WO2003044594A1

WO2003044594A1 - Liquid crystal display having conductive pillar

Info

Publication number: WO2003044594A1
Application number: PCT/KR2002/002190
Authority: WO
Inventors: Eunjung Lem
Original assignee: Iljin Diamond Co., Ltd
Priority date: 2001-11-23
Filing date: 2002-11-22
Publication date: 2003-05-30
Also published as: TWI226496B; AU2002356454A1; KR20030042641A; TW200412457A

Abstract

The present invention is related to liquid crystal display, more specifically, liquid crystal display having conductive pillar. Liquid crystal display according to the present invention comprises a pair of transparent plates which are having both display area and seal area and are separated each other by cell gap; at least one pillar which height is equal to or higher than said cell gap; seal material which is applied into seal area surrounding display area and liquid crystal which is filled in display area.

Description

TITLE OF INVENTION

LIQUID CRYSTAL DISPLAY HAVING CONDUCTIVE PILLAR

TECHNICAL FIELD

The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display keeping distance between an upper substrate and a lower substrate as increasing conductivity of the upper and the lower substrate by using a conductive pillar and having a conductive pillar in the area of liquid crystal injecting hole so that the uniformity of injecting speed of liquid crystal can be achieved.

BACKGROUND ART

Generally, a liquid crystal display forms a switching element and a transparent pixel electrode in one substrate, and forms a transparent electrode opposite to the pixel electrode in another transparent substrate and combines the two substrates. Then, a liquid crystal is injected between the two substrates(hereinafter, the distance between the two substrates is called "a cell gap") to change optical anisotropy according to changes of an electric field.

Thus, liquid crystal display apparatus displays an image by transmitting light to the liquid crystal or cutting it off on the liquid crystal, thereby implementing lower power consumption than a monitor or a CRT with the advantage of lightness and compactness, and it is widely used for various purposes.

As for this type of the liquid crystal display, there are two types of liquid crystal displays: one is a simple matrix type using a liquid crystal panel, which inserts a liquid crystal between one pair of substrates formed with intersecting electrodes each other in each opposite side of one pair of substrates, and the other is an active matrix type using a liquid crystal panel having a switching element selected as a pixel unit in one of the substrates.

In the active matrix type of the liquid crystal display, there are two kinds of liquid crystal displays: a liquid crystal display(generally, it is called a TN-type active matrix liquid crystal display) in a vertical electric field way uses a liquid crystal panel where electrode groups for selecting pixels are formed on the upper and the lower substrate, respectively; and a liquid crystal display(generally, it is called an IPS-type liquid crystal display) in a horizontal electric field way uses a liquid crystal panel where electrode groups for selecting pixels are formed in one of the substrates.

The liquid crystal panel configuring the TN-type active matrix liquid crystal display orients a liquid crystal element to be twisted at 90 degrees between the one pair of the substrates, depositing two sheets of polarizers which arrange cross-Nicol in a direction of an absorption axis and make an absorption axis of a polarizer of an incident side parallel or orthogonal to a rubbing direction of an alignment layer of a liquid crystal element adjacent to the absorption axis, in outer sides of the upper and the lower substrate. In the TN-type active matrix liquid crystal display, when a voltage is not applied to a liquid crystal display layer, an incident light becomes a straight-line polarized light in the polarizer of the incident side, and the straight-line polarized light is spread according to a twist of the liquid crystal layer. If a transmission axis of a polarizer from an emission side is equal to an azimuth of the straight-line polarized light, all the straight-line polarized light is emitted to be a white image(what is called, normally open mode).

In addition, when a voltage is applied, a direction(director) of a unit vector showing an average oriented direction of a liquid crystal element axis goes toward a vertical direction with a substrate surface, and the azimuth of the straight-line polarized light from the incident side is not changed, therefore it is equal to the absorption axis of the polarizer of the emission side to become a black image(refer to "The Basics and Applications of Liquid Crystal" issued by Industrial Committee in 1991).

On the other hand, in the IPS-type liquid crystal display that forms electrode groups for selecting pixels and electrode wiring groups in one of the substrates and switches a liquid crystal layer within a surface parallel to surfaces of the substrates by applying a voltage between neighboring electrodes(pixel electrodes and oriented electrodes) on the substrates, a polarizer is aligned to display a black image when a voltage is not applied(what is called, normally close mode).

