JPH11109390A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a liquid crystal display device high in aperture ratio and improved in picture quality by providing a reflector having a random ruggedness on a surface opposed to a substrate, first electrode oppositely arranged on the random rugged surface between the substrate and the reflector, and a second electrode placed opposite to the first in the manner of covering it through an insulating film. SOLUTION: A storage capacity auxiliary electrode 8 is electrically connected to a pixel electrode 10 in a contact hole provided in an inter-layer insulating film 11, with an auxiliary capacity formed between it and the auxiliary capacity line 5. In other words, the ruggedness of the pixel electrode 10 is formed by that of the inter-layer insulating film 11; each recessed part of the pixel electrode 10 positioned on the auxiliary capacity line 5 is brought into contact with the storage capacity auxiliary electrode 8, by means of the contact hole provided in this inter-layer insulating film 11, with the auxiliary electrode 8 electrically connected to the pixel electrode 10. The flat part on the TFT area of this inter-layer insulating film 11 is also formed with a light shielding film 12 made of a black resin. In addition, a columnar spacer 13 is arranged on the light shielding film 12 in the TFT area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reflection type liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices having great advantages such as thin and light weight and low power consumption have been developed for personal computers such as Japanese word processors and notebook personal computers.
It is actively used as a display device of the A-device and a video display device such as a television.

In particular, a reflection type liquid crystal display device does not have illumination light by itself and can display by external light, so that power consumption can be reduced. Therefore, a portable type computer or an electronic device driven by a battery can be used. Demand for displays such as notebooks is increasing.

For example, JP-A-6-273800 describes a reflection type liquid crystal display device in which a reflection plate is provided inside a liquid crystal panel.

[0005] This reflection type liquid crystal display device is formed with a liquid crystal layer interposed between a pair of opposing translucent substrates. One of the pair of translucent substrates is an array substrate on which pixel electrodes and switching elements are formed. This pixel electrode is also a reflector, has irregularities, and reflects incident light from the other substrate side. The arrangement of the pixel electrodes is on the liquid crystal layer side surface,
In addition, it is formed on an insulating film formed in a region including the switching element portion. In addition, the pixel electrodes are spaced apart from each other between adjacent pixel electrodes so as to maintain a mutually electrically insulated state,
In addition, a channel is formed between the switching element portion and the pixel electrode to form a region that is not conductive. further,
A light-shielding film is formed in a predetermined region on the insulating film with a gap between the pixel electrode and the pixel electrode in a range for maintaining an electrical insulation state therebetween. Since this light-shielding film also serves as a reflector, it has a shape with irregularities. In this reflection type liquid crystal display device, there is no parallax because the light shielding film also serves as the reflection plate, and the display area can be increased because of the pixel-placed structure. Further, light incident on the switching element is shielded by the light shielding film, so that light leakage of the switching element does not occur.

However, in this method, the light-shielding film (metal) is in an electrically floating state, and the characteristics of the TFT element tend to be unstable. Also, since the insulating film interposed between the device and the device is also uneven, the insulating film is partially thinned. Easy to deteriorate. In addition, since the light-shielding film and the pixel electrode are in the same layer, a sufficient interval must be provided so that there is no electrical conduction, which is disadvantageous in terms of aperture ratio.

[0007] In addition, conventionally, there are methods of extending the pixel electrode to cover the switching element or providing a light-shielding film on the opposing substrate to prevent light leakage of the switching element. And there is a problem that the aperture ratio is disadvantageous.

As described above, in the conventional reflection type liquid crystal display device, the reflection plate is formed on the switching element so that there is no electrical conduction with the pixel electrode, or the pixel electrode is extended to cover the element. Alternatively, a configuration is adopted in which a light-shielding film is provided on the opposite substrate. However, the light-shielding film of the conventional reflective liquid crystal display device has an effect on the image quality,
It was not satisfactory.

