JP3281991B2 - Liquid crystal display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device having a light detecting function such as an observer's line of sight detecting system.

[0002]

2. Description of the Related Art A conventional active matrix type liquid crystal display device using a thin film transistor (TFT) includes, for example, forming a thin film semiconductor layer made of Si or the like on a transparent substrate and forming a TFT as a switching element on the thin film semiconductor layer. Is configured. A transparent electrode such as ITO is formed thereon to form a liquid crystal drive electrode. The input side of the TFT is connected to a signal wiring, and the output side is connected to a liquid crystal drive electrode. T
By synchronizing the gate signal input to the gate wiring for controlling the FT with the video signal input to the signal wiring, a video signal can be sent to each pixel electrode to display an image.

When an electronic viewfinder is formed by a liquid crystal display device, it is difficult to attach an input pad to each gate wiring and signal wiring one by one and connect it to a driving circuit because of its small size. Therefore, the liquid crystal drive circuit and the liquid crystal display section are generally formed on the same substrate.

[0004] A technique has been proposed in which a liquid crystal display device as described above is provided with a light detection function and is used as information input means. For example, by providing an electronic viewfinder of a video camera with a line-of-sight detection device using a photodetector, a function of performing autofocus in a direction in which the line of sight is directed can be provided. The line-of-sight detection means can be realized by irradiating the user's eyeball with light and detecting a reflected Purkinje image from the eyeball with a photodetector. When a photodetector and a drive circuit for the photodetector are configured on the same substrate as the liquid crystal display device, a liquid crystal display device having a line-of-sight detection function can be manufactured compactly and inexpensively, and the output from the line-of-sight detection device can be further reduced. Feedback can be provided to the liquid crystal display device.

[0005]

The object of the invention is to be Solved However, the following problem there was Tsu and if an attempt is made to form a liquid crystal display device and the line-of-sight detection device with the on-chip.

A thin film semiconductor layer used for a display portion and a drive circuit portion of a liquid crystal display device is single crystal or polycrystal, and is not suitable for a photoelectric conversion region. This is because most of the light passes through the thin film semiconductor layer, so that the detection efficiency becomes very small. Taking single-crystal Si as an example, the quantum efficiency is 5% when the wavelength of the detection light is 800 nm and the Si film thickness is 0.5 μm. Therefore, when a quantum efficiency of 80% or more is required, the Si film thickness needs to be 16 μm or more.

[0007]

The present invention improves the detection efficiency of a photodetector by forming the photoelectric conversion portion of the photodetector of a liquid crystal display device with an amorphous Si (hereinafter α-Si) compound. It is intended.

That is, the present invention provides a liquid crystal display,
Circuit for driving the liquid crystal display, and the subject to be observed the liquid crystal display unit
Illuminating means for illuminating the eyeball, receiving reflected light from the eyeball
Photodetector provided with a photoelectric conversion unit, and a driving circuit for the photodetector.
, The liquid crystal display unit, its driving circuit, and the photodetector
And its driving circuit are formed on the same substrate, and the photodetector
Photoelectric conversion part is composed of amorphous Si compound
A liquid crystal display device characterized in that:

[0009]

FIG. 1 shows a first embodiment of the present invention.
This embodiment is an example in which the present invention is applied to a liquid crystal display device having a visual line detection function. Substrate 101 constituting the display device in FIG, 102 is a liquid crystal display unit, the driving circuit 103 is a liquid crystal display unit which is configured on the substrate 101, 104 is an optical detector for detecting the line of sight, 105 photodetector 104 is a drive circuit. Reference numerals 102 to 105 are formed on the same substrate 101.

FIG. 2 illustrates the operation of the display device according to the present embodiment. A light source 1 is provided on the back of a substrate 101 constituting a liquid crystal display device.
An image is displayed by arranging the pixel 06 and controlling the light transmittance of the pixels arranged in the liquid crystal display unit 102 by a signal from the driving circuit 103. Line of sight of people have Prying the liquid crystal display unit is detected by the following method.

