black layer is disposed at a position overlapping the light receiving element. In any one of Claims 1 thru | or 4,
A liquid crystal display device comprising an infrared transmission filter disposed on a position opposite to the viewing side with respect to the liquid crystal layer and overlapping the light receiving element.