[0009]

In a reflection type liquid crystal display device, in order to obtain good reflection characteristics, the concave and convex shape of the reflector is essential, and the concave and convex shape must be random.
However, if the pixel electrode has a random uneven shape that also serves as a reflector, there is a problem that a storage capacitance value formed between the pixel electrode and the storage capacitance line varies for each pixel.
This problem becomes more serious in a high-definition liquid crystal display device in which one pixel is small.

SUMMARY OF THE INVENTION The present invention has been made in order to address the above-mentioned problems of the prior art, and there is provided a reflection type liquid crystal display device which can reduce the capacitance fluctuation due to the uneven shape of the pixel electrode even in high definition. The purpose is to provide.

It is another object of the present invention to provide a liquid crystal display device having a high aperture ratio and good image quality by solving the problems of the spacer and the light-shielding film in the conventional reflection type.

[0012]

According to a first aspect of the present invention, there is provided a liquid crystal display device comprising: a substrate having at least a surface having an insulating property; and a random arrangement formed on the substrate in a matrix and facing the substrate. A reflective electrode having irregularities, means for selectively applying a display signal to the reflective electrode, a first electrode disposed between the substrate and the reflective electrode to face the random irregular surface, Between the first electrode and the random uneven surface of the reflective electrode, is electrically connected to the reflective electrode, and is opposed to the second electrode via the insulating film so as to cover the first electrode.
And the electrode of (1).

According to the first aspect of the present invention, an electrode (second electrode) opposed to the auxiliary capacitance line (first electrode) is arranged between the random uneven surface of the reflective electrode and the auxiliary capacitance line, In addition, since it is electrically connected to the reflection electrode, a capacitance is formed between this electrode and the auxiliary capacitance line. Accordingly, the second region is formed over the entire area where the auxiliary capacitance line and the reflective electrode overlap.
Since the auxiliary capacitance is determined by the overlapping area of the auxiliary capacitance line and the second electrode, the pixel capacitance does not fluctuate even if the unevenness of the reflective electrode is formed at random. The auxiliary capacitance can be formed with high precision without variation in the auxiliary capacitance between the pixels to which the display signal is applied by the display signal applying means constituted by the scanning lines, the signal lines and the switching elements.

Further, according to a second aspect of the present invention, the first substrate comprises:
In a liquid crystal display device including a light-transmitting second substrate opposed to the first substrate and a liquid crystal layer provided in a gap between the substrates, one surface of the first substrate on a liquid crystal layer side is provided. A reflective electrode arranged in a matrix and having random irregularities on a surface facing the substrate, an element for supplying a signal charge to each of the reflective electrodes corresponding to the reflective electrode, and a first substrate and a reflective electrode A first electrode disposed between the first electrode and the random uneven surface of the reflective electrode, and electrically connected to the reflective electrode,
A second electrode opposed to the first electrode with an insulating film interposed therebetween; an insulating light-shielding film formed on the element; a first substrate and a second substrate disposed on the insulating light-shielding film; And a columnar spacer for holding a gap between the substrates.

According to the second aspect of the present invention, similarly to the first aspect of the present invention, by disposing a second electrode between the auxiliary capacitance line (first electrode) and the reflection electrode, this electrode and the auxiliary electrode are connected to each other. A storage capacitor is formed between the storage capacitor line and the storage capacitor, and even if unevenness of the reflective electrode is formed at random, the storage capacitor can be formed with high precision without variation in the storage capacitor between pixels. Also,
Since the organic insulating light-shielding film is arranged on the switching element part, the pixel electrode can be arranged so that the edge part overlaps the switching element part, and the pixel electrode is enlarged to fill the effective area. And the aperture ratio is improved. Further, since the columnar spacer is provided on the flat light-shielding film on the switching element, the cell gap control is easy.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 are a schematic sectional view and a schematic plan view, respectively, showing one embodiment of the liquid crystal display device of the present invention.

In this reflection type liquid crystal display device, as shown in FIG. 1, a liquid crystal layer 3 is held between an array substrate 1 and a counter substrate 2.

