JPH08122753A - Active matrix liquid crystal display device - Google Patents

Abstract

PURPOSE: To obtain a liquid crystal display element which is capable of maintaining an adequate gap length and displaying high-grade images even if spacers exist on TFTs by forming recessed parts on a counter substrate in correspondence to projecting parts formed of active elements opposite to the active elements on an array side substrate. CONSTITUTION: Transparent pixel electrodes 3 arranged in a matrix form and the TFTs 4 as switching elements for driving these pixel electrodes 3 are arranged on the array side substrate 1. A stepped member 21 consisting of transparent insulating films is formed on the counter substrate 2 and the recessed parts corresponding to the projecting parts formed by the switching elements on the array side substrate 1 are formed on the surface of the counter substrate 2, i.e., the surface of an oriented film 7 by the thickness of the stepped member 21. Then, the distances between the oriented films 5 and 7 in the positions on the TFTs 4 and the distances between the oriented films 5 and 7 on the pixel electrodes 3 are substantially equaled to each other. Then, the spacers 9 existing on the TFTs 4 are adequately housed in the recessed parts formed on the counter substrate 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display element, and more particularly to an active matrix type liquid crystal display element having an appropriate liquid crystal layer thickness.

[0002]

2. Description of the Related Art FIG. 4 shows a sectional structure of a conventional TFT (thin film transistor) liquid crystal display element. As shown
This TFT liquid crystal display element is composed of a transparent array-side substrate 1 made of glass or the like, a counter substrate 2 arranged to face the array-side substrate, and a liquid crystal 8 sealed between the substrates 1 and 2. ing.

On the array side substrate 1, transparent pixel electrodes 3 arranged in a matrix and TFTs 4 as an active matrix element for driving the pixel electrodes 3 are arranged. Furthermore, covering the pixel electrode 3 and the TFT 4,
The interlayer insulating film 16 is formed, and the alignment film 5 made of polyimide or the like is formed on the interlayer insulating film 16.

A counter electrode 6 is formed on the surface of the counter substrate 2 facing the pixel electrode 3, and an alignment film 7 made of polyimide or the like is formed so as to cover the counter electrode 6.

The array side substrate 1 and the counter substrate 2 have an alignment film 5
And 7 are sealed with a frame-shaped seal material (not shown) at the peripheral edge so that they face each other with a predetermined gap length.
A liquid crystal 8 is filled in a gap portion formed by the sealing material and the alignment films 5 and 7. In order to match the distance between the alignment films 5 and 7, that is, the thickness of the layer of the liquid crystal 8 in the display region with a predetermined gap length, a plurality of spacers 9 are dispersed between the alignment films 5 and 7. Are arranged.

The spacer 9 is, for example, spherical and has a substantially uniform diameter d of about 2 to 11 μm corresponding to the gap length.

[0007]

On the surface of the array side substrate 1, that is, on the alignment film 5, there is formed a convex portion of about 400 to 600 nm corresponding to the thickness (height) of the TFT 4 as shown in the figure. To be done. On the other hand, the surface of the counter substrate 2, that is, the alignment film 7 is substantially flat. Therefore, the distance between the alignment films 5 and 7 at the position of the TFT 4 and the distance between the alignment films 5 and 7 at other positions are different by about 400 to 600 nm.

Therefore, as shown in the figure, the spacer 9 is T
When located on the FT 4, the spacer 9 on the TFT 4 substantially defines the thickness of the liquid crystal 8, that is, the gap length, and the gap length between the pixel electrode 2 and the counter electrode 6 exceeds an appropriate value. . If the gap length is not an appropriate value, the spacers 9 float and cause misalignment of the liquid crystal 8, and, for example, in the case of TN (twisted nematic) -TFT liquid crystal, regions (domains) having different alignment states occur. As a result, problems such as deterioration of display quality occur. Also,
If the gap length is forcibly secured, the spacer 9 presses the TFT 4 and destroys it, which causes a display defect.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal display element capable of maintaining an appropriate gap length by a spacer and displaying a high-quality image.

[0010]

In order to achieve the above-mentioned object, an active matrix type liquid crystal display element according to a first aspect of the present invention has a switching element and a pixel electrode connected to the switching element in a matrix form. A first substrate having a convex portion corresponding to the switching element formed on the surface thereof, and a counter electrode disposed so as to face the first substrate and to face the pixel electrode. And a liquid crystal arranged between the first and second substrates, a liquid crystal arranged between the first and second substrates, and a second substrate in which a concave portion facing the convex portion is formed on the surface portion. Spacers,
It is characterized by including.

It is preferable that the height of the convex portion and the depth of the concave portion are set to be substantially equal to each other so that the spacer positioned on the convex portion can be accommodated in the concave portion.

In order to form a concave portion facing the convex portion, a step member having a predetermined thickness may be selectively provided,
Further, the thickness of the color filter may be adjusted.

