KR100786835B1 - Liquid crystal display and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a liquid crystal display device in which a voltage holding ratio (VHR) is maintained well by providing an impurity blocking film that blocks impurities from a transparent conductive film from penetrating into the liquid crystal space, and a method of manufacturing the device. The display element includes a semiconductor substrate on which a semiconductor integrated circuit is formed; A transparent substrate disposed spaced apart from the semiconductor substrate and having a transparent conductive film formed on one side thereof; An impurity blocking film provided on the transparent conductive film; An alignment film provided on the impurity blocking film; A liquid crystal material disposed between the transparent substrate and the semiconductor substrate; And a plurality of reflective electrodes disposed on the semiconductor integrated circuit and connected to the semiconductor integrated circuit, wherein the impurity blocking film is formed by treating a surface of the transparent conductive film with CF ₄ plasma.

LCD, ELCOS, Liquid Crystal, Impurity, Block, Plasma, CF4, VHR

Description

Liquid crystal display and its manufacturing method {LIQUID CRYSTAL DISPLAY AND MANUFACTURING METHOD THEREOF}

1 is a cross-sectional view of a transmissive liquid crystal display device according to an exemplary embodiment of the present invention.

2 is a block diagram illustrating a device manufacturing method of FIG. 1.

3 is a cross-sectional view of a reflective liquid crystal display device according to another exemplary embodiment of the present invention.

4 is a block diagram illustrating a device manufacturing method of FIG. 3.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display (LCD). More particularly, the present invention provides an impurity blocking film that blocks impurities from a transparent conductive film from penetrating into the liquid crystal space, thereby providing a good voltage holding ratio (VHR). And a method for manufacturing the device.

In general, liquid crystal display devices can be driven with low power consumption and low voltage, and have advantages such as thinness and light weight, and thus are used in display devices of portable electronic products such as notebook computers, small televisions, electronic clocks, and calculators.

Such liquid crystal display devices are usually formed by injecting liquid crystals between two parallel conductive substrates. When a voltage is applied to the conductive substrates, the liquid crystal is changed in an arrangement direction by a voltage change applied to the conductive substrate, The light emitted from the reflecting plate is transmitted or blocked by the substrate according to the arrangement of the liquid crystal, thereby to transmit a predetermined letter or number or an arbitrary image to the user.

Such liquid crystal display devices are generally classified into a transmissive type and a reflective type. Among the above-mentioned reflective liquid crystal display devices, in recent years, so-called Elcos (LCOS; Liquid Crystal On Silicon, hereinafter referred to as LCOS) configured to realize a micro display is called. Reflective liquid crystal display devices have attracted attention.

The LCOS is a liquid crystal display device formed by disposing a liquid crystal material between a semiconductor substrate and a glass substrate. Unlike a conventional liquid crystal display device, a cell is formed on a semiconductor substrate. Since it can be easily disposed, it has the advantage that it can be miniaturized.

Looking at the conventional structure of the LCOS in detail, a semiconductor integrated circuit is formed on a semiconductor substrate, a liquid crystal material is injected between the semiconductor substrate and the transparent glass substrate.

A transparent conductive film such as ITO is formed on an inner surface of the glass substrate, and a plurality of reflective electrodes holding a predetermined pattern are formed on an inner surface of the semiconductor substrate, and the reflective electrodes are electrically connected to the semiconductor integrated circuit.

The semiconductor integrated circuit includes a source electrode, a drain electrode, and a gate electrode formed on the semiconductor substrate with the source electrode, the drain electrode formed therebetween. In this case, the drain electrode is electrically connected to a connection electrode connected to the reflective electrode, and a capacitor is disposed adjacent to the gate electrode. Of course, the gate electrode, the connecting electrode, and the capacitor are separated from each other by an insulating layer, and a passivation layer may be further formed on the insulating layer.

Accordingly, the LCOS formed as described above serves as a reflective liquid crystal display by reflecting light incident through the transparent substrate at the reflective electrode while using the transparent conductive film as the common electrode and the reflective electrode as the pixel electrode.