As shown in FIG. 2, the array substrate 1 includes a scanning line 4 made of Mo-W and a storage capacitor line 5 made of the same material as the scanning line 4 and substantially parallel to each other. , And a signal line 6 substantially orthogonal to the scanning line 4.

In the array substrate 1, as shown in FIG. 1, a gate insulating film 7 is formed on the scanning lines 4 and the auxiliary capacitance lines 5.
First, a first gate insulating film made of a silicon oxide film and a second gate insulating film made of a silicon nitride film deposited thereon are formed. Each scanning line 4 includes a connection end drawn out to one end side of the glass substrate.

Further, on the gate insulating film 7, a signal line 6 made of Al or an Al alloy such as an Al--Y alloy or Ag and a storage capacitance auxiliary electrode 8 are formed. However, the signal line 6 and the storage capacitance auxiliary electrode 8 are insulated.
Each signal line 6 includes a connection end extended to the other end side of the glass substrate. The storage capacitance auxiliary electrode 8 is formed of the gate insulating film 7
Are arranged on the auxiliary capacitance line 5 via the.

A TFT is provided at the intersection of the scanning line 4 and the signal line 6.
A pixel electrode 10 to which a display signal is applied via a TFT 9 is disposed on an interlayer insulating film 11 disposed on the scanning line 4 and the signal line 6. Although the interlayer insulating film 11 has irregularities, the TFT region is flattened. The material can be formed of an organic insulating film such as polyimide, but by forming a laminated structure of an organic insulating film and an inorganic insulating film such as silicon nitride,
Interlayer insulation is further improved.

The connection end of the signal line 6 is connected to a signal line connection pad formed simultaneously with the pixel electrode 10, and the connection end of the scanning line 4 is connected to the pixel electrode 10 through a contact hole formed in the gate insulating film 7. At the same time, they are connected to the formed scanning line connection pads.

The storage capacitor auxiliary electrode 8 is formed on the interlayer insulating film 1.
The storage capacitor 1 is electrically connected to the pixel electrode 10 through a contact hole, and forms a storage capacitor with the storage capacitor line 5.

That is, the unevenness of the pixel electrode 10 is formed by the unevenness of the interlayer insulating film 11, and the respective recesses of the pixel electrode 10 located on the auxiliary capacitance line 5 are formed by the contact holes formed in the interlayer insulating film 11. The storage capacitor auxiliary electrode 8 is electrically connected to the pixel electrode 10.

Therefore, by providing the storage capacitance auxiliary electrode 8 so as to substantially cover the area where the storage capacitance line 5 and the pixel electrode 10 overlap, the storage capacitance value of each pixel is reduced by the concave portion of the pixel electrode 10 on the storage capacitance line 5. Since it is determined by the overlapping area of the storage capacitance auxiliary electrode 8 and the auxiliary capacitance line 5 irrespective of the number, an almost constant auxiliary capacitance can always be formed,
Variations in the auxiliary capacitance between pixels can be eliminated.

A light-shielding film 12 made of black resin is further formed on a flat portion of the interlayer insulating film 11 on the TFT region. Further, a columnar spacer 13 is arranged on the light shielding film 12 in the TFT region. The columnar spacers 13 may be arranged in all the pixels, or pixels with and without the columnar spacers may be distributed at a specific density.

As described above, the flat light shielding film 1 on the TFT 9
By providing the columnar spacer 13 on 2, the cell gap control becomes easy.

When the columnar spacer 13 is formed on the counter substrate side, the bottom surface is smaller than the light-shielding film 12 by the cell alignment accuracy, and the height is set to a thickness necessary for the cell gap. When the columnar spacers 13 are formed on the array substrate 1 side, they may be formed integrally with the light shielding film 12 or may be formed separately.

The material of the columnar spacer 13 may be any material as long as it is insulating. For example, the light shielding film 12
The columnar spacer 13 can be made of the same black resin as described above or a layer obtained by superimposing a colored layer of a color filter.