An active matrix type liquid crystal display element according to a second aspect of the present invention includes an array side substrate,
Switching elements formed in a matrix on the array-side substrate, pixel electrodes formed in a matrix connected to the corresponding switching elements on the array-side substrate, covering the switching elements and the pixel electrodes. A first alignment film formed and having irregularities corresponding to the switching elements, a counter substrate arranged to face the array side substrate, a counter electrode formed on the counter substrate, and the counter substrate. A second alignment film formed so as to cover the first alignment film and having irregularities corresponding to the irregularities of the first alignment film; and a plurality of spacers arranged between the first alignment film and the second alignment film. And the distance between the first and second alignment films is substantially equal over the entire surface.
It is characterized by the following.

[0014]

According to the above structure, the recess is formed in the opposing substrate corresponding to the protruding portion inevitably formed by the switching element. Therefore, when the spacer is located above the switching element, the spacer is housed in the step or the recess on the side of the opposing substrate, and a liquid crystal display element having a predetermined gap length can be obtained.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a cross-sectional structure of a main part of a liquid crystal display element according to an embodiment of the present invention. 1, the same parts as those in FIG. 4 are designated by the same reference numerals.

As shown in the figure, the TFT liquid crystal display device of this embodiment comprises a transparent array side substrate 1 made of glass or the like and a counter substrate 2 arranged so as to face the array side substrate 1.
And a liquid crystal 8 sealed between the substrates 1 and 2.

On the array side substrate 1, transparent pixel electrodes 3 arranged in a matrix and TFTs 4 as switching elements for driving the pixel electrodes 3 are arranged.
Further, an interlayer insulating film 16 is formed so as to cover the pixel electrode 3 and the TFT 4, and an alignment film 5 made of polyimide or the like is formed on the interlayer insulating film 16.

The TFT 4 includes a gate electrode 11 formed on the array-side substrate 1, a gate insulating film 12 covering the gate electrode 11, and an a-Si formed on the gate insulating film 12 so as to face the gate electrode 11. The i-type semiconductor film 13 made of (amorphous silicon) and the like, and the source electrode 14 and the drain electrode 15 connected to the side portion of the i-type semiconductor film 13 via an ohmic contact layer. The pixel electrode 3 is formed on the gate insulating film 12 and has a corresponding T
It is connected to the source electrode 14 of FT4.

The TF on the array substrate 1 is on the counter substrate 2.
A step member 21 made of a transparent insulating film such as SiO2 or SiN is formed except for the portion facing T4. The thickness of the step member 21, that is, the depth of the concave portion formed on the counter substrate 2 side is substantially equal to the height of the convex portion formed by the TFT 4 on the array side substrate 1, and is, for example, about 400 to 600 nm.

The counter electrode 6 is formed so as to cover the step member 21, and the alignment film 7 is formed on the counter electrode 6.

The array-side substrate 1 and the counter substrate 2 are sealed at their peripheral edges by a frame-shaped sealing material (not shown). A liquid crystal 8 is filled in a gap portion formed by the sealing material and the alignment films 5 and 7. The distance between the alignment films 5 and 7,
That is, in order to make the gap length a predetermined value, for example, a plurality of spherical spacers 9 are dispersedly arranged between the alignment films 5 and 7. The spacer 9 has a substantially uniform diameter d of about 2 to 11 μm corresponding to the gap length.

In addition to the configuration shown in FIG. 1, if necessary,
A polarizing plate, a reflector, a backlight, etc. are arranged.

According to this structure, a concave portion corresponding to the convex portion on the array-side substrate 1 is formed on the surface of the counter substrate 2, that is, the surface of the alignment film 7. Therefore, the distance d between the alignment films 5 and 7 at the position on the TFT 4 and the distance d between the alignment films 5 and 7 at the position on the pixel electrode 3 are substantially equal. Therefore, as shown in the figure, the spacers 9 located on the TFTs 4 are properly accommodated in the recesses formed in the counter substrate 2. Therefore, as shown in FIG. 1, the spacer 9 is a TFT.
4, the gap length does not exceed a predetermined value (design value) by this spacer, and a high quality image can be displayed.

The liquid crystal display device having the structure shown in FIG. 1 is manufactured, for example, by the following steps. First, the array side substrate 1
The TFT 4 and the pixel electrode 3 are formed on the upper surface by using a normal process. Next, the interlayer insulating film 6 and the alignment film 5 are sequentially stacked to cover the TFT 4 and the pixel electrode 3. An insulating film of SiO2, SiN or the like is formed on the counter substrate 2 by CVD or the like.
~ 600 nm is deposited. A portion of the insulating film facing the TFT 4 is patterned and removed by a photolithography process to form a step member 21. A counter electrode made of ITO or the like is deposited on the entire surface of the counter substrate 2 by sputtering or the like, and an alignment film 7 made of polyimide or the like is further formed thereon.

