JP2000193994A - Reflection type liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reflection type liquid crystal display device which can yield excellent contrast by decreasing the reflectance of an anti reflection film below 10% over the entire visible light region. SOLUTION: On a substrate 1, at least transistors 2, an insulating layer 4, a shading film 13a formed of metal formed so as to cover the transistors 2 in the insulating layer 4, the reflection preventive film 14, pixel electrodes 15 arrayed having a prescribed pixel pitch, a liquid crystal layer 16, and a glass substrate 17 covering the entire surface of the liquid crystal layer 16 are stacked in order and a wiring layer 12 is provided to connect the transistors 2 and pixel electrodes 15, thus constituting the reflection type liquid crystal device. In this case, the reflection preventive film 14 is composed of nitride 14a and a dielectric film 14 with a different refractive index from the insulating layer 4 which are formed in order on the shading film 13a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device in which a reading light is made incident and a display is performed by reflecting the reading light.

[0002]

2. Description of the Related Art A liquid crystal projector using a transmission type or reflection type liquid crystal display device has been conventionally known. In a transmissive liquid crystal display device, a driving circuit and wiring for driving the liquid crystal are formed in the plane of the liquid crystal panel and formed with a width of about 10 μm around a pixel, so that light modulation over the entire display area of the liquid crystal panel is performed. (Hereinafter referred to as an aperture ratio). At present, even a transmissive liquid crystal display device having the highest aperture ratio has a report of an aperture ratio of only about 60%. In a transmissive liquid crystal display device, as the number of pixels increases (high resolution) and the pixel density increases, the aperture ratio decreases. Therefore, it is difficult to obtain a high-luminance display image with a liquid crystal projector equipped with the transmissive liquid crystal display device. Met. Therefore, in recent years, a liquid crystal projector using a reflective liquid crystal display device has been developed and put into practical use as a high-brightness, high-resolution liquid crystal projector.

[0003] A reflective liquid crystal display device is generally formed of a plurality of pixel electrodes formed in a matrix at a predetermined pitch on a substrate, and formed between the substrate and the pixel electrodes. It has a configuration including a driving circuit for driving and a liquid crystal layer formed on the pixel electrode. The operation of the reflection type liquid crystal display device is such that the drive circuit writes image information to the liquid crystal layer, irradiates read light from the liquid crystal layer side, and modulates information light corresponding to the image information. It is done by radiating

Usually, an ineffective area irrespective of light modulation of the reflection type liquid crystal display device has a distance between the pixel electrodes of 0.5.
In the case of a reflective liquid crystal display device having a pixel electrode pitch of, for example, 14 μm,
An aperture ratio of up to 93% can be obtained. Therefore, the reflection type liquid crystal display device has been attracting attention as a liquid crystal display device suitable for providing a high-brightness, high-resolution liquid crystal projector.

[0005] Such a reflection type liquid crystal display device will be described with reference to FIGS. 5 and 6. FIG. 5 is a sectional view showing a liquid crystal panel of a conventional reflection type liquid crystal display device. FIG. 6 is a plan view showing a state in which a conventional reflective liquid crystal display device is viewed from above. As shown in FIGS. 5 and 6, the liquid crystal panel of the conventional reflection type liquid crystal display device includes a silicon substrate 1, a MOS transistor 2 and a storage capacitor 3 formed in parallel on the silicon substrate 1, and The pixel A is composed of an interlayer insulating film 4 having a refractive index of 1.45 and a liquid crystal cell 5 sequentially formed on the MOS transistor 2 and the storage capacitor 3. An isolation oxide film 9 is formed between the MOS transistor 2 and the storage capacitor 3,
The type transistor 2 and the storage capacitor 3 are electrically separated. The MOS transistor 2 includes a source 6, a drain 8, and a gate 7 held between the source 6 and the drain 8.

The storage capacitor 3 is composed of a high-concentration layer 10 formed in the silicon substrate 1 and a storage electrode 11 disposed opposite the high-concentration layer 10 with an interlayer insulating film 4 interposed therebetween. The liquid crystal cell 5 includes a pixel electrode 15 made of Al having a pixel electrode gap 15a, a liquid crystal layer 16, and a glass substrate 17 sequentially laminated. As will be described later, in the interlayer insulating film 4, the readout light that enters from the pixel electrode gap 15a
A light shielding film 13a made of Al and having a predetermined pitch is formed between the MOS type transistor 2 and the pixel electrode gap 15a and the pixel electrode 15 so as not to enter the type transistor 2.