When the columnar spacer 13 on which the color layer of the color filter is laminated is provided on the counter substrate 2 side, a structure in which the common electrode 14 covers the surface of the columnar spacer 13 may be employed.

The columnar spacers 13 need only be formed at a predetermined density in the display area of the screen, and need not be provided for all pixels. When columnar spacers made of black resin are provided for all pixels, TFTs for strong light such as direct sunlight
This is effective in preventing image quality deterioration due to light leakage.

On the other hand, the opposing substrate 2 opposing the array substrate 1 is configured by disposing a common electrode 14 made of a transparent electrode material such as ITO on a glass substrate.

Further, a detailed configuration of the array substrate 1 according to the present embodiment and its operation will be described. The pixel electrode 10 is arranged on the scanning line 4 via the gate insulating film 7 and the interlayer insulating film 11, and also on the signal line 6 via the interlayer insulating film 11. Therefore, since the pixel electrode 10 is not in the same layer as the signal line 6 or the scanning line 4, even if the pixel electrode 10 is arranged sufficiently close to the signal line 6 or the scanning line 4, the pixel electrode 10 overlaps the signal line 6 or the scanning line 4. However, short-circuit failure does not occur. In this embodiment mode, the pixel electrode 10 is partially overlapped with each wiring as shown in FIG.

By adopting such a pixel-placed structure, a high production yield and a high definition and high aperture ratio can be designed.

Moreover, in the present embodiment, the contour of the signal line 6 matches the contour of the low-resistance semiconductor film and the semiconductor film. More specifically, a low-resistance semiconductor film and a semiconductor film in addition to the gate insulating film 7 are always laminated at the intersection of the signal line 6 and the scanning line 4. For this reason, even if a mask shift occurs during each patterning, the step generated in the signal line 6 is sufficiently reduced, and there is no variation in capacitance between the signal line 6 and the scanning line 4. Variations in scanning line capacity or signal line capacity are also reduced. Further, static electricity at intersections between the signal lines 6 and the scanning lines 4, dust during the process, or interlayer short-circuits due to pinholes in the respective insulating films can be suppressed, thereby securing a high product yield. The same applies between the signal line 6 and the auxiliary capacitance line 5.

In the present embodiment, the signal line 6 and the source electrode / drain electrode of the TFT 9 and the pixel electrode 10 are formed of the same Al-Y alloy, so that electrical connection can be achieved with low contact resistance. .

Next, the array substrate manufacturing process will be described in detail with reference to FIGS. FIG.
(E), FIG. 4 and FIG. 5 are sectional views showing respective manufacturing steps in the order of the manufacturing process of the array substrate.

First, as shown in FIG. 3A, a Mo-W alloy film is deposited to a thickness of 300 nm on a glass substrate 101 by sputtering, and is exposed using a first mask pattern, followed by development and patterning. Through the glass substrate 10
The scanning line 4 and the auxiliary capacitance line 5 including the connection end 102 drawn out to one end side of 1 are manufactured.

Thereafter, as shown in FIG.
A first method comprising a silicon oxide film having a thickness of 150 nm
After depositing the gate insulating film 103, the second gate insulating films 104, 5 made of a silicon nitride film having a thickness of 150 nm are further formed.
A semiconductor film 105 of a-Si: H having a thickness of 0 nm and a channel protective film 106 of a silicon nitride film having a thickness of 200 nm are formed by a CVD method without being continuously exposed to the atmosphere.

Further, the channel protective film 1 is self-aligned with the scanning line 4 by a backside exposure technique using the scanning line 4 as a mask.
06 is patterned, further exposed using a second mask pattern so as to correspond to the TFT region, developed, and patterned (second patterning), as shown in FIG. Next, an island-shaped channel protective film 106 is formed.