Light detection for detecting a line of sight is performed on the substrate 101.
The device 104 and its driving circuit 105 are configured. The light from the light source 107 for line-of-sight detection is converted into parallel light by a lens 108 and applied to the eyeball 109 of the subject. The light source 107 contains light having a wavelength used for line-of-sight detection. For example, infrared light is practical. Eyeball 109
Reflection Purkinje image from are imaged on the <br/> 104 exits light detection by the lens 110. The output from the optical detector 104 and processed in an external signal processing circuit, of the subject eye 1
The line of sight of 09 can be obtained. Alternatively, the light detector 1
It is also possible to configure the signal processing circuit 04 on the substrate 101.

FIG. 3 shows a method of manufacturing this liquid crystal display device. A thin film semiconductor layer 302 made of single crystal Si or poly Si is formed on a transparent substrate 301. Next, the thin film semiconductor layer 30
2 are separated by etching or oxidation to form an active layer 303. The gate oxidation film 304 is deposited after the formation of the gate electrode 305 on the active layer 303, to form a transistor 306. After forming an insulating layer 307 thereon, the signal wiring 30
8. A gate wiring 309 is formed and connected to the source and gate of the transistor 306, respectively. Transistor 30
6 is a drain electrode 3 made of direct or metal.
11 is connected to the pixel electrode 310. By sandwiching the liquid crystal between the substrate manufactured as described above and the opposing substrate, a voltage can be applied to the liquid crystal in accordance with the drain output voltage of the transistor 306.

[0013] shows the configuration of the liquid crystal display device and configured on-chip <br/> photodetector in FIG. Reference numeral 301 denotes a substrate for forming a liquid crystal display device. A metal wiring 402 made of Al or the like is formed on a substrate. Further, n-type α-Si 403 is deposited on the metal wiring 402 by a CVD method, and α-SiGe 404 is formed thereon by a plasma CVD method. In this embodiment, the metal wiring 402 is tightened so as to cover the entire region where α-SiGe 404 is deposited.

The plasma CVD method of α-SiGe will be described. The wafer is placed on the electrodes and heated to 250 ° C.
Then, while flowing a mixed gas of SiH ₄ , GeH ₄ , and H ₂ , an AC voltage of 13.56 MHz is applied between the electrode on which the wafer is mounted and the electrode facing the wafer, thereby forming α-SiGe on the wafer. Can be deposited.
At this time, by adjusting the flow rates of SiH ₄ and GeH ₄ , Si
And Ge can be changed, and the band gap of α-SiGe can be controlled. In this embodiment, the band cap of α-SiGe is 1.45 e.
Ideally, it is set to about V.

Α-SiGe 40 deposited in this manner
4, p-type α-Si 405 is deposited by a CVD method, and then n-type α-Si 403 and α-Si
Ge404 and p-type α-Si405 are patterned. Further, by forming the insulating film 406 by, for example, PSG and then forming the transparent electrode 407, the structure in FIG. 4 can be obtained. ITO is generally used as a material for the transparent electrode.

In this structure, incident light passes through the transparent electrode 407 and enters the depleted α-SiGe region 404. α-SiGe has an absorption coefficient of about 1 compared to single crystal Si.
When the film thickness of α-SiGe is 1 μm, which is about an order of magnitude larger, a quantum efficiency of 80% can be obtained for infrared light having a wavelength of 800 nm. In this embodiment, the metal wiring 402 is confined on the entire surface of the light detection area, and the light transmitted through the light detection area is reflected by the metal wiring 402 and is incident again on the light detection area. Can be increased. On the other hand, even if external light incident from the back surface of the substrate is transmitted through the transparent substrate 401, the metal wiring 4
02 prevents light from entering the detection area.

In addition to the metal wiring 402, the substrate 3
Needless to say, it is possible to provide reflection by providing a reflection film on the back surface of 01.

