JPH06289422A - Substrate for reflection type liquid crystal display device - Google Patents

Abstract

PURPOSE:To facilitate miniaturization and to enable bright and high-resolution display by covering the active matrix substrate with a light shieldable insulating film over the entire surface on the transistors(TRs) and pixel electrodes. CONSTITUTION:The field effect type TRs 58 and the pixel electrodes 40 connected to drain electrodes 37 of the TRs 58 are formed on the substrate 35 consisting of single crystal silicon and a light shielding layer 41 of an alloy film composed of silicon and germanium, etc., is closely formed over the entire surface covering the pixel electrodes 40, the TRs 58, etc. Further, a dielectric mirror layer 42 consisting of the insulating film is formed over the entire surface on this light shielding layer 41 and a liquid crystal oriented film 43 is formed thereon. Both of the light shielding layer 41 and the dielectric mirror layer 42 have an insulating characteristic and, therefore, if liquid crystals 47 are clamped between this active matrix substrate 57 and a counter substrate 46 formed with the oriented film 44 and electrodes 45 on the surface, the voltages applied on the pixel electrodes 40 are divided in equivalent capacity of the respective insulating layers and are applied on the liquid crystal layer 47 as well.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate of a projection type display device using an active matrix liquid crystal display panel capable of brightly displaying a high definition image on a large screen.

[0002]

2. Description of the Related Art Conventionally, as a projection type display device using a liquid crystal display device, as shown in FIG. 2, a transmission type liquid crystal display panel 1 which modulates transmitted light and projects it on a screen 3 by a projection lens 2 is shown. The transmission light of the projection display device and the transmission type active matrix liquid crystal display panel 4 is modulated as shown in FIG. There is known a reflection type projection display device in which the light incident through the polarization beam splitter 7 is modulated and reflected by the device 6 and the output light of the polarization beam splitter 7 is projected onto the screen 9 by the projection lens 8.

FIG. 4 shows a sectional structure of the transmission type projection liquid crystal display device of FIG. A thin film transistor including a source, drains 11 and 12, a gate insulating film 13, and a gate electrode 14 is formed on the transparent insulating substrate 10, and a liquid crystal driving transparent electrode 15 is connected to the drain electrode 12 and the liquid crystal 1
Apply voltage to 6. Protective film 1 on the thin film transistor
7. A liquid crystal alignment film 18 is formed. The liquid crystal 16 is sandwiched between the substrate 10 on which the thin film transistor is formed and the glass substrate 19 on which the transparent electrode 20 and the alignment film 21 are formed.

FIG. 5 shows a sectional structure of an optical spatial modulator used in the reflection type projection liquid crystal display device of FIG. One substrate 2
A transparent electrode 23, a semiconductor film 24 made of amorphous silicon or the like having photoconductivity, a light-shielding film 25, a dielectric mirror layer 26, and a liquid crystal alignment film 70 are provided on the second substrate 2, and the other substrate is a glass substrate 27. A transparent electrode 28 and a liquid crystal alignment film 29 are formed on the above. A liquid crystal 30 is sandwiched between the substrates 22 and 27. When there is incident light on the photoconductive layer 24, the resistance is lowered and the voltage of the transparent electrode is applied to the liquid crystal layer 30 via the light shielding film 25 and the dielectric mirror 26. In the liquid crystal layer, the applied light changes the modulation state of incident light, so that an image on amorphous silicon can be formed on the liquid crystal layer 30 to modulate light.

[0005]

The transmissive projection liquid crystal display device of FIG. 2 is capable of displaying with a single liquid crystal panel and is small in size and capable of high-definition display. However, it is generally an active liquid crystal display panel such as a transistor. Since the element is highly sensitive to light, deterioration of image quality is unavoidable in a display device such as a projection display device used in the presence of strong incident light. On the other hand, in the reflection type projection liquid crystal display device of FIG. 3, the spatial light modulator can realize high image quality even in the presence of strong incident light. However, in this case, two liquid crystal panels, that is, a panel for inputting an image and a panel for reflecting and displaying the input image are required, and considering that an optical imaging system between the panel and the spatial light modulator is required. It is difficult to downsize the device.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to obtain a substrate of a reflection type active matrix display device which can be easily miniaturized and which can perform bright and high resolution display in order to solve the conventional problems.