An element of the liquid crystal display layer in the IPS-type liquid crystal display has a homogeneous orientation parallel to the surfaces of the substrates, and a director of the liquid crystal layer in a plane parallel to the substrates becomes parallel to an electrode wiring direction or has a certain angle when a voltage is not applied. However, when a voltage is applied, director direction of the liquid crystal layer becomes vertical to the electrode wiring direction, and when the director direction of the liquid crystal layer is inclined to 45 degrees of the electrode wiring direction compared to the director direction without the applied voltage, the liquid crystal layer with the applied voltage rotates an azimuth of a vibration surface of a polarized light at 90 degrees just like a half wavelength plate. Then, the transmission axis of the polarizer from the emission side has the same azimuth as that of the vibration surface of the polarized light, displaying a white image.

The IPS-type liquid crystal display has a little change of colors or contrast even though a viewing angle is changed, and implements a wide range of angular fιeld(refer to Japanese Laid Open Patent No. 94-505247).

A color filter method is mainly used in drawing full color pictures of various liquid crystal displays. It divides pixels corresponding to one dot of a color image into 3, and aligns color filters corresponding to three primary colors such as red(R), green(G), and blue(B) in each unit pixel.

The present invention is applicable to various liquid crystal displays described above, however the TN-type active matrix liquid crystal display will be described as follows. Like shown above, a liquid crystal display element(it is called a liquid crystal panel) configuring the TN-type active matrix liquid crystal display(hereinafter, it is simply called an active matrix-type liquid crystal display) comprises: a gate line group arranged in to the 'x' direction on one transparent substrate to drive gate of switching element ; and a drain line group arranged in to the 'y' direction by being insulated with the gate line group to drive drain of switching element. Generally, TFT(Thin Film Transistor) is used for a representative switching element.

And, each area surrounded by the gate line and the drain line becomes a pixel area, respectively, and a transparent pixel electrode are formed on each pixel area.

The TFT is turned on by receiving a scanning signal in a gate line, and an image signal is supplied to the pixel electrode from the drain line.

The gate lines and drain lines are connected to TCPs(Tape Carrier Packages) having many driving ICs(Integrated Circuits). TCPs has image driving ICs and scanning driving ICs.However, because the TCPs having the driving ICs are installed outside of substrates, a display area formed by a crossed area of the gate line and the drain line of the substrates and an area(generally, it is called a frameborder) outside of the substrates gets bigger, therefore it violates a demand of reducing an external size of a liquid crystal display module unified with a liquid crystal display element, a backlight, and other optical elements.

Thus, to solve this problem, so-called flip-chip method or COG(Chip-On- Glass) method has been proposed((Japanese Laid Patent No. 95-256426). COG method directly mounts image driving ICs and scanning driving ICs on substrates itself without using TCP components to implement a high-density mounting effect of the liquid crystal display element as well as compactness. 5.

A method of attaching one pair of transparent substrates of a liquid crystal display in accordance with a prior art comprises alignment layers arranging liquid crystals in a first transparent substrate composed of a pixel electrode and a switching element and in a second transparent substrate composed of an electrode 0 opposite to the pixel electrode. And, a seal line and a liquid crystal injecting hole are formed outside of display areas of the first and the second transparent substrate, then a thermosetting or UN(Ultra Violet) setting epoxy is applied to the seal line area. To maintain the same cell gap in seal line area, the epoxy is mixed with a spacer, and the first transparent substrate is attached to the second transparent 5 substrate. After heating the epoxy with a UV lamp, hardening the epoxy completes this attachment, and a liquid crystal is injected to the cell gap through the liquid crystal injecting hole. An end seal is formed to complete the liquid crystal display.