With the above configuration, since the absorbed detection light excites electrons and holes, the amount of incident light can be extracted as an electric signal by applying a bias between the metal wiring 402 and the transparent electrode 407. By arranging a filter that transmits desired infrared light on the front surface of the detector, it goes without saying that the influence of light other than infrared light reflected by the eyeball can be reduced.

In this embodiment, α-SiGe is used for 404, but the effect of the present invention can be obtained by using α-SiSn. Further, the α-Si layer 403 is an n-type,
It is also possible to make the Si layer 404 p-type.

[0020] The switching transistor provided in the optical detector constructed as described above, the Purkinje images is measured by reading the sequentially output by the light detector of the driving circuit 105 shown in the first, the line of sight of the subject You can ask.

(Example 2) A photodetector for detecting light from the back surface of the substrate was formed by the same process as in Example 1. FIG. 5 is a diagram illustrating the operation of this embodiment.
Shown in

The operation mechanism and manufacturing method of this embodiment are basically the same as those of the first embodiment, but the structure of the photodetector 104 is different from that of the first embodiment as shown in FIG. In this embodiment, the metal wiring 402 is in contact with a part of the light detection area.
Further, a metal electrode 408 of Al or the like is formed instead of the transparent electrode 407 of the first embodiment.

In this embodiment, the metal electrode 408 covers the entire surface of the photodetection area, and the light transmitted through the photodetection area is reflected by the metal electrode 408 and reenters the photodetection area. Detection efficiency can be increased. On the other hand, external light incident from the surface of the substrate is
08 prevents light from entering the detection area.

[0024] The switching transistor provided in the optical detector constructed as described above, the Purkinje images is measured by reading the sequentially output by the light detector of the driving circuit 105 shown in FIG. 1, the line of sight of the subject You can ask.

[0025] (Example 3) can be an optical detector according to the present invention is disposed in the liquid crystal display unit. Thus, a point on the display device can be selected and used as input means using a normal light source or laser light spotted by the lens as a pointer. An example is shown in FIG. The symbol is FIG.
It is the same as, 1 01 is a substrate for supporting the liquid crystal display unit 102. The driving circuit 103 drives the liquid crystal display unit 102 and the photodetector 104. In the present embodiment, a plurality of photodetectors 104 are studded in the liquid crystal display unit.

FIGS. 8A to 8C are sectional views showing the manufacturing method of this configuration.
It is shown in (c). The basic steps and methods are the same as in FIG. Active layer 303 consisting of alpha-Si or poly-Si on the transparent substrate 301, a gate oxide film 304 thereon, depositing a gate conductive <br/> electrode 305, after forming the pixel transistors, selectively a metal film The drain electrode 311 of the pixel transistor and the metal wiring 402 of the photodetector are formed. After forming an insulating film 307 thereon, a signal wiring 308 and a gate wiring 309 are formed, and a source and a pixel transistor of the pixel transistor are respectively formed.
Connect to gate. Drain electrode 3 of pixel transistor
11 is connected to the pixel electrode 310. Further, an n-type α-Si 403 is formed on the wiring 402 of the photodetector by α-SiGe 40.
4 is formed in the same manner as in the first embodiment.

Further, a p-type α-S is formed on α-SiGe405.
After depositing i, a photodetector is formed by forming a transparent electrode 407. ITO is generally used as a material for the transparent electrode. After depositing an insulating layer 406 thereon, a transparent electrode is formed to form a pixel electrode 310. Also, the pixel electrode 31
It is also possible to configure the 0 and the transparent electrode 407 of the photodetector by the same process. With this manufacturing method, the configuration shown in FIG. 8C can be realized. In this embodiment, as in the first embodiment, the metal wiring 402 is tightly formed on the entire surface of the light detection area, and the light transmitted through the light detection area is reflected by the metal wiring 402 and reenters the light detection area. Therefore, the detection efficiency can be further increased. On the other hand, even if external light incident from the back surface of the substrate has passed through the transparent substrate 301, it is blocked by the metal wiring 402,
It is possible to prevent the light from entering the detection area.