Thereafter, at the stage of FIG. 3D, the exposed surface of the semiconductor film 105 is treated with hydrofluoric acid so that a good ohmic contact is obtained, and a 30 nm-thick n-type film containing phosphorus as an impurity is formed by the CVD method. ^A low-resistance semiconductor film 107 made of ⁺ a-Si: H is deposited, and an Al-Y alloy film is further deposited to a thickness of 200 nm.

Next, exposure and development are performed using a third mask pattern, and the Al—Y alloy film, the low-resistance semiconductor film 107 and the semiconductor film 105 are converted into a second gate insulating film 104 and a channel protective film made of a silicon nitride film. By controlling the etching selectivity with respect to 106, the RIE (Re
The semiconductor film 105 and the low-resistance semiconductor film 1 are patterned by an active ion etching (third patterning) method.
07, a source electrode 108, a signal line 6, a connection end integral with the signal line 6, a drain electrode 109 integral with the signal line 6, and a storage capacitance auxiliary electrode 8.

Next, a process for forming the interlayer insulating film 11 will be described. For example, a polyimide film (Nissan Chemical: RN-812, Nippon Synthetic Rubber: HRC series, etc.) is formed on the entire surface of the array substrate on which the TFT 9 is formed. And a plurality of circular projections are formed by random patterning by photolithography using a fourth mask pattern, and further heat-treated, as shown in FIG. , With a rounded convex shape.

At this time, the TFT portion of the interlayer insulating film 11 has a flat shape without any irregularities, and the interlayer insulating film 11 is formed on the connection end 102 of the signal line 6 and the scanning line 4. Don't do it.

Further, a second interlayer insulating film made of a silicon nitride film having a thickness of 200 nm is deposited thereon, exposed and developed using a fifth mask pattern, and the interlayer insulating film 11 corresponding to the source electrode 108 is removed. Then, a contact hole is formed, and the gate insulating films 103 and 104 corresponding to the connection end 102 of the signal line 6 are removed to form a contact hole. At the same time, the first and second gate insulating films 103 and 104 corresponding to the connection ends 102 of the scanning lines 4 are removed to form contact holes. Further, a contact hole for connection between the storage capacitor auxiliary electrode 8 and the pixel electrode 10 is formed.

Next, a metal thin film made of an Al-Y alloy is formed on the entire surface of the second interlayer insulating film having the irregularities, and is exposed, developed, and patterned using a sixth mask pattern to form a pixel. The electrode 10 is manufactured.

At the same time, a scanning line connection pad made of the same material as the pixel electrode 10 and electrically connected to the connection end 102 of the scanning line 4 via the contact hole is manufactured. Also, the connection end 1 of the signal line 6 via the contact hole
A signal line connection pad made of the same material as the pixel electrode, which is electrically connected to the pixel electrode 02, is manufactured.

Next, a black resin is formed and patterned to form a columnar spacer 13 also serving as a light shielding film 12 as shown in FIG.

As described above, in the above manufacturing process, the basic structure of the array substrate 1 of this embodiment can be manufactured with a smaller number of masks than before.

That is, the pixel electrode 10 is arranged on the uppermost layer, and the signal line 6, the source electrode 108, the drain electrode 109, and the semiconductor film 105 are collectively patterned based on the same mask pattern. The step of producing a contact hole for exposing the connection end 102 of the signal line 6 and the scanning line 4 is simultaneously performed with the production of the contact hole for connection between the source electrode 108 and the pixel electrode 10, thereby reducing the step generated in the wiring. This is an optimal process that simultaneously achieves mutually different requirements of preventing a reduction in manufacturing yield and improving productivity with a small number of masks.

In this embodiment, the semiconductor film 105 is a
Although the description has been given of the case where the semiconductor device is made of -Si: H, it is needless to say that a polysilicon film or the like may be used.
Further, the drive circuit portion may be integrally formed in the peripheral region.

Further, when the pixel electrode 10 is partially overlapped on the signal line 6 or the scanning line 4, it is shielded with a metal film or the like via an insulating layer at least between the pixel electrode 10 and the signal line 6. If the electrodes are arranged, the pixel electrode 10
Can reduce the influence of the potential from the signal line 6.

