JPH11142870A - Transmission type liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type liquid crystal display element capable of improving picture quality by uniforming relation (VT characteristic) between voltage and a transmission factor and preventing the generation of short-circuit between transparent electrodes. SOLUTION: The transmission type liquid crystal display element 20 is provided with a transparent substrate 21, a counter substrate 22 arranged oppositely to the substrate 21 as a light exist side, transparent electrodes 23, 32 respectively formed on the substrates 21, 22, and a liquid crystal layer 34 formed in a gap between both the substrates 21, 22. A flattened film 31 is formed on the substrate 21 on the inside of the electrode 23. The surface of the film 31 is flattened by polishing processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission type liquid crystal display device which emits light from a transparent substrate to a counter substrate.

[0002]

2. Description of the Related Art In recent years, low power consumption, low voltage operation, light weight,
Liquid crystal displays characterized by thinness, color display, and the like are expanding their applications to personal computers and video equipment. Conventionally, as a liquid crystal display element for forming such a liquid crystal display, for example, FIG.
Is known. In FIG.
Denotes a transmissive liquid crystal display element (hereinafter abbreviated as a liquid crystal display element). The liquid crystal display element 1 employs an active matrix system, and includes a transparent substrate 2
Are arranged so as to face each other with a predetermined gap therebetween.

The transparent substrate 2 is made of quartz disposed inside a backlight (not shown) (light emission side), and includes a large number of transparent electrodes 4 formed for each pixel and these transparent electrodes 4. Are provided with switching elements 5 composed of thin film transistors (TFTs) for driving.

The switching element 5 includes a base 6 formed on the transparent substrate 2, a collector 7 formed on the base 6 via an insulating film (not shown), and a collector 7.
And a gate 8 formed on the side of the gate. The transparent electrode 4 is made of a transparent conductive material such as ITO formed by being electrically connected to the base 6 of the switching element 5, and an alignment film 9 made of polyimide or the like is formed on the surface of the transparent electrode 4. Is provided.

The transparent substrate 2 is provided with a first interlayer insulating film 10 and a second interlayer insulating film 11 when the switching element 5 is formed. These first interlayer insulating films 1
0, the second interlayer insulating film 11 is made of, for example, PSG (phosphosilicate glass), and is provided to electrically separate each component of the switching element 5 from other components or to electrically connect the components. It was done.

A planarizing film 12 is formed on the second interlayer insulating film 11.
Are formed. The flattening film 12 is made of BPSG (boron phosphorus silicate glass) or the like, and is a flattened by heat reflow treatment or a spin-coated transparent resist film. Then, as described above, the planarizing film 1 is formed.
Due to the formation of 2, the degree of unevenness particularly on the transparent substrate 2 caused by the switching element 5 is considerably reduced.

The opposing substrate 3 is disposed on the light emitting side, and has a transparent electrode 13 made of a transparent conductive film such as ITO and an orientation made of polyimide or the like on its inner surface (the surface on the transparent substrate 2 side). The films 14 are formed and arranged in this order. Also,
A liquid crystal layer 15 is provided in a gap between the transparent substrate 2 and the counter substrate 3. The liquid crystal layer 15 is uniaxially oriented by the orientation films 9 and 14, and its orientation changes when a voltage is applied between the transparent electrode 4 and the transparent electrode 13. . Thus, the transmission and blocking (absorption) of light incident from the backlight (not shown) via the transparent substrate 2 is adjusted by the liquid crystal layer 15.

[0008]

By the way, in such a liquid crystal display element 1, the liquid crystal display element 1 is flattened to some extent by the flattening film 12 due to the influence of the switching element 5 and various wirings (not shown). The flatness of the surface of the transparent electrode 4 is poor. Then, from the fact that in this way it has poor flatness of the transparent electrode 4 surface, in a liquid crystal layer 15 in a single pixel, and the thickness of the liquid crystal shown in Figure 4 in T ₁ T
Become different and the liquid crystal thickness indicated by _2, thereby V
The T characteristic is not uniform, and the transmittance is non-uniform within a single pixel.