In the above, the LCOS using the semiconductor substrate as the back substrate has been described as an example, but the LCOS may use a glass substrate coated with an aluminum film as the back substrate instead of the semiconductor substrate.

By the way, the transmissive and reflective (particularly LCOS) liquid crystal display elements having the above-described configuration generally improve the voltage holding ratio (VHR) as the impurity content in the liquid crystal is smaller.

Therefore, a process for removing impurities is performed before the liquid crystal injection process. As an example of such a process, Korean Patent Laid-Open No. 2001-57018 discloses a method of surface treating a pixel electrode with SF ₆ plasma.

In the SF ₆ plasma treatment process, when the transparent conductive film is etched to form a pixel electrode, the transparent conductive film is plasma-processed to make the surface of the transparent conductive film in a stable state, thereby removing the photoresist and a component of the strip for removing the photoresist. And components of the transparent conductive film do not react.

According to the element manufacturing method of such a structure, generation | occurrence | production of an organic foreign material is suppressed in the transparent conductive film or the pixel electrode formed by etching this film in the manufacturing process of a liquid crystal display element.

However, the conventional device fabrication method configured as described above has a problem in that it is possible to suppress organic foreign matters generated during the manufacturing process of the pixel electrode, while impurity generated during use of the liquid crystal display device cannot be suppressed.

That is, indium tin oxide (ITO) forming a transparent conductive film, impurities such as indium ions are generated during use of the liquid crystal display, and these impurities penetrate into the liquid crystal. Therefore, the VHR having an inverse relationship with the impurity content is reduced, resulting in a decrease in contrast, which ultimately reduces the lifetime of the device.

Accordingly, the present invention has been made to solve the above problems, and provides a liquid crystal display device having a good voltage holding ratio (VHR) by providing an impurity blocking film that blocks impurities from the transparent conductive film from penetrating into the liquid crystal space. There is a purpose.

Another object of the present invention is to provide a method for producing a liquid crystal display device.

The above object of the present invention is achieved by a liquid crystal display device provided with an impurity blocking film on a transparent conductive film. Here, the liquid crystal display device may be configured in a general transmissive and reflective type, in particular, the reflective liquid crystal display device may be made of LCOS including a semiconductor substrate provided with a semiconductor integrated circuit. The impurity barrier film is formed by surface treatment of a transparent conductive film with CF ₄ plasma.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view showing a liquid crystal display device according to an embodiment of the present invention, in particular a transmissive liquid crystal display device. As shown in the drawing, the transmissive liquid crystal display device of the present embodiment includes two glass substrates 10 and 12 disposed in a state of facing each other and a transparent conductive film provided on inner surfaces of the glass substrates 10 and 12 facing each other, respectively. (14, 16), the impurity blocking film 18 provided on the transparent conductive films 14, 16, the alignment film 20 provided on the impurity blocking film 18, and the liquid crystal injected into the alignment film 20. Material 22. Here, the transparent conductive films 14 and 16 are made of ordinary indium tin oxide (ITO).

The impurity blocking film 18 is to prevent impurities such as indium ions generated in the transparent conductive films 14 and 16 from penetrating into the liquid crystal space through the alignment film 20 while the liquid crystal display device is in use. Is composed of an In-F film or a CF film.

Hereinafter, a method of manufacturing the device of the above embodiment will be described with reference to FIGS. 1 and 2.

First, transparent conductive films 14 and 16 are respectively provided on two inner surfaces of the glass substrates 10 and 12 (ST 10). In this case, the transparent conductive layers 14 and 16 are formed by printing indium tin oxide (ITO). Next, the glass substrates 10 and 12 are disposed in a chamber (not shown) in which CF ₄ and O ₂ are filled at a ratio of 50:50, and then the transparent conductive films 14 and 16 are surface treated with plasma ( ST20). In this way, an impurity blocking film 18 is formed on the transparent conductive films 14 and 16, and the impurity blocking film 18 is formed of an IN-F or CF film.

