KR20060066284A - Liquid crystal display - Google Patents

Abstract

The present invention relates to an optically compensated band mode liquid crystal display device, and the present invention uses an inorganic alignment layer having a good alignment property capable of forming a pretilt angle such that the liquid crystal molecules initially have a band alignment close to that of the OCB mode. Liquid crystal molecules can be driven without transition from splay orientation to band orientation, thereby reducing the low voltage driving and driving time, and having an OCB mode that can move quickly from band orientation to twist orientation, vertical orientation, etc. Provided is a liquid crystal display device.

LCD, OCB, band transition, inorganic alignment film

Description

Liquid crystal display

1 is a cross-sectional view of an OCB mode liquid crystal display device according to the present invention;

2A to 2C are cross-sectional views illustrating the operation of the OCB mode liquid crystal display device according to the present invention.

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal layer of a liquid crystal display device.

Twisted nematic (TN) mode liquid crystal displays have been widely used in displays such as notebook computers, despite their narrow viewing angles. However, improving the viewing angle is an essential prerequisite for liquid crystal displays to replace cathode ray tube (CRT) displays in the monitor and television markets.

Accordingly, recently, an optically compensated band (hereinafter referred to as OCB) mode liquid crystal display device that compensates refractive index anisotropy of liquid crystal molecules to improve response speed while obtaining even viewing angle characteristics in all directions is proposed. It became.

The OCB liquid crystal display device includes an electrode for driving liquid crystal molecules of the liquid crystal layer on each inner surface of the upper and lower substrates, and an alignment layer for the alignment of liquid crystal molecules, respectively, between the upper and lower substrates disposed opposite to each other. And a polarizing plate having a predetermined polarization axis on each of the outer surfaces of the substrates, wherein a predetermined high voltage is applied to the initial splay oriented liquid crystal molecules so that the arrangement of the liquid crystal molecules is in a bend orientation. After the transition, the magnitude of the voltage is changed to adjust the degree of bending of the band, thereby controlling the light transmittance to display an image.

 However, since the OCB liquid crystal display has a structure in which the liquid crystal molecules must be shifted from the splay orientation to the band orientation as described above, a high driving voltage is required to achieve this, so that the power consumption rise is a problem. do. In addition, since it is obvious that the response speed becomes longer when the alignment transition of the liquid crystal molecules is essentially performed as described above, it is expected that the reliability of the product of the liquid crystal display device is lowered at this time.

This problem is that when the horizontal alignment layer provided for the liquid crystal alignment is formed of an organic alignment layer, it has a pretilt angle limited to about 12 degrees, and the vertical alignment layer also has a limitation in adjusting the pretilt angle of the organic vertical alignment agent. Because.

Accordingly, the present invention is to solve such a conventional problem, and an object of the present invention is to artificially adjust the pretilt angle using an inorganic alignment layer to obtain a desired pretilt angle so that liquid crystal molecules do not undergo a transition from splay alignment to band alignment. It is to provide a liquid crystal display device that can be driven.

It is also an object of the present invention to provide a field sequential drive type liquid crystal display device which responds quickly at low voltage suitable for moving image display using such a liquid crystal display device.

MEANS TO SOLVE THE PROBLEM In order to solve the subject of this invention, the present invention provides the 1st board | substrate and the 2nd board | substrate which are mutually arrange | positioned at intervals, the 1st alignment film formed in the 1st surface of the said 1st board | substrate, and the 1st surface of the said 1st board And a second alignment layer formed on one surface of the second substrate facing each other, and a liquid crystal blue layer composed of several liquid crystal molecules interposed between the first alignment layer and the second alignment layer, wherein each of the alignment layers is 80 to 90 degrees. Or a liquid crystal display device having a pretilt angle composed of 80 to 85 degrees.

The first and second alignment layers of the liquid crystal display are inorganic alignment layers, and the liquid crystal layer is disposed perpendicular to the first and second alignment layers at the center of the intermediate line between the first and second alignment layers. The closer to the first and second alignment layers, the smaller the inclination angle with respect to the first and second alignment layers.

In the liquid crystal layer, the upper liquid crystal layer and the lower liquid crystal layer are symmetric about the intermediate line between the first and second alignment layers, that is, the upper liquid crystal layer is twisted 90 degrees clockwise about the middle line between the first and second alignment layers. The lower liquid crystal layer may be configured to be twisted 90 degrees in the counterclockwise direction. The first and second alignment layers may have the same pretilt angle, and the inorganic alignment layer may be formed by sputtering any one of SiC, SiO ₂ , Al ₂ O ₃ , CeO ₂ , SnO ₂ , ZnTiO ₂ , InTiO ₂ , and DLC. do.

The liquid crystal display according to the present invention may be applied to a liquid crystal display driven in a field sequential manner.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. These embodiments of the present invention are merely for illustrating the present invention, but the present invention is not limited thereto.

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

First, referring to FIG. 1, the lower substrate 21 and the upper substrate 31 are disposed to face each other at a predetermined distance. The driving electrode, for example, the pixel electrode 23 is formed on the inner surface of the lower substrate 31, and the first alignment layer 25 is formed on one surface of the pixel electrode 23. The driving electrode, for example, the common electrode 33 is formed on the inner surface of the upper substrate 31, and the second alignment layer 35 is formed on the surface of the common electrode. The pixel electrode 23 and the common electrode 33 may be formed of a transparent conductor in the case of a transmissive type, and the pixel electrode 23 may be formed of an opaque conductor in a case of a reflective type.

