WO2008044370A1

WO2008044370A1 - Liquid crystal display

Info

Publication number: WO2008044370A1
Application number: PCT/JP2007/062307
Authority: WO
Inventors: Hiromi Katoh; Christopher Brown
Original assignee: Sharp Kabushiki Kaisha
Priority date: 2006-10-11
Filing date: 2007-06-19
Publication date: 2008-04-17

Abstract

Disclosed is a liquid crystal display wherein a photodiode is prevented from responding to the illumination light, while suppressing occurrence of dark current in the photodiode. Specifically disclosed is a liquid crystal display comprising a liquid crystal display panel (4) and a backlight. The liquid crystal display panel (4) comprises an active matrix substrate (1), a liquid crystal layer (2) and a counter substrate (3). A plurality of pixels respectively have three sub-pixels (5a-5c), and a color filter provided on the counter substrate (3) has colored layers (6a-6c) respectively corresponding to the sub-pixels. In this liquid crystal display, the backlight is so arranged as to illuminate the liquid display panel (4) from the counter substrate side. The active matrix substrate (1) comprises a photodiode (20) within a display region. The photodiode (20) has such a characteristic that the sensitivity increases as the wavelength of an incident light is shorter, and is so arranged that its light sensing region overlaps a red colored layer (6c) in the thickness direction of the liquid crystal display.

Description

Specification

Liquid crystal display

Technical field

The present invention relates to a liquid crystal display device including a photodiode that reacts to light incident from the observer side of a display screen.

Background art

In recent years, liquid crystal display devices have been widely used as display devices for computers, mobile phones, PDAs, and game machines because of their power saving, thinness, and light weight. In general, a liquid crystal display device includes a liquid crystal display panel and a knock light that illuminates the liquid crystal display panel from the back. A liquid crystal display panel is configured by sandwiching a liquid crystal layer between an active matrix substrate and a counter substrate.

[0003] An active matrix substrate is formed by forming a plurality of pixels in a matrix on a glass substrate. When color display is performed, one pixel is usually composed of three sub-pixels. Each sub-pixel is composed of a TFT and a pixel electrode. Furthermore, the counter substrate includes a counter electrode and a color filter on a glass substrate. The color filter has a red (R), green (G), or blue (B) colored layer for each sub-pixel.

In this liquid crystal display device, the voltage applied between each pixel electrode and the counter electrode is adjusted, and the transmittance of the liquid crystal layer is adjusted for each sub-pixel. As a result, an image is displayed on the display screen by the illumination light of the backlight transmitted through the liquid crystal layer and the colored layer.

As described above, a conventional liquid crystal display device has a function of displaying an image. Recently, however, a liquid crystal display device having a function of capturing an image has been proposed (for example, a patent) Refer to Document 1.) o In the liquid crystal display device disclosed in Patent Document 1, a plurality of photodiodes are formed in a matrix on an active matrix substrate, and the liquid crystal display panel functions as an area sensor.

[0006] Further, in Patent Document 1, a photodiode having a lateral structure is used as each photodiode. Each photodiode uses a TFT process to form a p-type semiconductor region, photodetection region (intrinsic region), and n-type The semiconductor regions are formed in order. However, due to its structure, this photodiode reacts even with illumination light from a knock light that is not only incident on the observer side force.

[0007] Therefore, in Patent Document 1, unlike a general liquid crystal display device, a knock light is arranged on the counter substrate side, and is connected to the n layer of the photodiode in order to block the illumination light. The wiring covers the upper surface of the i layer. In this configuration, since the wiring covering the upper surface of the i layer serves as a light shielding film, the photodiode can be prevented from reacting to the illumination light.