The wiring layer 13b is connected to the pixel electrode 15, the drain 8 of the MOS transistor 2, and the holding electrode 11 via the wiring layer 12. Further, on the light shielding film 13a and the wiring layer 13b, an antireflection film 1 made of titanium nitride is formed.
4 are formed. The source 6 of the MOS transistor 2 is connected to an image signal wiring (not shown), and the gate 7 is connected to
It is connected to a scanning signal wiring (not shown).

Next, the operation of the liquid crystal panel of the conventional reflection type liquid crystal display device will be described. When a scanning signal is applied to the gate 7 via a scanning signal line (not shown) in a state where the image signal is applied to the source 6 via an image signal line (not shown), the MOS transistor 2 is turned on and charges of the image signal are discharged. The storage capacitor 3 and the liquid crystal cell 5 are charged, and this image signal is written to the liquid crystal layer 16. In this state, when reading light is incident on the liquid crystal cell 3 from the glass substrate 17 side, the reading light undergoes light modulation in the liquid crystal layer 16 while passing through the liquid crystal cell 3 in accordance with an image signal, and the antireflection film 14 is formed. Then, the light is reflected by the pixel electrode 15, light-modulated again by the liquid crystal layer 16, and emitted from the glass substrate 17 as image information light. An image can be displayed by enlarging and projecting the image information light emitted from the glass substrate 17 onto a screen.

[0009]

However, the conventional reflection type liquid crystal display device has the following problems. In the case of the single-panel system using one liquid crystal panel, light in the entire visible light region (wavelength of 4000 to 7000 angstroms) is used, but it is used for the oxide film used for the interlayer insulating film 4 and the antireflection film 14. Titanium nitride only has a low reflectance with respect to light of a part of the wavelength, but cannot prevent reflection of light of other wavelengths. Therefore, the pixel electrode gap 15a
Is reflected by the antireflection film 14 and penetrates into the liquid crystal layer 17 of an adjacent pixel, causing interference with the read light applied to the adjacent pixel, thereby lowering the contrast. Was. For this reason, a high-quality display image having good contrast could not be obtained. Typically,
The reflectance of the antireflection film 14 is 10% in the entire visible light region.
In the following case, it is said that the read light is prevented from being reflected by the antireflection film 14 and entering the liquid crystal layer 16 of the adjacent pixel, so that the contrast is not significantly deteriorated. It is required that the reflectance be 10% or less. In the case of a three-panel system using three liquid crystal panels, the antireflection films 14 used for the red, blue, and green liquid crystal panels, respectively, only need to prevent reflection of incident light. That is, in the antireflection film 14 of the liquid crystal panel used for red, if only red (light having a wavelength of 6000 Å to 7000 Å) is prevented from being reflected, an image with good contrast can be obtained. , The reflectance is 1
It is not necessary to keep it below 0%. However, it is necessary to optimize the red, blue, and green liquid crystal panels by changing the thickness of the antireflection film 14, and the red, blue, and green liquid crystal panels cannot be shared. Was. For this reason, the productivity has been reduced. If the antireflection effect of the antireflection film 14 on the light shielding film 13a is low, the pixel electrode gap 15a
The read light incident from the surface is reflected by the antireflection film 14 and the pixel electrode 15.
And reaches the MOS transistor 2 to deteriorate the transistor performance of the MOS transistor 2.

Accordingly, the present invention has been made in view of the above problems, and has a reflection type liquid crystal display in which the reflectance of an antireflection film is reduced to 10% or less over the entire visible light region and a good contrast is obtained. It is intended to provide a device.

[0011]

According to the present invention, there is provided a reflection type liquid crystal display device comprising at least a transistor on a substrate, an insulating layer, and a light-shielding metal formed in the insulating layer so as to cover the transistor. A film, an anti-reflection film, a pixel electrode arranged with a predetermined pixel pitch, and a liquid crystal layer,
In a reflective liquid crystal display device in which a glass substrate covering the entire surface of the liquid crystal layer is sequentially laminated, and a wiring layer connecting the transistor and the pixel electrode, the antireflection film is sequentially formed on the light shielding film. And a dielectric film having a different refractive index from the insulating layer.

According to a second aspect of the present invention, in the reflective liquid crystal display device according to the first aspect, the antireflection film is a film having a reflectance of 10% or less with respect to light having a wavelength of 4000 to 7000 angstroms. It is characterized by.

According to a third aspect of the present invention, in the reflective liquid crystal display device according to the first or second aspect, the nitride is titanium nitride, and the dielectric film is silicon nitride.