In this case, since the epoxy is directly contacted with the liquid crystal, the 0 liquid crystal may be polluted to deteriorate a function of the display. Also, it is necessary to perform a process of deaerating an internal air bubble generated while mixing the epoxy with the spacer. As the epoxy spreads while attaching the transparent substrates, it causes many difficulties in cutting the transparent substrates. Moreover, the spacer used in the liquid crystal display uses many balls 5 having bigger diameters than the cell gap, therefore the outside of the balls composed of polymer chemicals is coated with a material with high conductivity such as silver, so as to apply electricity to the upper and the lower substrate.

However, it has difficulty in maintaining a uniform cell gap due to unequal diameters of the balls. The spacer optionally scattered during fabrication shades a light because a portion of the spacer exists in the display area of the liquid crystal display. In addition, there is a restriction on installing the display area to occupy many substrates as many as possible in the liquid crystal display.

DISCLOSURE OF INVENTION

To solve the above problems, it is an object of the present invention to provide a liquid crystal display having a conductive pillar for a stable distance by maintaining distance between an upper and a lower substrate and increasing electrical conductivity of the upper and the lower substrate, as well as controlling a liquid crystal injecting speed uniform.

It is another object of the present invention to provide a manufacturing method of liquid crystal display having a conductive pillar for a stable distance by maintaining distance between an upper and a lower substrate and increasing electrical conductivity of the upper and the lower substrate, as well as controlling a liquid crystal injecting speed.

To accomplish the above object, a liquid crystal display having a conductive pillar in accordance with the present invention, comprising: one pair of transparent substrates opposite to each other as maintaining a certain cell gap, and having a display area and a seal line; at least one pillar having same height as the cell gap in the seal line or having a higher height than the cell gap; a seal injected to the seal line formed outside of the display area; and a liquid crystal injected to the display area.

To accomplish the above another object, a method of fabricating a liquid crystal display having a conductive pillar in accordance with the present invention, comprising the steps of: forming at least more than one conductive pillar for applying electricity to one pair of transparent substrates in an upper part of at least one transparent substrate of the two transparent substrates; applying a seal for sealing transparent substrates to circumference of opposing sides of said transparent substrates except a liquid crystal injecting hole; attaching the two transparent substrates in an opposite direction; injecting a certain amount of liquid crystals to the conductive pillar between the transparent substrates and internal cells of the transparent substrates generated by the seal through the liquid crystal injecting hole; and sealing the liquid crystal injecting hole.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view illustrating one embodiment of a liquid crystal display having a conductive pillar in accordance with the present invention and a sectional view in A- A' direction.

FIG. 2 is a sectional view illustrating one pixel of a display area of a liquid crystal display having a conductive pillar in accordance with the present invention. FIG. 3 is a flow chart illustrating one embodiment of fabricating a liquid crystal display having a conductive pillar in accordance with the present invention.

BEST MODE FOR CARRING OUT THE INVENTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown.

FIG. 1 is a front view illustrating one embodiment of a liquid crystal display having a conductive pillar in accordance with the present invention and a sectional view in A- A' direction. Referring to FIG. 1(a) and 1(b), a liquid crystal display(lOO) is composed of a display area(20) formed in one pair of transparent substrates(10a, 10b) and a seal line(30) formed on an edge of the transparent substrates. A pixel electrode and a thin film transistbr(not shown), a switching element, are formed in the lower substrate(lθb) of the one pair of the transparent substrates, and an opposite electrode opposite to the pixel electrode is formed in the upper substrate(lθa).

Electronic field by formed a pixel electrode and an opposite electrode changes an arrangement of a liquid crystal injected between the one pair of transparent substrates(10a, 10b), thereby cutting off or transmitting light to display an image.

An electrode used in the display area(20) can be indium tin oxide, and a liquid crystal can be used with a TN(Twist Nematic) type. The seal line(30) is a area where a seal(35) for sealing the one pair of the transparent substrates is applied.