[0008] Further, with this configuration alone, a gap is formed between the wiring covering the upper surface of the i layer and the wiring connected to the p layer (see FIG. 6 of Patent Document 1). Illumination light may be incident on Therefore, in Patent Document 1, a second light shielding film is formed in a layer between the wiring and the photodiode in order to shield the illumination light that attempts to pass through this gap. The second light shielding film is formed by using a TFT gate electrode formation process. Patent Document 1: Japanese Laid-Open Patent Publication No. 2006-3857 (Page 7, Figures 5 and 6)

Disclosure of the invention

Problems to be solved by the invention

Incidentally, in Patent Document 1, the second light-shielding film is formed of a conductive metal material. Further, only a thin insulating layer exists between the silicon film constituting the photodiode and the second light shielding film. For this reason, a depletion layer is less likely to occur in the light detection region. As a result, the liquid crystal display device of Patent Document 1 has a problem that only a low-capacity picked-up image with which dark current is easily generated in a photodiode can be obtained.

An object of the present invention is to provide a liquid crystal display device that can prevent the photodiode from reacting with illumination light while solving the above problems and suppressing the generation of dark current in the photodiode. .

Means for solving the problem

In order to achieve the above object, a liquid crystal display device according to the present invention includes a liquid crystal display panel and a knocklight, and the liquid crystal display panel includes an active matrix substrate in which a plurality of pixels are arranged in a matrix, A liquid crystal layer; and a counter substrate provided with a color filter. Each of the plurality of pixels includes three sub-pixels. A liquid crystal display device having a red, green or blue colored layer for each subpixel, wherein the backlight is arranged to illuminate the liquid crystal display panel from the counter substrate side, and The matrix substrate further includes a plurality of photodiodes in a display area. The photodiode has a characteristic that sensitivity is increased as the wavelength of incident light is shorter, and the light detection area of the photodiode is In the thickness direction of the liquid crystal display device, the liquid crystal display device is disposed so as to overlap the red colored layer. The invention's effect

As described above, in the liquid crystal display device according to the present invention, the red colored layer is interposed between the photodiode and the backlight. Therefore, the force that only the red light out of the light components contained in the illumination light is directed to the photodiode. The photodiode used in the present invention has a short wavelength like red light and low sensitivity to light. It has the characteristic that it is.

Therefore, according to the liquid crystal display device of the present invention, it is possible to suppress the photodiode from reacting with the illumination light. In addition, since it is not necessary to provide a light-shielding film with a conductive metal material, generation of dark current in the photodiode can be suppressed.

Brief Description of Drawings

FIG. 1 is a plan view partially showing a configuration of a liquid crystal display device according to an embodiment of the present invention.

[FIG. 2] FIG. 2 is a cross-sectional view showing a cross-section obtained by cutting along cutting line A-- FIG.

FIG. 3 is a graph showing the spectral sensitivity of the photodiode shown in FIGS. 1 and 2. BEST MODE FOR CARRYING OUT THE INVENTION

[0015] A liquid crystal display device according to the present invention includes a liquid crystal display panel and a backlight, and the liquid crystal display panel includes an active matrix substrate in which a plurality of pixels are arranged in a matrix, a liquid crystal layer, and a color filter. A plurality of pixels each including three sub-pixels, and the color filter includes a red, green or blue colored layer for each of the sub-pixels. The backlight is arranged so as to illuminate the liquid crystal display panel with the counter substrate side force, and the active matrix substrate further includes a plurality of photodiodes in a display region, Photodio The photodiode has a characteristic that the sensitivity increases as the wavelength of incident light is shorter, and the photodiode is arranged so that the photodetection region of the photodiode overlaps the red colored layer in the thickness direction of the liquid crystal display device. It is characterized by being.

In the liquid crystal display device according to the present invention, the photodiode is formed of a silicon film provided on a base substrate of the active matrix substrate, and the silicon film is formed of polycrystalline silicon or continuous grains. A first conductivity type semiconductor region, an intrinsic semiconductor region, and a second conductivity type opposite to the first conductivity type, which are formed of field crystal silicon and provided in order along the surface direction of the silicon film. The semiconductor region may be provided, and the intrinsic semiconductor region may be the light detection region.

In the above aspect, the silicon film is covered with a plurality of insulating films, and is electrically connected to the first conductivity type semiconductor region on the plurality of insulating films. Wiring and a second wiring electrically connected to the second conductivity type semiconductor region are provided, and one of the first wiring and the second wiring is the liquid crystal display device. In the thickness direction, it is preferably formed so as to overlap the intrinsic semiconductor region! In this case, the incidence of illumination light on the photodiode can be further suppressed.