According to a fourth aspect of the present invention, in the reflective liquid crystal display device according to any one of the first to fourth aspects, the light shielding film is made of Al;
The thickness of the titanium nitride is 800 angstrom to 1
200 Å, the thickness of the silicon nitride is 5
Characterized as 00 angstrom

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a reflection type liquid crystal display device of the present invention will be described with reference to FIGS. In the reflection type liquid crystal display device of the present invention, the antireflection film 14 is formed of titanium nitride (hereinafter, referred to as T) instead of the pixel A of the conventional reflection type liquid crystal display device.
The pixel M has two layers, i.e., iN) 14a and silicon nitride (hereinafter, SiN) 14b. FIG. 1 is a diagram showing one pixel of a liquid crystal panel of a reflection type liquid crystal display device of the present invention. FIG. 2 is a diagram showing the relationship between the reflectance and the wavelength when the thickness of silicon nitride and titanium nitride formed sequentially on Al is fixed. FIG.
FIG. 4 is a diagram illustrating a relationship between the reflectance and the wavelength when the thickness of titanium nitride is fixed and the thickness of silicon nitride is changed among silicon nitride and titanium nitride sequentially formed on Al.
FIG. 4 is a view showing the relationship between the reflectance and the wavelength when the thickness of silicon nitride is fixed and the thickness of titanium nitride is changed among the silicon nitride and titanium nitride sequentially formed on Al. . The same components as those in the related art are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 1, the liquid crystal panel of the reflection type liquid crystal display device of the present invention comprises a silicon substrate 1, a MOS transistor 2 and a storage capacitor 3 formed in parallel on the silicon substrate 1, Pixels M each including an interlayer insulating film 4 sequentially formed on the MOS transistor 2 and the storage capacitor 3 and a liquid crystal cell 5 are arranged. MO
An isolation oxide film 9 is formed between the S-type transistor 2 and the storage capacitor 3, and the MOS transistor 2 and the storage capacitor 3
Are electrically separated from each other. The MOS transistor 2
It comprises a source 6, a drain 8, and a gate 7 sandwiched between the source 6 and the drain 8.

The storage capacitor 3 includes a high-concentration layer 10 formed in the silicon substrate 1 and the high-concentration layer 10 and the interlayer insulating film 4.
And the holding electrode 11 arranged to face the other. As described later, the pixel electrode gap 15a is provided in the interlayer insulating film 4.
A light-shielding film 13a made of Al having a predetermined pitch is provided between the MOS-type transistor 2 and the pixel electrode gap 15 so that readout light entering from the MOS-type transistor 2 does not enter the MOS-type transistor 2.
a and the pixel electrode 15. The liquid crystal cell 5 includes a pixel electrode 15 made of Al having a pixel electrode gap 15 a, a liquid crystal layer 16 sequentially formed on the pixel electrode 15, and a glass substrate 17.

Further, the wiring layer 13b is connected to the pixel electrode 15 and the drain 8 of the MOS transistor 2 via the wiring layer 12.
And the holding electrode 11. An antireflection film 14 is formed on the light shielding film 13a and the wiring layer 13b. This antireflection film 14 is made of SiN1 on TiN14a.
4b. At this time, the thickness of the TiN 14a is 800 Å to 1200 Å, and the thickness of the SiN 14b is 500 Å. Since SiN 14b is an insulator, TiN
It is formed not only on the N14a but also in the interlayer insulating film 4 so as to prevent the readout light entering from the pixel electrode gap 15a from propagating between the pixel electrode 15 and the TiN 14a and reaching the MOS transistor 2. Have been. The refractive index of the SiN 14b is 2.00, which is different from that of the interlayer insulating film 4. Source 6 of MOS transistor 2
Is connected to an image signal wiring (not shown), and the gate 7 is connected to a scanning signal wiring (not shown).

Next, the operation of the reflection type liquid crystal display device of the present invention will be described. Via an image signal wiring not shown,
When a scanning signal is applied to the gate 7 via a scanning signal wiring (not shown) in a state where the image signal is applied to the source 6, M
The OS-type transistor 2 is turned on, the charge of the image signal is charged to the storage capacitor 3 and the liquid crystal cell 5, and the image signal is written to the liquid crystal layer 16. In this state, when reading light is incident on the liquid crystal cell 3 from the glass substrate 17 side, the reading light undergoes light modulation in the liquid crystal layer 16 while passing through the liquid crystal cell 3 in accordance with an image signal, and the antireflection film 14 is formed. And pixel electrode 15
The light is again modulated by the liquid crystal layer 16 and emitted from the glass substrate 17 as image information light. An image can be displayed by enlarging and projecting the image information light emitted from the glass substrate 17 onto a screen.

