JPH11183929A - Liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display element having an excellent display performance, a wide numerical aperture, a high yield, and high reliability. SOLUTION: A hole part arranged in an insulating layer to electrically connect an image electrode 17 with a switching element 14 is formed in a curved surface in the edge part 24, and when an average radius of curvature of the edge part 24 sectional form is made to r, and an average thickness of the insulating layer is made to d, r is in a range of larger than d/10 and smaller than 10d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, it has been desired to improve the aperture ratio in order to increase the brightness and reduce the power consumption of a liquid crystal display device using a thin film transistor (hereinafter referred to as TFT). One of the structures that can increase the aperture ratio is to cover the scanning lines and signal line wiring of the active matrix substrate and the TFT that is a switching element with an insulating layer, and to surround the pixel electrode with the scanning line surrounding the pixel. 2. Description of the Related Art A structure in which a signal line is extended over a signal line is known. In the structure in which the pixel electrode is formed on the insulating film, a hole, for example, a contact hole formed by a photolithographic method or the like is provided in the insulating film in order to connect the pixel electrode and the switching element.

The pixel electrode and the switching element are connected via the contact hole, and the reliability of the connection largely depends on the shape of the edge part. That is, when the edge portion of the contact hole has a conventional shape having a vertical or steep angle, a microscopic discontinuous surface such as a crack occurs in the overlying connection conductive film (for example, ITO transparent conductive thin film). It was confirmed that the connection resistance deteriorated or a contact failure occurred, and a display failure such as a point defect occurred.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device having a wide aperture ratio, good display performance, high yield and high reliability. I do.

[0005]

A first embodiment of a liquid crystal display device according to the present invention is a substrate, a switching element disposed on a main surface of the substrate, and a scanning device connected to the switching element and arranged in a matrix. Lines and signal lines, an insulating layer covering at least the switching element, the scanning line, and the signal, a pixel electrode disposed on the insulating layer, and an electrical connection between the pixel electrode and the switching element. An active matrix substrate having holes arranged in the insulating layer, a substrate, a counter substrate including a common electrode disposed on a main surface of the substrate, an active matrix substrate and the counter substrate, In the liquid crystal display element having the liquid crystal material disposed in the gap, the hole has a curved edge shape of the insulating layer in the hole, and the edge has a cross-sectional shape. And Hitoshikyoku radius r, when the average thickness of the insulating layer was set to d, r is characterized in that within the following range d / 10 or more 10d.

In a second embodiment of the liquid crystal display device according to the present invention, the curved surface of the edge of the insulating layer in the hole has a surface of d / 50.
It is characterized in that the following minute irregularities are arranged. In a third mode of the liquid crystal display device according to the present invention, the curved surface of the edge of the insulating layer in the hole has a radius of curvature of 0.1 μm to 100 μm.
m. A fourth embodiment of the liquid crystal display device according to the present invention is characterized in that the insulating layer has a function of a colored layer.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a liquid crystal display device, as shown in FIG.
For example, it is important to connect the ITO transparent conductive thin film and the switching element under the insulating layer 1 with low resistance and high reliability. If the edge portion 3 of the contact hole portion is sharply sharp as shown in FIG. 3, sharply constricted (so-called reverse taper shape), or bent at an angle as shown in FIG. Due to the difference in the thermal expansion coefficient between the insulating layer 1 and the ITO and the active element terminals due to the heat and mechanical stress in the medium and use environment, and the difference in the elastic modulus, the ITO
Problems such as poor connection resistance and poor connection occur. On the other hand, as shown in FIGS. 1 and 2, if the shape of the edge portion 3 of the contact hole is a curved surface and the cross-sectional shape is d, the average thickness of the insulating layer 1 is d / 10 ≦ r ≦ 10d. If so, the deterioration of the ITO connection resistance and the connection failure due to the above-mentioned heat and mechanical stress do not occur, and there is no problem in reliability. Further, as shown in FIG. 2, by providing the edge portion 3 of the contact hole with minute unevenness of d / 50 or less, the adhesion between the edge portion 3 and a contact conductive layer such as ITO is improved, and high reliability is obtained. Can be Note that the average radius of curvature indicates the average value of the entire radius of the radius of curvature rn when the edge 3 of the contact hole portion is viewed in a minute range,

[0008]