[0018] (Embodiment)

Hereinafter, a liquid crystal display device according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a plan view partially showing a configuration of a liquid crystal display device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a cross section obtained by cutting along the cutting line Α-Α in FIG.

FIG. 1 mainly shows the structure of the pixels formed on the active matrix substrate. For the counter substrate, only the outer shape of the color filter is indicated by a one-dot chain line. Further, the plan view in FIG. 1 shows the state of the active matrix substrate when observing a side force in which pixels are not formed. In FIG. 1, the description of the interlayer insulating film is omitted, and in FIG. 2, hatching of the interlayer insulating film is omitted.

The liquid crystal display device in the present embodiment includes the liquid crystal display panel 4 shown in FIG. 2 and a backlight (not shown) that illuminates the liquid crystal display panel 4. As shown in Fig. 1 and Fig. 2, the liquid crystal surface The display panel 4 includes an active matrix substrate 1, a liquid crystal layer 2, and a counter substrate 3, and is formed by sandwiching the liquid crystal layer 2 between two substrates.

In addition, as shown in FIG. 2, the backlight of the liquid crystal display panel 4 is illuminated from the counter substrate 3 side, and the illumination light 30 is transmitted in the order of the counter substrate 3, the liquid crystal layer 2, and the active matrix substrate 1. To pass through. Although not shown, the liquid crystal display device according to the present embodiment also includes various optical films.

Furthermore, as shown in FIG. 1, the active matrix substrate 1 includes pixels. Although not shown in FIGS. 1 and 2, a plurality of pixels are arranged in a matrix. In the active matrix substrate 1, an area where a plurality of pixels are arranged is a display area. One pixel is composed of three sub-pixels.

[0023] FIG. 1 illustrates only three sub-pixels 5a to 5c. As shown in FIG. 1, each of the sub-pixels 5 a to 5 c includes an active element 7 and a transparent electrode 8. The active element 7 is a thin film transistor (TFT). The transparent electrode 8 is a pixel electrode formed of ITO or the like.

As shown in FIG. 2, the active element 7 includes a silicon film 11 in which a source region 15 and a drain region 16 are formed, and a gate electrode 9. The silicon film 11 is formed of continuous grain boundary crystalline silicon (CGS) because of its excellent charge transfer speed. Both the source region 15 and the drain region 16 are n-type semiconductor regions. A region of the silicon film 11 that overlaps the gate electrode 9 is a channel region 17.

Furthermore, as shown in FIG. 1, the gate electrode 9 is formed integrally with the gate line 10 arranged along the horizontal direction of the screen. A source electrode 12 is connected to the source region 15, and a drain electrode 14 is connected to the drain region 16. The source electrode 12 is formed integrally with a source wiring 13 arranged along the vertical direction of the screen. The drain electrode 14 is connected to the transparent electrode 8.

As shown in FIGS. 1 and 2, the active matrix substrate 1 includes a photodiode 20 in the display area. Although only a single photodiode 20 is shown in FIGS. 1 and 2, in practice, a photodiode 20 is disposed on the active matrix substrate 1 for each pixel. A plurality of photodiodes 20 arranged for each pixel are connected to each other. It functions as a sensor.

As shown in FIG. 2, in the present embodiment, the photodiode 20 is a PIN diode having a lateral structure. The photodiode 20 includes a silicon film provided on a glass substrate 26 that serves as a base substrate of the active matrix substrate 1.

The silicon film constituting the photodiode 20 is formed at the same time using the formation process of the active element 7. For this reason, the photodiode 20 is also formed of continuous grain boundary crystalline silicon (CGS) excellent in charge transfer speed. The silicon film is provided with a p-type semiconductor region (p layer) 21, an intrinsic semiconductor region (transition) 22 and an n-type semiconductor region (n layer) 23 in this order along the plane direction.