Here, the pixel M of the reflection type liquid crystal display device of the present invention is irradiated with visible light, and TiN 14a and S
The relationship between the reflectance of the antireflection film 14 having a structure in which iN14b and iN14b were sequentially formed and the wavelength in the visible light region was examined. The results will be described with reference to FIGS. The reflectance of the antireflection film 14 is such that visible light having a wavelength of 4000 to 7000 angstroms is used as readout light, and this readout light is incident from the glass substrate 17 side.
It is obtained by measuring the ratio of the reflected light of the read light to the read light. Here, the reflectance is 100
Shown in%. In the measurement of the reflectance of the antireflection film 14, the thickness of the TiN 14a and the thickness of the SiN 14b were changed. First, the relationship between the reflectance and the wavelength in the visible light region when TiN having a thickness of 800 angstroms and SiN having a thickness of 500 angstroms are sequentially formed on Al will be described with reference to FIG.

In FIG. 2, the reflectivity of TiN and Al formed on Al is shown for comparison, and * indicates TiN (800 angstrom thick) formed sequentially on Al.
And SiN (thickness 500 Å) (hereinafter referred to as S
iN (500A) / TiN (800A) / Al)
△ represents TiN (thickness 800) formed on Al
Angstrom) (hereinafter TiN (800A) / Al
■ is Al. TiN (800
A) / Al and the reflectance of Al and Al are 10% or more, whereas SiN (500 A) / TiN (800 A) / A
The reflectance of 1 is between 4000 Angstroms and 70 wavelengths.
10% or less over the area of 00 Angstroms. From this, it can be seen that if a structure in which TiN having a thickness of 800 angstroms and SiN having a thickness of 500 angstroms are sequentially formed on Al is used, a reflectance of 10% or less can be obtained in a wavelength region of 4,000 angstroms to 7000 angstroms.

Next, the relationship between the reflectance and the wavelength in the visible light region when TiN having a thickness of 800 angstroms and SiN having a changed thickness are sequentially formed on Al will be described with reference to FIG. I do. In FIG. 3, * indicates that the thickness of SiN is 200 Å (hereinafter, referred to as SiN 200), ２００ indicates that the thickness of SiN is 500 Å (hereinafter, referred to as SiN 500), and ■ indicates the thickness of SiN.
The thickness of N is 800 Å (hereinafter referred to as SiN80).
0). SiN 200 has a reflectance of 10% or less in a wavelength range of 4000 to 6500 Å, but exhibits a reflectance of 10% or more in a range of 6500 Å to 7000 Å, and SiN 800 has a reflectance of 10% in a wavelength range of 4000 to 7000 Å. The above reflectivity is shown.

On the other hand, as described above, the reflectivity of SiN 500 is 10% or less over a wavelength range of 4000 Å to 7000 Å. From this, it can be seen that if a structure in which TiN having a thickness of 800 angstroms and SiN having a thickness of 500 angstroms are sequentially formed on Al is used, a reflectance of 10% or less can be obtained in a wavelength region of 4,000 angstroms to 7000 angstroms.

Further, TiN having a varied thickness on Al
The relationship between the reflectance and the wavelength in the visible light region when SiN having a thickness of 500 Å is sequentially formed will be described with reference to FIG. In FIG. 4, * indicates that the thickness of TiN is 400 angstroms (hereinafter, referred to as TiN400), △ indicates that the thickness of TiN is 800 angstroms (hereinafter, referred to as TiN800), and ■ indicates the TN.
iN has a thickness of 1200 Å (hereinafter referred to as TiN
1200). TiN400 has a wavelength of 400
In the range of 0 Å to 5900 Å, the reflectance is 10% or less, while in the range of 5900 Å to 7000 Å, the reflectance is 10% or more. On the other hand, TiN80
The reflectance of 0 and TiN1200 shows a reflectance of 10% or less over a wavelength range of 4000 Å to 7000 Å. From this, A
800 to 1200 Å thick TiN and 500 Å thick S
With a structure in which iN is sequentially formed, 10% in the wavelength range of 4,000 Å to 7000 Å
It can be seen that the following reflectance is obtained.

As described above, the anti-reflection film 14 has a structure in which Al is used for the light-shielding film 13a and TiN having a thickness of 800 Å to 1200 Å and SiN having a thickness of 500 Å are sequentially formed on the light-shielding film 13. Is used, the wavelength is 4000 angstrom to 7
The reflectance of the read light can be suppressed to 10% or less over the entire visible light region of 2,000 angstroms. For this reason, it is possible to prevent the reflected light of the read light from entering the adjacent pixels, and it is possible to improve the contrast.
As a result, in a single-panel liquid crystal display device using only one liquid crystal panel, a display image having good contrast can be obtained.