In the present invention, cylinder shape or other shape pillars are formed in the display area(20) and the seal line(30) in order to maintain a certain interval of a cell gap in the liquid crystal display. The reason for maintaining the certain interval of the cell gap is that it is necessary to keep a regular optical path by filling a liquid crystal in a pixel. The pillars(50) have conductive material like conductive polymer chemicals so that the upper substrate(lθa) and the lower substrate(lθb) can connected electronically. The height of the pillars(50) is the same as the cell gap or a little higher than the cell gap, completely adhering the pillars to the upper and the lower substrates. The seal line(30) is formed on an edge of the transparent substrates(10a, 10b), and have predescribed size interval to comprise a liquid crystal injecting hole(25) for injecting a liquid crystal. Generally, it is necessary to perform a process of deaerating air bubbles generated when the liquid crystal is not injected at regular speeds through the liquid crystal injecting hole(25). To prevent this process, a layer is formed in the liquid crystal injecting hole(25) to even an injecting speed of the liquid crystal, thereby preventing the air bubbles from being generated by speed difference of the liquid crystal.

However, this method further needs a process of forming the liquid crystal injecting hole after attaching the upper and the lower substrate. To omit this process, the pillars(50) for maintaining the cell gap are also made in a place where the liquid crystal injecting hole is formed, in order to prevent air bubbles while injecting the liquid crystal. The pillars(50) formed in the liquid crystal injecting hole(25) make possible to inject liquid crystal at regular speeds, prevent air bubbles and give many helps to easily seal liquid crystal injecting hole after injecting liquid crystal.

The pillars(50) can be formed by depositing conductive polymer chemicals on the transparent substrates(10a, 10b), and then using a photo-etching process with a photoresistor. The pillars(50) make the upper substrate(lθa) and the lower substrate(lθb) conductively. And, the cell gap of the one pair of the transparent substrates(10a, 10b) is uniformly maintained by using the pillars(50). The polymer chemicals can represent conductivity by doping a conductive material.

When a ball-shaped spacer is located in the display area to maintain the cell gap in a prior art, an adhesive material such as an epoxy is applied to the spacer, to fix a position of the spacer. In this case, when applying a voltage to the liquid crystal generates heat, degradation is generated in the epoxy to cause the liquid crystal to be polluted by the epoxy. A pollutant reduces resistivity of the liquid crystal as well as it reduces size of an electrical stress applied to both ends of the liquid crystal, giving an influence on capacity and reliability. The pillars(50) are formed in a step of fabricating the transparent substrates through a photo-etching process without an adhesive, thus preventing the liquid crystal from being polluted by degradation. The pillars(50) located in the display area(20) can be located on a cross point of intervals between pixels, and can correspond to each pixel of the liquid crystal display with a smaller number than the number of the pixels. Also, the pillars(50) can be formed in the seal line(30) only where a seal of an edge of the liquid crystal display(lOO) is applied. A diameter of the pillars located in the seal line can be bigger than that of pillars located in the display area when necessary. FIG. 2 is a sectional view illustrating one pixel of a display area of a liquid crystal display having a conductive pillar in accordance with the present invention. Referring to FIG. 2, a conductive pillar(50) is formed at regular intervals on a portion of a lower substrate(lθb) deposited with a thin film transistor(not shown) as a switching element. And, an upper substrate(lθa) deposited with an opposite electrode(13) is attached to an opposite part of the lower substrate.

The pixel electrode(l l) deposited on the lower substrate(lθb) is spaced with the conductive pillar(50), and the opposite electrode(13) deposited on the upper substrate(lθa) is contacted with the conductive pillar(50). Therefore, when a 7V voltage is applied to the pixel electrode(l 1) and a 2V voltage is applied to the conductive pillar(50) in order to turn on an pixel, the 2V voltage is applied to the opposite electrode(13) of the upper substrate(lθa), causing a 5V voltage difference between the opposite electrode(13) of the upper substrate(lθa) and the pixel electrode(l l) of the lower substrate(lθb). As a result, an electric field where the liquid crystal is driven is formed. At this time, one signal line of many signal lines incoming through a connector(not shown) for transmitting electrical signals to the liquid crystal display applies a regular voltage through the conductive pillar(50).

FIG. 3 is a flow chart illustrating one embodiment of fabricating a liquid crystal display having a conductive pillar in accordance with the present invention. Referring to FIG. 3, in a first step(ST 100), a liquid crystal display(lOO) comprises: rubbing orientation layer deposited on transparent substrates(10a, 10b) for specific alignment of the liquid crystal, and forming many pillars(50) at a predetermined position in the display area(20) and the seal area(30). The ρillars(50) are formed by depositing conductive polymer chemicals on the transparent substrates and using a photo-etching process with a photo mask, and particularly, the width of the pillars(50) can be minute by using a minute pattern mask. In addition, the pillars(50) can be formed outside of the transparent substrates(10a, 10b) by using an adhesive. The pillars(50) are also formed in a liquid crystal injecting hole. A rubbing process may proceed after forming the pillars(50).