(Equation 1) Indicated by

The inventor has confirmed that when the average radius of curvature of the cross-sectional shape of the edge portion of the contact hole is smaller than d / 10, the edge portion becomes almost the same as the sharply sharp edge portion, and the reliability is reduced due to thermal stress or the like. The radius of curvature is 10
The present inventor has confirmed that, when d is larger than d, the shape of the contact hole becomes too large, causing a decrease in the aperture ratio and deteriorating the characteristics. Therefore, the average radius of curvature r of the edge portion of the contact hole portion is d / 10 ≦ r ≦ 10r, which is a range where good display characteristics and highly reliable contact can be obtained.
Practically, it was confirmed that good display characteristics can be obtained in almost all liquid crystal display elements when the cross-sectional shape of the edge portion 3 of the insulating layer 1 in the contact hole has a curvature radius of 0.1 μm or more and 100 μm or less.

Further, as shown in FIG. 2, if the edge portion 3 of the insulating layer 1 of the contact hole has minute irregularities, the adhesion of the contact conductive layer to the contact hole is improved.
The present inventor has confirmed that if the irregularities are larger than d / 50, local stress due to heat or the like is likely to accumulate, causing a contact failure. Therefore, it is preferable that the minute unevenness on the edge 3 of the insulating layer 1 in the contact hole is d / 50 or less.

The control of the average radius of curvature of the cross-sectional shape of the edge portion 3 of the contact hole can be controlled by the exposure conditions of photolithography, etching conditions, and the material of the insulating layer 1.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a liquid crystal display device using the present invention will be described below in detail. (Embodiment 1) FIG. 5 is a schematic sectional view of a liquid crystal display device according to an embodiment of the present invention.

FIG. 6 is a schematic plan view of an embodiment of the present invention on the array substrate side. The array substrate side is shown in FIG.
3 is a cross-sectional view taken along the line A′-A ″ -A ″ ′ of FIG.
The film formation and patterning are repeated in the same manner as in the process of forming, and the thin film transistor serves as the signal line 11, the gate line 12 serving as a scanning line, the electrode wiring of the accumulation capacity line 13, and the source electrode of the TFT 14 and the electrode of the storage capacity. Electrodes 15 are formed on the main surface of the glass substrate 21 to form 400 pixels, 640 pixels in width,
A polysilicon TFT array substrate having a pixel pitch of 300 μm was formed. An insulating layer 22 of acrylic resin is applied on the TFT array of the substrate 21 so as to have a thickness of 3 μm.
A contact hole 23 was opened at 17 by a photolithography method, and then an ozone plasma treatment was performed. The edge portion 24 of the contact hole 23 was a curved surface, the average radius of curvature of the cross section was about 3 μm, and the edge portion 24 had minute irregularities of 0.02 μm or less. A pixel electrode 17 was formed thereon by forming a 1500 angstrom film of ITO and patterning.

On the surface of the array substrate, AL-1051 (manufactured by Nippon Synthetic Rubber Co., Ltd.) is applied as a material for an alignment film to a thickness of 1000 angstroms, and a rubbing process is performed in the alignment process direction 19 to obtain an alignment film (shown in the drawing). Was formed.

Next, AL-1051 (trade name) is similarly coated as an alignment film on a counter substrate 31 having a main surface on which a counter electrode 32 made of a red, green, and blue color filter and ITO as a common electrode is formed. Rubbing was performed and an adhesive was printed around the substrate.

Next, the substrates were arranged such that the alignment films of the array and the opposed substrates faced each other, and the rubbing directions were 90 degrees, and the substrates were bonded by heating to cure the adhesive. Next, CN was added to ZLI-4792 (manufactured by E. Merck) as a liquid crystal composition in an amount of 0.3 W from the injection port by a usual method.
The one added with t% was injected, and thereafter the injection port was sealed.

The color display type active matrix liquid crystal display element formed in this way can provide good display and has been subjected to a temperature cycle test of −20 ° C. →→ 60 ° C. 100 times. Good display was obtained without occurrence of defects such as defects. 33 indicates a gate insulating film, 34 indicates an undercoat layer, and 35 indicates an auxiliary capacitor.