That is, the transparent electrode 4 is affected by the influence of the base.
5 is not sufficiently flat, the thickness T ₁ of the liquid crystal in the peripheral portion of the transparent electrode 13 and the thickness T ₂ of the liquid crystal in the central portion of the single pixel differ from each other as shown in FIG. As a result, as shown in FIG. 6, the relationship (VT characteristic) between the voltage (V) between the transparent electrode 4 and the transparent electrode 13 and the transmittance (T) differs, and the transmittance at the same voltage is reduced. it from being different between the portion and the portion of the thickness T ₂ of the thickness T _1.

However, in recent years, as liquid crystal display devices have become ultra-miniaturized and ultra-high definition, poor uniformity of the VT characteristics in the pixels of the liquid crystal display element has an adverse effect on the image quality. This is one of the issues that need to be improved in quality. Also, if the uniformity of the plane of the transparent electrode is poor, the uniformity of contact between the alignment film and the buff roller is deteriorated when the alignment film on the transparent electrode is rubbed, and a large amount of buffing is locally generated to cause an adjacent pixel. The transparent electrodes may be short-circuited between them.

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the image quality by making the relationship between voltage and transmittance (VT characteristics) uniform and improve the short circuit between the transparent electrodes. An object of the present invention is to provide a transmissive liquid crystal display element in which the problem is prevented.

[0012]

According to the transmission type liquid crystal display device of the present invention, a transparent substrate, a counter substrate provided on the light emitting side facing the transparent substrate, and the transparent substrate and the counter substrate are respectively provided. A transparent electrode formed thereon, and a liquid crystal layer formed in a gap between the transparent substrate and the counter substrate, wherein the transparent substrate is provided with a flattening film inside the transparent electrode, Has solved the above-mentioned problem in that its surface is flattened by a polishing treatment.

According to this transmission type liquid crystal display device, the flattening film provided inside the transparent electrode on the transparent substrate is flattened by polishing the surface thereof. The degree of planarization is higher than that of a transparent resist film simply subjected to a heat reflow treatment or spin-coated, and therefore, the degree of planarization of the surface of a transparent electrode formed thereon is increased.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a transmission type liquid crystal display device of the present invention will be described in detail. FIG. 1 is a view showing one embodiment of a transmissive liquid crystal display element of the present invention.
Reference numeral 0 denotes a transmission type liquid crystal display element. This liquid crystal display element 20
Adopts an active matrix method similar to that shown in FIG.
2 are arranged so as to face each other with a predetermined gap therebetween.

The transparent substrate 21 is made of quartz disposed inside a backlight (not shown) (light emission side), and includes a large number of transparent electrodes 23 formed for each pixel and these transparent electrodes 23. Driving thin film transistor (TFT)
Are provided.

The switching element 24 includes a base 25 formed on a transparent substrate 21 in the same manner as shown in FIG.
And a collector 26 formed on the base 25 via an insulating film (not shown), and a gate 27 formed on the side of the collector 26. The transparent electrode 23 is a base 25 of the switching element 24.
The transparent electrode 23 is provided with an alignment film 28 made of polyimide or the like on the surface of the transparent electrode 23.

The transparent substrate 21 is provided with a first interlayer insulating film 29 and a second interlayer insulating film 30 when the switching element 24 is formed. The first interlayer insulating film 29 and the second interlayer insulating film 30 are made of PSG (phosphosilicate glass) or the like as shown in FIG. 4, and each component of the switching element 24 is replaced by another component. It is provided to be electrically separated from or electrically connected to.

A planarizing film 31 is formed on the second interlayer insulating film 30.
Are formed. The flattening film 31 is made of a spin-coated transparent resist film or BPSG (boron phosphorus silicate glass) or the like.
Alternatively, the surface is directly planarized by a polishing process such as a CMP (chemical mechanical polishing) method without performing a reflow process. Therefore, the flattening film 31 is thus formed.
Is flattened by the polishing process, so that the surface of the flattening film 31 is substantially flat without being affected by the irregularities on the transparent substrate 21 caused by the switching elements 24 and the like. .