In a three-panel type liquid crystal display device using three liquid crystal panels, the reflectance of the read light can be suppressed to 10% or less over the entire visible light region having a wavelength of 4000 to 7000 angstroms. The three liquid crystal panels corresponding to the primary color light can be shared, and the productivity is improved. Further, it is possible to prevent the read light incident from the pixel electrode gap 15a from reaching the MOS transistor 2 and deteriorating the transistor performance.

[0027]

According to the reflection type liquid crystal display device of the present invention,
Since the anti-reflection film is composed of a nitride sequentially formed on the light-shielding film and a dielectric film having a different refractive index from the insulating layer, light entering from between pixel electrodes is reflected and reaches the transistor. Deterioration of transistor performance can be prevented. Al is used for the light-shielding film, and a thickness of 800
Angstroms to 1200 Angstroms Ti
Since N and SiN having a thickness of 500 Å are sequentially used for the anti-reflection film, the reflectance of the read light is suppressed to 10% or less over the entire visible light range of wavelengths from 4,000 Å to 7000 Å. be able to. For this reason, it is possible to prevent the reflected light of the read light from entering the adjacent pixels, thereby improving the contrast. As a result, in the single-panel system using only one liquid crystal panel, a display image having good contrast can be obtained. In a three-panel system using three liquid crystal panels, a wavelength of 4,000 Å to 70 Å is used.
Since the reflectance of the reading light can be suppressed to 10% or less over the entire visible light region of 00 angstroms, 3
The three pixels corresponding to the primary color light can be shared, and the productivity is improved.

[Brief description of the drawings]

FIG. 1 shows a liquid crystal panel of a reflection type liquid crystal display device of the present invention.
FIG. 3 is a diagram illustrating pixels.

FIG. 2 is a diagram showing the relationship between the reflectance and the wavelength when the thickness of silicon nitride and titanium nitride sequentially formed on Al is fixed.

FIG. 3 is a diagram showing the relationship between the reflectance and the wavelength when the thickness of titanium nitride is fixed and the thickness of silicon nitride is changed among silicon nitride and titanium nitride sequentially formed on Al. .

FIG. 4 is a diagram showing the relationship between the reflectance and the wavelength when the thickness of silicon nitride is fixed and the thickness of titanium nitride is changed among silicon nitride and titanium nitride sequentially formed on Al. .

FIG. 5 is a sectional view showing one pixel of a liquid crystal panel of a conventional reflection type liquid crystal display device.

FIG. 6 is a plan view showing a state in which a conventional reflective liquid crystal display device is viewed from above.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate (substrate), 2 ... MOS transistor, 3 ... Capacitance, 4 ... Interlayer insulating film (insulating layer), 5 ... Liquid crystal cell, 6 ... Source, 7 ... Gate, 8 ... Drain, 9 ...
Isolation oxide film, 10 high concentration layer, 11 holding electrode, 12
Wiring layers, 13a, 13b: light shielding film, 14: antireflection film,
14a: titanium nitride (nitride), 14b: silicon nitride (dielectric film), 15: pixel electrode, 15a: gap between pixel electrodes, 16: liquid crystal layer, 17: glass substrate

Claims (4)

[Claims] At least a transistor, an insulating layer, a light-shielding film made of a metal formed in the insulating layer so as to cover the transistor, and an anti-reflection film are provided on the substrate.
Pixel electrodes arranged with a predetermined pixel pitch, a liquid crystal layer, and a glass substrate covering the entire surface of the liquid crystal layer are sequentially laminated,
In the reflection type liquid crystal display device including the transistor and a wiring layer connecting the pixel electrode, the antireflection film has a different refractive index from the nitride sequentially formed on the light shielding film and the insulating layer. A reflective liquid crystal display device comprising a dielectric film. 2. The anti-reflection coating according to claim 1, wherein said anti-reflection film has a wavelength of 4,000 Å to 7000 Å.
2. The reflective liquid crystal display device according to claim 1, wherein the film has a reflectance of 0% or less. 3. The reflection type liquid crystal display device according to claim 1, wherein said nitride is titanium nitride, and said dielectric film is silicon nitride. 4. The light-shielding film according to claim 1, wherein said light-shielding film is made of Al, and said titanium nitride has a thickness of 800 to 1200 angstroms, and said silicon nitride has a thickness of 500 angstroms. Reflective liquid crystal display.