After the impurity blocking film 18 is formed as described above, the alignment film 20 is formed on the blocking film 18 (ST30), and the two glass substrates 10 and 12 are disposed to face the alignment film 20. The liquid crystal material 22 is injected into the ST40 and the alignment layer 20 to manufacture a liquid crystal display device (ST50). In this case, the alignment layer 20 may be made of polyimide or a dispersed liquid crystal solution, which is a polymer solution.

3 is a cross-sectional view of a liquid crystal display device according to another exemplary embodiment of the present invention. In particular, FIG. 3 illustrates an LCOS including a semiconductor substrate in a reflective liquid crystal display device.

The LCOS of the present embodiment is a liquid crystal material injected between a semiconductor substrate 30 on which a semiconductor integrated circuit 32 is formed, a transparent glass substrate 34 disposed opposite to the substrate 30, and both substrates 30 and 34. (36).                     

An inner surface of the glass substrate 34 is provided with a transparent conductive film 38 made of indium tin oxide (ITO) to serve as a common electrode, and the impurity blocking film 40 of the present invention is provided on the transparent conductive film 38. A normal alignment film 42 is provided on the impurity blocking film 40. At this time, the impurity blocking film 40 is made of an IN-F or C-F film as in the first embodiment of FIG.

In addition, a plurality of reflective electrodes 44 having a predetermined pattern are formed on an inner surface of the semiconductor substrate 30, and the reflective electrodes 44 are electrically connected to the semiconductor integrated circuit 32.

The semiconductor integrated circuit 32 includes a source 32a and a drain 32b formed in the semiconductor substrate 30, and a gate electrode 32c formed over the semiconductor substrate 30 with these interposed therebetween. In this case, the drain 32b is electrically connected to the connection electrode 46 connected to the reflective electrode 44, and a capacitor 48 is disposed adjacent to the gate electrode 32c. Of course, the gate electrode 32c, the connecting electrode 46, and the capacitor 48 are separated from each other by the insulating layer 50 so as to be in contact with each other, and the passivation layer formed of SiO ₂ or SiNx on the insulating layer 50. The base layer 52 may be further formed.

Thus, the LCOS formed as described above uses the transparent conductive film 38 as the common electrode and the reflective electrode 44 as the pixel electrode, and receives light incident through the glass substrate 34 from the reflective electrode 44. It reflects and acts as a reflective liquid crystal display.

A method of manufacturing the LCOS having the above-described configuration will be described with reference to FIGS. 3 and 4.

First, the transparent conductive film 38 is provided on the inner surface of the transparent glass substrate 34 (ST60). In this case, the transparent conductive film 38 is formed by printing indium tin oxide (ITO). Next, the glass substrate 34 is disposed in a chamber (not shown) in which CF ₄ and O ₂ are filled at a ratio of 50:50, and then the transparent conductive film 38 is surface treated with plasma (ST70). In this way, an impurity blocking film 40 is formed on the transparent conductive film 38, and the impurity blocking film 40 is formed of an IN-F or CF film.

After the impurity blocking film 40 is formed as described above, the alignment layer 42 is provided on the impurity blocking film 40 (ST80), and the semiconductor substrate 30 and the glass substrate 34 on which the semiconductor integrated circuit 32 is formed. The liquid crystal material 36 is injected between the substrates 30 and 34, and the LCOS is manufactured (ST 100).

According to the above embodiment, the impurity blocking film 40 provided in the transparent conductive film 38 prevents impurities such as indium ions generated from the transparent conductive film 38 from penetrating into the liquid crystal space during use of the liquid crystal display device. Done. In addition, surface roughness may be improved to uniformly form a cell gap.