[0007]

In order to solve the above problems, the present invention forms an opaque insulating film on the transistors and pixel drive electrodes of an active matrix liquid crystal panel to enable a bright, compact and high-definition display. did.

[0008]

In the substrate of the liquid crystal display device configured as described above, incident light can be absorbed by the light-shielding insulating film so that the light does not affect the transistor. Since it is a reflection type display, a mirror can be formed over the transistor, and the existence of the transistor does not cause a loss of the effective area of the pixel, so that the light utilization efficiency is improved. Furthermore, if an insulating light-shielding film is formed, the transmittance for incident light can be reduced to 0.1% or less, the light-shielding property is perfect, and the transistor does not malfunction even under strong incident light (for example, 1 million lux). be able to.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a reflective projection liquid crystal display device according to an embodiment of the present invention. Polarized light is incident on the reflective liquid crystal display device 31 via a polarizing beam splitter 32, and the incident light is displayed on the display device 31. Image modulated. The reflected light passes through the polarization beam splitter and then is projected onto the screen 34 via the projection lens 33.

FIG. 6 is a sectional structural view of the reflection type liquid crystal display device shown in FIG. 1, in which a source 36, a source 36,
A field effect transistor including a drain 37, a gate insulating film 38, and a gate electrode 39, and a pixel electrode 40 connected to the drain electrode 37 of the transistor are formed.
A light shielding layer 41 is formed over the entire surface of the pixel electrode 40, the transistor, etc. without any gap. A suitable material for forming the light-shielding layer 41 is a mixture of silicon and germanium. On the light-shielding layer 41, a mirror made of an insulating film is formed over the entire surface, a dielectric mirror layer 42, and the liquid crystal alignment film 4 is formed on the mirror.
3 is formed. This substrate, the alignment film 44 and the electrode 4
If the liquid crystal 47 is sandwiched between the counter substrates 46 having the surface 5 formed thereon, the signal applied to the pixel electrode 40 applies a voltage to the liquid crystal layer via the insulating light shielding layer 41 and the dielectric mirror layer 42. You can The light shielding layer 41 prevents incident light from affecting the semiconductor film of the transistor. Light-shielding layer 4
Since both 1 and the dielectric mirror 42 are insulating, the voltage of the pixel electrode 40 is divided by the equivalent capacitance of each insulating layer, and the voltage is also applied to the liquid crystal layer 47. The dielectric mirror 42 usually has a structure in which two layers having different refractive indexes are repeatedly formed in multiple layers. At this time, it is desirable that the dielectric constant of each layer is as large as possible, because there is no voltage loss due to the mirror layer. As the light-shielding layer 41, a multilayer film in which two layers of silicon and silicon oxide are repeatedly formed,
It is used because an alloy film of silicon and germanium has an insulating property and a light shielding property.

FIG. 7 is a cross-sectional structural view showing another embodiment of the present invention, which is a field effect transistor comprising a source 49, a drain 50, a gate insulating film 51 and a gate electrode 52 on a single crystal silicon substrate 48. Drain electrode 5 of transistor
A pixel electrode 53 connected to 0 is formed. The insulating film 54 covers the transistor. Pixel electrode 53,
A light-shielding layer 55 is formed over the entire surface of the transistor and the like without any gap. On the light-shielding layer 55, a reflective electrode 56 having a planar overlap with the pixel electrode 53 is formed separately for each pixel. An alignment film 57 is formed on the reflective electrode 56.
Are formed. The substrate 48, the alignment film 58, and the electrode 5
If the liquid crystal 61 is sandwiched between the counter substrates 60 on which 9 are formed, a signal applied to the pixel can apply a voltage from the pixel electrode 53 to the liquid crystal layer 61 via the reflective electrode 56 by capacitive coupling. .