By sandwiching the liquid crystal between the substrate formed as described above and the opposing substrate, a voltage can be applied to the liquid crystal according to the drain output voltage of the transistor.

Further, the photodetector can be arranged in the liquid crystal display section, and the output from the photodetector is sequentially detected by using a switching transistor formed simultaneously with the pixel transistor, so that the liquid crystal display is controlled by a pointer using light. It is possible to detect which part of the unit is pointed. It is needless to say that an erroneous operation due to external light can be prevented by attaching an optical filter to the front surface of the detector so that light having a wavelength that passes through the filter is included in the light of the pointer.

[0030]

As described above, according to the effects of the present invention, a photodetection mechanism having high quantum efficiency can be formed on-chip even on a thin film semiconductor substrate. This makes it possible to inexpensively constitute an electronic view finder comprising a line-of-sight detection knowledge instrumentation <br/> location on-chip by. Further, a photodetector can be provided in the liquid crystal display portion, and a display device which can perform input by indicating an arbitrary position on the display portion by using a light pointer can be configured.

[Brief description of the drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is an operation explanatory diagram of the first embodiment of the present invention.

FIG. 3 is a view showing a manufacturing process of the first embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a configuration of a photodetector according to the present invention.

FIG. 5 is an operation explanatory diagram of the second embodiment of the present invention.

FIG. 6 is a sectional view illustrating a configuration of a photodetector according to a second embodiment of the present invention.

FIG. 7 is a diagram showing a third embodiment of the present invention.

FIG. 8 is a view showing a manufacturing process according to a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 101 Substrate 102 Liquid crystal display part 103 Drive circuit 104 Photodetector 105 Drive circuit 106 Back light source 107 Line of sight detection light 108 Lens 109 Eyeball 110 Lens 301 Transparent substrate 302 Thin film semiconductor layer 303 Active layer 304 Gate oxide film 305 Gate electrode 306 Transistor 307 Insulating film 308 Signal wiring 309 Gate wiring 310 Pixel electrode 311 Drain electrode 402 Metal wiring 403 n-type α-Si 404 α-SiGe 405 p-type α-Si 406 Insulating film 407 Transparent electrode 408 Metal electrode

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-2-191915 (JP, A) JP-A-3-249622 (JP, A) JP-A-4-46472 (JP, A) JP-A-6-1994 205342 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G02F 1/1333 G02F 1/13 505 G09G 3/36 G02F 1/1345

Claims (6)

(57) [Claims] 1. A liquid crystal display unit, a driving circuit for driving the liquid crystal display unit, and illumination of an eyeball of a subject to observe the liquid crystal display unit
Illuminating means, photoelectric conversion for receiving light reflected from the eyeball
Light detector with parts, a drive circuit, the photodetector, the liquid crystal display unit and a driving circuit, said optical detector and drive its
Dynamic circuit is formed on the same substrate, a liquid crystal display device characterized by photoelectric conversion of the optical detector is constituted by an amorphous Si compound. 2. The liquid crystal display device according to claim 1 , wherein the photodetector is disposed in the liquid crystal display unit. 3. The light corresponding to the photoelectric conversion unit on the substrate.
In the detection region, the liquid crystal display device according to claim 1 or 2, characterized in that the reflective film reflecting light from the eyeball to reflect light on the back surface of the side to be incident is formed. 4. The method according to claim 1, wherein the amorphous Si compound is amorph.
4. SiGe according to claim 1, wherein
A liquid crystal display device according to any of the above. 5. The semiconductor device according to claim 1, wherein said photoelectric conversion portion is an n-type amorphous S
i, amorphous SiGe and p-type amorphous Si
The method according to claim 1, wherein:
Liquid crystal display device. 6. The infrared detector according to claim 1, wherein said photodetector has an infrared transmitting filter on its front surface.
A filter is arranged.
The liquid crystal display device according to any one of the above.