On the other hand, a common electrode 14 made of a transparent conductive material such as ITO is formed on the counter substrate 2 to a thickness of 0.1 μm, and an alignment film is further formed thereon. In this embodiment, since the light-shielding film 12 is formed on the TFT 9 of the array substrate 1, it is not necessary to form the light-shielding film in the region of the counter substrate 2 facing the TFT 9.

The array substrate 1 and the opposing substrate 2 are bonded to face each other, and the liquid crystal 3 is injected between them to complete the reflection type liquid crystal display device. At this time, the gap between the array substrate 1 and the opposing substrate 2 is held by the columnar spacer 13 formed on the light shielding film 12.

As the liquid crystal 3, for example, a guest-host liquid crystal mixed with a black dye (trade name: ZLI2, manufactured by Merck Ltd.)
327) to an optically active substance (manufactured by Merck, trade name S81)
Use a mixture of 1).

The liquid crystal used in the present invention is not limited to the guest-host liquid crystal, but may be a polymer dispersion or a birefringence mode, and may be provided with an internal polarizing plate on the pixel electrode.

In this embodiment, a monochrome reflection type liquid crystal display device is manufactured. However, a color may be provided by providing a coloring layer on a counter substrate or a pixel electrode. Further, the liquid crystal display mode may be changed to a birefringent mode to achieve colorization.

[0058]

According to the present invention, it is possible to provide a reflection type liquid crystal display device which can reduce the capacitance fluctuation due to the random unevenness of the reflection electrode, that is, the pixel electrode even at the time of high definition, and has a high aperture ratio and good image quality. can do.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a liquid crystal display device of the present invention.

FIG. 2 is a plan view of the liquid crystal display device shown in FIG.

FIG. 3 is a cross-sectional view illustrating an example of a manufacturing process of the liquid crystal display device according to the present invention.

FIG. 4 is a sectional view illustrating a manufacturing process example of the liquid crystal display device according to the present invention, following FIG. 3;

FIG. 5 is a cross-sectional view illustrating a manufacturing process example of the liquid crystal display device according to the present invention, following FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Array substrate 2 ... Opposite substrate 3 ... Liquid crystal layer 4 ... Scanning line 5 ... Storage capacitance line 6 ... Signal line 8 ... Storage capacitance auxiliary electrode 9 ... TFT 10 pixel electrode (reflective electrode) 11 interlayer insulating film 12 light-shielding film 13 columnar spacer 14 common electrode

Claims (2)

[Claims] 1. A substrate having at least a surface exhibiting an insulating property; a reflective electrode disposed on the substrate in a matrix and having random irregularities on a surface facing the substrate; Means for applying a display signal; a first electrode disposed between the substrate and the reflective electrode so as to face the random uneven surface; and a first electrode and a random uneven surface of the reflective electrode. A second electrode, which is electrically connected to the reflective electrode and is disposed to face the first electrode with an insulating film interposed therebetween so as to cover the first electrode;
A liquid crystal display device comprising: 2. A liquid crystal display device comprising: a first substrate; a light-transmitting second substrate opposed to the first substrate; and a liquid crystal layer provided in a gap between the substrates. A reflective electrode disposed in a matrix on one surface of the first substrate facing the liquid crystal layer and having random irregularities on a surface facing the substrate; and supplying a signal charge to each of the reflective electrodes corresponding to the reflective electrode An element, a first electrode opposed to the random uneven surface between the first substrate and the reflective electrode, and a first uneven electrode having a random uneven surface between the first electrode and the reflective electrode. A second electrode electrically connected to the reflective electrode and opposed to the first electrode via an insulating film; an insulating light-shielding film formed on the element; Maintaining a gap between the first substrate and the second substrate disposed thereon. A liquid crystal display device comprising: a columnar spacer to be held.