Embodiment 2 FIG. 7 is a schematic sectional view of a liquid crystal display device according to one embodiment of the present invention. In the same manner as in Example 1, the electrode wiring 11 and the TFT 14 were formed on the main surface of the glass substrate, and the color filters 42, 43, and 44 provided with the contact holes 23 also serving as insulating layers on the surface were formed with a thickness of 4 μm. . The edge portion of the contact hole 23 was a curved surface, and the average radius of curvature of the cross section was 5 μm, and had fine irregularities of 0.04 μm or less. An ITO transparent conductive layer (not shown) of the pixel electrode 17 was formed thereon at 1000 Å. Next, the array substrate 41 and the counter substrate 31 having the common electrode 32 formed on the main surface were combined in the same manner as in Example 1 to produce a liquid crystal display element. The color display type active matrix liquid crystal display element formed in this way can obtain good display,
A temperature cycle test of −20 ° C. →→ 60 ° C. was performed 100 times, but no defect such as a point defect caused by a contact defect occurred and a good display was obtained.

(Comparative Example) FIG. 8 is a schematic sectional view of a liquid crystal display device according to a comparative example of the present invention. Electrode wirings 11 and 12 and TFT 14 are formed on the main surface of the glass substrate in the same manner as in the first embodiment, and an acrylic resin insulating film 22 is applied to the surface so as to have a thickness of 3 μm. A contact hole 23 was opened by the method. The edge of the contact hole 23 is almost vertically upright. A 1500 angstrom film of ITO (not shown) was formed thereon and patterned to form a pixel electrode 17.

On the surface of this array substrate, an alignment film AL-1051 (manufactured by Nippon Synthetic Rubber Co., Ltd.) was applied to a thickness of 1000 angstroms in the same manner as in Example 1, and a rubbing treatment was performed to form an alignment film. .

Next, AL-1051 (trade name) is similarly applied as an alignment film on a counter substrate having red, green and blue color filters and a common electrode ITO formed on the main surface, and rubbed. An adhesive was printed around the substrate.

Next, the substrates were arranged such that the alignment films faced each other and the rubbing directions were 90 degrees, and the substrates were bonded by heating to cure the adhesive. Next, ZLI-4792 was obtained as a liquid crystal composition from the injection port by a usual method.
(E. Merck) was added with 0.3 wt% of CN added, and then the inlet was sealed.

The color display type active matrix liquid crystal display element thus formed provided good display in the initial stage. However, when a temperature cycle test of -20.degree. C..fwdarw.60.degree. Many point defects occurred.

[0024]

According to the present invention, a sufficient reliability of the contact in the contact hole portion can be obtained, and a liquid crystal display device having a high opening ratio, high image quality and high reliability can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a contact hole portion according to an embodiment of the present invention.

FIG. 2 is a sectional view of a contact hole portion according to an embodiment of the present invention.

FIG. 3 is a sectional view of a contact hole portion of a comparative example (conventional example) of the present invention.

FIG. 4 is a sectional view of a contact hole portion of a comparative example (conventional example) of the present invention.

FIG. 5 is a schematic sectional view of a liquid crystal display device according to an example of the present invention.

FIG. 6 is a schematic plan view of a liquid crystal display device according to an example of the present invention.

FIG. 7 is a schematic sectional view of a liquid crystal display device according to an example of the present invention.

FIG. 8 is a schematic sectional view of a liquid crystal display device of a comparative example of the present invention.

[Explanation of symbols]

 1: insulating layer 2: pixel electrode 3: contact hole (hole) 11: signal line 12: gate line (scanning line) 22: insulating layer 23: contact hole (hole) 24: edge

Claims (4)

[Claims] 1. A substrate, a switching element disposed on a main surface of the substrate, a scanning line and a signal line connected to the switching element and arranged in a matrix, and the switching element, the scanning line, and the signal line. An active matrix comprising: an insulating layer that covers at least a pixel electrode disposed on the insulating layer; and a hole disposed in the insulating layer for electrically connecting the pixel electrode and the switching element. A liquid crystal display device comprising: a substrate; a substrate; a counter substrate including a common electrode disposed on a main surface of the substrate; and a liquid crystal material disposed in a gap between the active matrix substrate and the counter substrate. In the hole, the edge portion shape of the insulating layer of the hole portion is a curved surface shape, the average curvature radius r of the edge portion cross-sectional shape, the average thickness of the insulating layer When a, r is a liquid crystal display element, characterized in that within the following range d / 10 or more 10d. 2. The liquid crystal display device according to claim 1, wherein the curved surface of the edge portion of the insulating layer in the hole has fine irregularities of d / 50 or less. 3. The liquid crystal display device according to claim 1, wherein the curved surface of the edge portion of the insulating layer in the hole has a radius of curvature in a range of 0.1 μm to 100 μm. 4. The liquid crystal display device according to claim 1, wherein the insulating layer has a function of a colored layer.