On the periphery of one of the substrates, a photo-curing resin or the like to be a sealing material is printed in a frame shape, and spacers 9 are scattered. Then, the matrix substrate 1 and the counter substrate 2 are bonded together. At this time, the spacer 9 located above the TFT 4 is housed in the concave portion of the counter substrate 2 so that a strong pressing force is not applied to the TFT 4. After that, the liquid crystal 8 is injected between the matrix substrate 1 and the counter substrate 2 by using a vacuum injection method or the like to complete the liquid crystal display element.

In the configuration of FIG. 1, the concave portion on the side of the counter substrate 2 is formed by the step member 21, but, for example, as shown in FIG. 2, the portion of the counter substrate 2 facing the TFT 4 is etched to form the counter substrate 2. You may form a recessed part in itself.

Further, in the case of a color liquid crystal display element using the color filter CF, instead of the step member 21, as shown in FIG. 3, R (red), G (green) and B (blue) color filters CF are used. The thickness may be adjusted so as to approximately match the height of the convex portion of the alignment film 5, and a concave portion having an appropriate size may be formed. In this case, a black black matrix (black mask) BM for blocking light leakage is arranged between the color filters CF of the counter substrate 2 and the color filters C are arranged.
It is desirable to match the difference between the thickness of F and the thickness of the black mask BM with the height of the convex portion formed by the TFT 4. Further, it is desirable to dispose the insulating protective film 23 between the counter electrode and the color filter CF.

The black matrix BM does not necessarily have to be provided. In that case, the thickness of the color filter CF itself is matched with the height of the convex portion. Note that, also in the configuration of FIG. 1, a black mask may be arranged between the step members 21.

In the above embodiment, the height of the convex portion of the array substrate and the depth of the concave portion of the counter substrate are made substantially equal, but the depth of the concave portion may be slightly larger than the height of the convex portion. Although the TFT 4 is shown as the active element in the above embodiment, MIM or the like may be used. The present invention can be applied to various liquid crystal display elements using spacers and active elements such as TN liquid crystal display elements, STN liquid crystal display elements, ferroelectric liquid crystal display elements, and polymer dispersed liquid crystal display elements.

[0030]

As described above in detail, according to the present invention, the concave portion is formed on the counter substrate so as to face the active element on the array side substrate and correspond to the convex portion formed by the active element. Therefore, it is possible to provide a liquid crystal display element capable of performing a high quality display by forming an appropriate gap length with a spacer. Further, since the interval between the alignment films facing each other is fixed, an appropriate gap length can be maintained even when the spacer is located on the active element.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a main part of an active matrix liquid crystal display element according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a main part of an active matrix type liquid crystal display element according to another embodiment of the present invention.

FIG. 3 is a sectional view showing a configuration of a main part of an active matrix type liquid crystal display element according to still another embodiment of the present invention.

FIG. 4 is a sectional view schematically showing a configuration of a main part of a conventional active matrix type liquid crystal display element.

[Explanation of symbols]

1 ... Array side substrate, 2 ... Counter substrate, 3 ... Pixel electrode, 4 ...
TFT (thin film transistor), 5, 7 ... Alignment film, 6 ... Counter electrode, 8 ... Liquid crystal, 9 ... Spacer, 21 ... Step member, 2
3 ... Insulating protective film, CF ... Color filter, BM ... Black matrix

Claims (6)

[Claims] 1. A first substrate having switching elements and pixel electrodes connected to the switching elements arranged in a matrix and having a convex portion corresponding to the switching element formed on a surface thereof; A second substrate which is disposed so as to face the first substrate, has a counter electrode which faces the pixel electrode, and has a concave portion which faces the convex portion formed on the surface portion; and the first and second substrates. An active matrix type liquid crystal display device comprising: a liquid crystal disposed between the first and second substrates; and a spacer disposed between the first and second substrates. 2. The active matrix type liquid crystal display device according to claim 1, wherein the height of the convex portion and the depth of the concave portion are substantially equal to each other. 3. The active matrix type liquid crystal display element according to claim 1, wherein the concave portion has a depth for accommodating a spacer located on the convex portion. 4. A step member having a predetermined thickness is selectively disposed on the second substrate, and the step member forms a recess. 2. The active matrix type liquid crystal display element described in 2 or 3. 5. A color filter having a predetermined thickness is selectively disposed on the second substrate, and a recess is formed by the color filter. 2. The active matrix type liquid crystal display element described in 2 or 3. 6. An array-side substrate, switching elements formed in a matrix on the array-side substrate, and pixel electrodes formed in a matrix connected to corresponding switching elements on the array-side substrate, A first electrode formed to cover the switching element and the pixel electrode, and has an unevenness corresponding to the switching element;
Alignment film, a counter substrate arranged to face the array-side substrate, a counter electrode formed on the counter substrate, and a concavo-convex pattern of the first alignment film formed to cover the counter substrate. A second alignment film having corresponding irregularities, and a plurality of spacers arranged between the first alignment film and the second alignment film, the first and second alignment films An active matrix liquid crystal display element, characterized in that the distance between them is formed substantially equal over the entire surface.