The opposing substrate 22 is made of a transparent base material such as glass having the same structure as the opposing substrate 3 in the liquid crystal display element 1 shown in FIG. Transparent electrode 3 made of a transparent conductive film such as ITO
2. An alignment film 33 made of polyimide or the like is formed and arranged in this order. Further, a liquid crystal layer 34 is provided in a gap between the transparent substrate 21 and the counter substrate 22. The liquid crystal layer 34 also has the alignment films 28 and 33 as shown in FIG.
Are uniaxially oriented by a transparent electrode 2
When a voltage is applied between the transparent electrode 3 and the transparent electrode 32, the orientation direction is changed. And
Thus, the transmission and blocking (absorption) of the light incident from the transparent substrate 21 side is adjusted by the liquid crystal layer 34.

In the liquid crystal display element 20 having such a configuration,
Since the flattening film 31 provided inside the transparent electrode 23 of the transparent substrate 21 is flattened by polishing the surface, the conventional flattening film 31 is simply subjected to a heat reflow process or spin-coated. The flatness of the transparent resist film is higher than that of the transparent resist film, and thus the flatness of the surface of the transparent electrode 23 formed thereon is higher. Then, since in this way the surface of the transparent electrode 23 are sufficiently flat, it becomes uniform in a pixel thickness T ₃ of the single crystal layer 34 as shown in FIG. 2, thereby 3 As described above, the VT characteristics become uniform, and the transmittance becomes constant within a single pixel, so that the display quality can be improved. In addition, since the surface of the transparent electrode 23 is sufficiently flat, buffing does not locally accumulate when the alignment film 28 on the transparent electrode 23 is subjected to the rubbing treatment, so that the transparent electrodes are short-circuited between adjacent pixels. Can be effectively prevented.

[0021]

As described above, in the transmission type liquid crystal display device of the present invention, the flattening film provided inside the transparent electrode on the transparent substrate is flattened by polishing the surface thereof, whereby the conventional liquid crystal display device has the conventional structure. The flattening degree of the surface of the transparent electrode formed on the flattening film is increased because the flattening degree of the transparent electrode film formed on the flattening film is higher than that of the transparent resist film simply subjected to heat reflow treatment or spin-coated. Therefore, the thickness of the liquid crystal layer can be made uniform within the single pixel, whereby the VT characteristics can be made uniform, the transmittance can be made constant within the single pixel, and the display quality can be improved. Can be.

Also, since the surface of the transparent electrode is sufficiently flat, buffing does not locally accumulate when the alignment film on the transparent electrode is rubbed, so that the transparent electrodes are short-circuited between adjacent pixels. Can be effectively prevented. Therefore, since the interval between the transparent electrodes can be reduced, the domain margin can be improved.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a main part of a schematic configuration of an embodiment of a transmission type liquid crystal display element according to the present invention.

FIG. 2 is a side sectional view for explaining a function of the transmission type liquid crystal display element shown in FIG. 1;

3 is a graph showing V-T characteristics of T ₃ portion shown in FIG.

FIG. 4 is a sectional side view of a main part showing a schematic configuration of an example of a conventional transmission type liquid crystal display element.

FIG. 5 is a side sectional view for explaining a problem of the transmission type liquid crystal display element shown in FIG. 4;

6 is a graph showing a V-T characteristic of the T ₁ portion and T ₂ portion shown in FIG.

[Explanation of symbols]

Reference Signs List 20: transmissive liquid crystal display element, 21: transparent substrate, 22: counter electrode, 23: transparent electrode, 31: flattening film, 32: transparent electrode, 34: liquid crystal layer

Claims (1)

[Claims] 1. A transparent substrate, an opposing substrate provided on the transparent substrate and serving as a light emitting side, transparent electrodes respectively formed on the transparent substrate and the opposing substrate, and a transparent substrate and an opposing substrate. And a liquid crystal layer formed in a gap between the transparent substrate and the transparent substrate, wherein a flattening film is provided inside the transparent electrode, and the flattening film has a surface flattened by a polishing process. Characteristic transmission type liquid crystal display device.