According to the experimental results of the present inventors, the conventional liquid crystal display device without an impurity blocking film has an initial VHR of about 65 to 75%, but the liquid crystal display device of the present invention having an impurity blocking film is about 80 to 95%. I knew it existed. In addition, in the experiment for examining the amount of VHR change over time, the VHR of the conventional liquid crystal display device is lowered to less than 20% after 200 hours, whereas the liquid crystal display device of the present invention maintains VHR of 60% or more. I could see that. In the above experiment, the surface treatment step of the CF ₄ plasma proceeded at a frequency of 60 to 200 Hz and a power of 200 to 600 W for about 20 to 40 sec.

Moreover, as a result of measuring the surface roughness of a transparent conductive film, it turns out that the conventional liquid crystal display element which does not have an impurity blocking film has a roughness value of 43.5, whereas the liquid crystal display element of this invention has a roughness value of 25-35. Could.

In the above, the LCOS having a semiconductor substrate has been described as an example. However, the present invention has a lower glass substrate coated with an aluminum film, and it is obvious that the present invention can be applied to an LCOS having a CMOS circuit on the lower glass substrate.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the scope of the invention.

As described above, the transmissive and reflective liquid crystal display device of the present invention, in which an impurity blocking film was formed by surface treatment of a transparent conductive film with CF ₄ plasma, showed an initial VHR superior to that of a conventional liquid crystal display device. VHR variation also showed satisfactory results. Therefore, a decrease in contrast ratio due to VHR reduction can be suppressed, and device life can be extended.

In addition, since the surface roughness of the transparent conductive film is improved, the cell gap can be kept constant, thereby improving the retardation.

Claims (10)

Two glass substrates disposed to face each other; Transparent conductive films provided on inner surfaces of the glass substrate facing each other; An impurity blocking film provided on the transparent conductive film; An alignment film provided on the impurity blocking film; A liquid crystal material injected into the alignment layer; Liquid crystal display device comprising a. The liquid crystal display device of claim 1, wherein the transparent conductive film is made of indium tin oxide (ITO). The liquid crystal display device according to claim 1 or 2, wherein the impurity blocking film is made of an In-F film or a C-F film. A semiconductor substrate on which a semiconductor integrated circuit is formed; A transparent substrate disposed spaced apart from the semiconductor substrate and having a transparent conductive film formed on one side thereof; An impurity blocking film provided on the transparent conductive film; An alignment film provided on the impurity blocking film; A liquid crystal material disposed between the transparent substrate and the semiconductor substrate; A plurality of reflective electrodes disposed over the semiconductor integrated circuit and connected to the semiconductor integrated circuit; Liquid crystal display device comprising a. The liquid crystal display device of claim 4, wherein the transparent conductive film is made of indium tin oxide (ITO). The liquid crystal display device according to claim 4 or 5, wherein the impurity blocking film is made of an In—F film or a C—F film. The liquid crystal display of claim 6, wherein the semiconductor integrated circuit comprises a source and a drain formed in the semiconductor substrate and a gate electrode formed on the semiconductor substrate, and the drain is electrically connected to the reflective electrode. Providing two transparent conductive films on inner surfaces of the two glass substrates; Surface treating the transparent conductive film on the glass substrate with CF ₄ plasma to form an impurity blocking film; Providing an alignment layer on the impurity blocking layer; Disposing two glass substrates so that the alignment layers face each other; Injecting a liquid crystal material into the alignment layer; Method of manufacturing a liquid crystal display device comprising a. Providing a transparent conductive film on an inner surface of the transparent glass substrate; Surface treating the transparent conductive film on the glass substrate with CF ₄ plasma to form an impurity blocking film; Providing an alignment layer on the impurity blocking layer; Assembling the glass substrate with a semiconductor substrate on which a semiconductor integrated circuit is formed; Injecting a liquid crystal material between both substrates; Method of manufacturing a liquid crystal display device comprising a. 10. The method of claim 8 or 9, wherein the surface treatment of the transparent conductive film with CF ₄ plasma is performed at a frequency of 60 to 200 Hz, 200 to 600 W in a gas atmosphere in which CF ₄ and O ₂ are mixed at a ratio of 50:50. The manufacturing method of the liquid crystal display element which advances about 20 to 40 second by electric power.

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