In a second step(ST 110), a thermosetting or UV setting epoxy(70) is injected to the seal area(30).<At this time, since a cell gap is maintained by the pillars(50), it is unnecessary to inject a mixture of a spacer and the epoxy(70). Thus, it is possible to omit a process of deaerating air bubbles generated while mixing the epoxy(70) with the spacer.

At this time, the seal line, or seal area, prevents the UV setting epoxy(70) from being applied to a place where the liquid crystal injecting hole is formed.

In a third step(ST 120), the one pair of the transparent substrates(10a, 10b) are attached to each other oppositely after injecting the epoxy(70), and are heated by a UV lamp to harden the epoxy(70) for completion. At this time, when the epoxy is projected outside of the liquid crystal display(lOO), it is essential to carry out a process of cutting out the projected epoxy(70).

In a fourth step(ST 130), a liquid crystal(40) is injected between the transparent substrates(10a, 10b) through the liquid crystal injecting hole. Then, the liquid crystal injecting hole is sealed to complete the liquid crystal display(100).

As for the liquid crystal injection, the liquid crystal is injected to the display area(20) through the liquid crystal injecting hole by using difference of an external air. INDUSTRIAL APPLICABILITY

A liquid crystal display in accordance with the present invention comprises: a seal line for attaching an upper substrate and a lower substrate; and many pillars in display area and a liquid crystal injecting hole where a liquid crystal is injected. Therefore, it maintains a cell gap between the upper substrate and the lower substrate stably, and enables conductivity between the upper and the lower substrate by forming the pillars with conductive polymer chemicals. When injecting the liquid crystal to a display area after attaching the upper substrate and the lower substrate, the display area is decompressed to inject the liquid crystal through a process of injecting the liquid crystal by using a pressure difference with an exterior. While sealing a seal as controlling a liquid crystal injecting speed during injection, it prevents the seal from excessively permeating into the display area of the liquid crystal display through the liquid crystal injecting hole after releasing the decompressed display area.

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in different forms and should not be constructed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. A liquid crystal display having a conductive pillar, comprising: a pair of transparent substrates, installed opposite to each other as maintaining certain cell gap, and having a display area and a seal line; at least one conductive pillar having same height as said cell gap or higher than said cell gap in said seal line; a seal injected to said seal line formed outside of said display area; and a liquid crystal injected to said display area.

2. The liquid crystal display of claim 1, wherein at least one pillar is formed in said display area.

3. The liquid crystal display of claim 1, wherein said conductive pillar is formed in a liquid crystal injection hole.

4. The liquid crystal display of claim 2, wherein said conductive pillar is further in a liquid crystal injection hole.

5. The liquid crystal display of claim 1, wherein said conductive pillar is composed of polymer of high conductivity.

6. The liquid crystal display of claim 1, wherein said seal uses UV setting epoxy.

7. A method of fabricating a liquid crystal display having a conductive pillar, comprising steps of: forming at least one conductive pillar in an upper part of at least one of said transparent substrates for one pair of transparent substrates to be electrically connected with each other; applying a seal to circumference of opposing sides of said transparent substrates except a liquid crystal injection hole, said seal sealing said transparent substrates; attaching said one pair of the transparent substrates together by being opposite to each other; and injecting a certain amount of a liquid crystal into an internal cell of the transparent substrates through said liquid crystal injection hole, said internal cell comprised of said seal and said conductive pillar between said transparent substrates.

8. The method of claim 7, wherein said conductive pillar is formed in said liquid crystal injection hole, and said liquid crystal is injected at constant speed, thereby preventing air bubbles from being generated.

9. The method of claim 7, wherein polymer of high conductivity is deposited on at least one transparent substrate at said step of forming at least one conductive pillar, and a pillar is formed through photo-etching process.