In the photodiode 20, the i layer 22 is a light detection region. In the present embodiment, the i layer 22 may be a region that is electrically more neutral than the adjacent p layer 21 and n layer 23. The i layer 22 is preferably a region that does not contain any impurities, or a region where the conduction electron density and hole density are equal to each other.

In FIG. 2, reference numeral 27 denotes an insulating film formed on the glass substrate 26, and the photodiode 20 is formed thereon. The photodiode 20 is covered with interlayer insulating films 28 and 29. 24 indicates the wiring electrically connected to the p-layer 21, and 25 indicates the wiring electrically connected to the n-layer 23.

[0031] Of the two wirings 24 and 25, the wiring 24 connected to the p layer 21 is formed so as to overlap the i layer 22 in the thickness direction of the liquid crystal display device. Specifically, the wiring 24 includes a light shielding portion 24 a at a position overlapping the i layer 22. For this reason, the illumination light 30 is prevented from entering the i layer 23.

[0032] As shown in FIGS. 1 and 2, the counter substrate 3 includes a color filter having a plurality of colored layers. The colored layer is provided for each subpixel. In FIG. 1, only the colored layers 6 a to 6 c corresponding to the sub-pixels 5 a to 5 c among the many colored layers are illustrated.

[0033] Specifically, the colored layers 6a to 6c overlap the transparent electrodes 8 of the corresponding sub-pixels on the surface of the glass substrate 31 serving as the base substrate of the counter substrate 3 in the thickness direction of the liquid crystal display device. Is formed. Further, a black matrix for light shielding is provided between adjacent colored layers. Tas 32 is provided. A transparent counter electrode 33 is formed so as to cover all the colored layers.

Thus, in the liquid crystal display device in the present embodiment, the photodiode 20 is arranged in accordance with the sensitivity characteristic of the force photodiode 20 having the same configuration as that of the conventional liquid crystal display device. This is different from the conventional liquid crystal display device. This point will be described with reference to FIG. FIG. 3 is a graph showing the spectral sensitivity of the photodiode shown in FIGS.

[0035] As described above, the silicon film constituting the photodiode 20 is formed of continuous grain boundary crystalline silicon.

(CGS). Therefore, as shown in FIG. 3, the photodiode 20 formed of continuous grain boundary crystalline silicon has a characteristic that the sensitivity increases as the wavelength of incident light is shorter. That is, the photodiode 20 has a characteristic that it is easy to react to blue light having a short wavelength, has a long wavelength, is difficult to react to red light, and has characteristics.

On the other hand, as shown in FIGS. 1 and 2, the photodiode 20 is disposed so as to overlap the red (R) colored layer 6c in the thickness direction of the semiconductor device. Therefore, only red light out of the light components included in the illumination light is directed toward the photodiode 20. The colored layer 6a is a green (G) colored layer, and the colored layer 6b is a blue (B) colored layer.

For this reason, in the liquid crystal display device according to the present embodiment, illumination light 30 is directed to the i layer 22 from the gap 18 (see FIGS. 1 and 2) between the light shielding portion 24a of the wiring 24 and the wiring 25. Even if light enters, the photodiode 20 hardly reacts. Therefore, according to the present embodiment, in order to shield the illumination light incident through the gap 18, it is not necessary to provide a new light shielding film separately from the light shielding part 24a. Can be suppressed.

Thus, according to the liquid crystal display device of the present embodiment, both the generation of dark current in photodiode 20 and the reaction due to illumination light 30 of photodiode 20 can be suppressed. Further, in the example of FIGS. 1 and 2, the light shielding portion 24a for shielding the i layer 22 from the illumination light 30 is the force provided on the wiring 24 connected to the p layer 21. It is not limited to. The light shielding portion may be provided in the wiring 25 connected to the n layer.

However, depending on which wiring is provided with the light shielding portion, a dark current may be generated in the photodiode 20 or may be supple. In addition, this dark current is The magnitude of the reverse noise voltage applied to the n layer 21 of the photodiode 20 is also related. Therefore, the formation of the light shielding portion in the wiring 24 or the wiring 25 may be performed so that the negative current becomes the smallest depending on the magnitude of the reverse bias voltage.