A 45 ° twist type is used as the liquid crystal layer. It is oriented so as to differ by 45 degrees in a direction parallel to the surface of the substrate facing the semiconductor substrate. When no voltage is applied to the liquid crystal, the light incident through the polarizing plate is reflected and again passes through the polarizing plate to come out. When a voltage is applied to the liquid crystal, the liquid crystal molecules are aligned vertically, and the liquid crystal layer exhibits birefringence with respect to the obliquely incident polarized light.Therefore, by adjusting the thickness of the liquid crystal material and the liquid crystal layer to an appropriate value, The light can be rotated by 90 degrees and emitted. This light is absorbed by the polarizing plate. In this way, it is possible to display a reflection mode in which the transmission and absorption of light is controlled by turning the voltage on and off.

As a liquid crystal material, a liquid crystal material such as a polymer dispersion liquid crystal or a dynamic scattering liquid crystal (DSM) whose light scattering state can be changed by applying a voltage is also used in the display using the above birefringence. You can do the same. In this case, since it is not necessary to use a polarizing plate, light is not absorbed and a bright display can be realized. Since the reflective electrode is separated for each pixel, crosstalk with adjacent pixels does not occur. The reflective electrode blocks the incident light and enhances the light blocking effect.

If a single crystal semiconductor is used as the substrate, especially if single crystal silicon is used, an integrated circuit can be formed thereon, so that various functions can be realized. Typical of these are circuits for driving pixels, such as shift registers, sample hold circuits, amplifiers, etc., control circuits for drive circuits, inspection circuits for confirming circuit operation, and brightness of incident light. There are photodetectors that detect pod signals, temperature detectors, and so on. Since the driving circuit drives the liquid crystal layer through the light-shielding layer, the dielectric mirror, or the like, it is preferable that the driving circuit be formed using a transistor that can operate at high voltage, for example, a transistor having an LDD structure.

As a material for reflecting light, if a dielectric mirror formed by stacking dielectric thin films in multiple layers is used, a reflective layer can be formed of an insulator, so pattern formation of the mirror is not necessary, but the mirror is formed of metal. In that case, a metallic mirror is divided and formed for each pixel in order to hold a specific potential for each pixel.

[0016]

As described above, according to the present invention, the insulating light-shielding film is formed on the transistor and the pixel electrode, so that a small display device in which the driving circuit is formed on the same substrate can be realized. There is an effect that it is possible to realize a bright display with a high resolution and a compact reflective type with one panel.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a structure of a reflective liquid crystal display panel that is an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a transmissive projection display device according to a conventional method.

FIG. 3 is an explanatory diagram of a reflective projection display device according to a conventional method.

FIG. 4 is an explanatory diagram showing a cross-sectional structure of a reflective display panel according to a conventional method.

FIG. 5 is an explanatory view showing a sectional structure of a reflective display panel according to a conventional method.

FIG. 6 is an explanatory diagram showing a cross-sectional structure of a reflective liquid crystal display panel that is an embodiment of the present invention.

FIG. 7 is an explanatory diagram showing a cross-sectional structure of a reflective liquid crystal display panel that is another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transmissive liquid crystal display panel 4 Transmissive active matrix liquid crystal display panel 6 Spatial modulator 11 Source 12 Drain 14 Gate electrode 17 Liquid crystal drive electrode 24 Semiconductor film 25 Light-shielding film 26 Dielectric mirror film 30 Liquid crystal 41 Light-shielding layer 42 Dielectric mirror layer 53 liquid crystal drive electrode 55 light-shielding layer 56 reflective electrode

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hiroaki Takasu 6-31-1, Kameido, Koto-ku, Tokyo Seiko Electronics Co., Ltd.

Claims (3)

[Claims] 1. In an active matrix substrate used as a substrate of an active matrix type liquid crystal display device in which a switching transistor is formed for each pixel, a transistor and a pixel electrode are entirely covered with a light shielding insulating film. Substrate of the characteristic liquid crystal display device. 2. The substrate of the reflective liquid crystal display device according to claim 1, wherein the light-shielding insulating film is covered with a dielectric mirror. 3. The substrate of the reflective liquid crystal display device according to claim 1, wherein a metal reflective electrode separated for each pixel is formed on the light-shielding insulating film.