[0040] In addition, the liquid crystal display device according to the present embodiment may be in any form, provided with the light shielding portion 24a. Even in this embodiment, since the photodiode 20 hardly reacts to the red light, the reaction of the photodiode 20 due to the illumination light 30 is sufficiently suppressed.

In addition, the formation of the silicon film of continuous grain boundary crystalline silicon can be performed, for example, by the following steps. First, an oxide silicon film and an amorphous silicon film are sequentially formed on the interlayer insulating film 27 shown in FIG. Next, a nickel thin film serving as a catalyst for promoting crystallization is formed on the surface of the amorphous silicon film. Next, the nickel thin film and the amorphous silicon film are reacted by annealing to form a crystalline silicon layer at the interface between them. Thereafter, the unreacted nickel film and the silicon-nickel layer are removed by etching or the like. Next, annealing is performed on the remaining silicon film to advance crystallization, so that a silicon film formed of continuous grain boundary crystalline silicon is obtained. Thereafter, the formation of the photoresist and the etching are performed to make the shape of the silicon film a predetermined shape, and further, various types of ion implantation are performed to complete the photodiode 20.

In the present invention, the photodiode 20 is not limited to the one formed by the silicon film of continuous grain boundary crystal silicon. The photodiode 20 only needs to have a characteristic that the sensitivity increases as the wavelength of incident light is shorter. Therefore, the photodiode 20 may be formed of, for example, polycrystalline silicon. This is because polycrystalline silicon has characteristics similar to those of the continuous grain boundary crystalline silicon shown in FIG.

[0043] Formation of a silicon film from polycrystalline silicon can be performed, for example, as follows.

First, an amorphous silicon silicon film is formed. The amorphous silicon film is dehydrogenated, for example, by heating at 500 ° C. for 2 hours, and annealing is performed to crystallize the amorphous silicon film. As a result, a polycrystalline silicon film is obtained. As the annealing method, a known laser annealing method, for example, a method of irradiating an amorphous silicon film with a laser beam with an excimer laser can be mentioned. Industrial applicability

As described above, according to the present invention, the generation of dark current from the photodiode and the photo-diode are provided in the liquid crystal display device including the photodiode that reacts to the light incident from the observer side of the display screen. Reaction due to incidence of illumination light from the diode can be suppressed at the same time. Therefore, the liquid crystal display device according to the present invention can have industrial applicability.

Claims

The scope of the claims

[1] A liquid crystal display panel and a backlight are provided.

The liquid crystal display panel includes an active matrix substrate in which a plurality of pixels are arranged in a matrix, a liquid crystal layer, and a counter substrate provided with a color filter,

Each of the plurality of pixels includes three sub-pixels,

The color filter is a liquid crystal display device provided with a red, green or blue colored layer for each of the sub-pixels,

The backlight is arranged to illuminate the liquid crystal display panel from the counter substrate side,

The active matrix substrate further includes a plurality of photodiodes in a display area,

The photodiode has a characteristic that the sensitivity increases as the wavelength of incident light is shorter, and the photodetection region of the photodiode overlaps the red colored layer in the thickness direction of the liquid crystal display device. Arranged! A liquid crystal display device characterized by squeezing.

[2] The photodiode is formed of a silicon film provided on a base substrate of the active matrix substrate,

The silicon film is formed of polycrystalline silicon or continuous grain boundary crystal silicon, and is provided in order along a surface direction of the silicon film, a first conductivity type semiconductor region, an intrinsic semiconductor region, and the first 2. The liquid crystal display device according to claim 1, further comprising a semiconductor region of a second conductivity type opposite to the conductivity type, wherein the intrinsic semiconductor region becomes the photodetection region.

[3] The silicon film is covered with a plurality of insulating films,

A first wiring electrically connected to the first conductivity type semiconductor region and a second wiring electrically connected to the second conductivity type semiconductor region on the plurality of layers of insulating films And are provided,

3. The liquid crystal according to claim 2, wherein any one of the first wiring and the second wiring is formed so as to overlap the intrinsic semiconductor region in the thickness direction of the liquid crystal display device. Display device.