The first polarizing plate 29 having a predetermined polarization axis (first polarization axis) is disposed on the outer surface of the lower substrate 21. In addition, a second polarizing plate 39 having a predetermined polarization axis (second polarization axis) is disposed on the outer surface of the upper substrate 31. Wherein the first and second polarization axes are arranged to intersect with each other and any one of these polarization axes is at an angle with the rubbing axis, for example from 25 degrees to 50 degrees or from 110 degrees to 140 degrees, more preferably 45 degrees or 135 degrees. It is preferred to be arranged to form a figure.

The liquid crystal layer 40 including the plurality of liquid crystal molecules 40a is interposed in the space between the lower substrate 21 and the upper substrate 31. The liquid crystal molecules 40a in the liquid crystal layer 40 may have positive dielectric anisotropy. In the liquid crystal layer 40, the first and second alignment layers 25 and 35 include SiC, SiO ₂ , Al ₂ O ₃ , CeO ₂ , SnO ₂ , ZnTiO ₂ , InTiO ₂ , and diamond like carbon (DLC). Since the inorganic alignment film formed by sputtering any one of inorganic materials can have a pretilt angle of 80 to 90 degrees, the alignment of the OCB mode band can be achieved. In the present embodiment, the alignment layers 25 and 35 have a pretilt angle of 80 to 85 degrees.

Accordingly, the liquid crystal molecules are oriented by the stretching direction due to van der Waals forces between the first and second alignment layers 25 and 35 and the liquid crystal molecules 40a, and the liquid crystal molecules are excluded from the liquid crystal alignment layer by the exclusion volume effect. Is arranged to be the minimum, that is, the liquid crystal molecules 40a are disposed perpendicular to the first and second alignment layers 25 and 35 at the center about the intermediate line ML and the first and second alignment layers Closer to (25, 35) is configured to reduce the angle with respect to the first and second alignment layer (25, 35)

In order to make the liquid crystal molecules of the liquid crystal layer exhibit band alignment by using the inorganic alignment layer according to the present invention, in the present embodiment, when the ion beam incident angle for sputtering is 50 degrees, a pretilt angle of 80 degrees is used, and when the 55 degrees is 85 degrees, When the pretilt angle is 60 degrees, an ion beam sputter deposition apparatus having a pretilt angle of 90 degrees is used. According to this apparatus, any one of inorganic materials such as metals, oxides, and fluorides, such as SiC, SiO ₂ , Al ₂ O ₃ , CeO ₂ , SnO ₂ , ZnTiO ₂ , InTiO ₂ , or DLC, can be used for ion beam sputter When the deposition is performed while controlling the ion beam deposition angle or the like using the deposition apparatus, an alignment film having a pretilt angle of 80 to 90 degrees can be formed. Further, while the substrate is rotated in-plane, a wider pretilt angle can also be formed by repeatedly carrying out an all-round deposition method from all directions.

Hereinafter, the operation and effects of the OCB mode liquid crystal display according to the present invention will be described with reference to FIGS. 2A to 2C.

2A to 2C are cross-sectional views illustrating the operation of the OCB mode liquid crystal display device according to the present invention.

First, as shown in FIG. 2A, when no low voltage difference is generated between the pixel electrode and the common electrodes 23 and 33, the liquid crystal molecules 40a affect only the first and second alignment layers 25 and 35. It is arranged in the form of a band or similar.

Then, when a voltage Vs of 5 V is applied, as shown in FIG. 2C through the stable band state of FIG. 2B, the liquid crystal molecules 40a in the intermediate line ML are formed by the electric field and its molecular axis. The liquid crystal molecules 40a in a band state are also aligned perpendicular to the first and second alignment layers 25 and 35.

At this time. Unlike conventional liquid crystal displays, the OCB mode liquid crystal display exhibits a maximum amount of light in a state in which voltage is applied to the pixel electrode, and when the liquid crystal molecules are arranged in a vertical state, a white (or dark) state or a minimum amount of light is displayed. To dark (or white).

In the OCB mode liquid crystal display, since the liquid crystal molecules 40a are arranged up and down symmetrically with respect to the intermediate line when the electric field is formed, the phase is shifted while the light passes through the upper substrate 31 from the lower substrate 21. It is naturally compensated. In addition, since the dark state (white state), that is, the vertical state is achieved without requiring a predetermined threshold voltage, no back-flow phenomenon occurs and it has a relatively fast response speed.

According to several experiments by the inventors of the present invention, unlike the case of using an organic alignment layer in which the transition time to the conventional band state took 300 milliseconds (msec) or more at room temperature, the OCB mode according to the present invention is in the on state. Fast transition from band to vertical is 10 milliseconds (msec), generally no transition from slower splay to band state, fast transition from off to vertical to band, The transition to the splay state does not appear in the slower band.

In addition, in the case of the organic alignment layer which requires a transition voltage to a conventional band state, a voltage of 20 V or more is required, but in the OCB mode according to the present invention, since the transition from the spray state requiring the voltage above the threshold voltage to the band state does not occur, It can be driven at low low pressure, such as 5V.

In addition, when the OCB mode is applied to a field sequential liquid crystal display device, it is possible to design in a cell gap of 5 to 6 µm, and in the liquid crystal panel of the OCB mode, the liquid crystal alignment is changed from a band state for spraying an image to a spray state. Since no inverted state occurs, it is not necessary to apply high voltage compared to OCB type liquid crystal display device that applies high voltage for initial liquid crystal alignment. Therefore, low voltage driving is possible, response speed is high, and color clarity is high. The color unevenness is extremely small and the color separation is easy, so it can have various effects.

In the above description of the preferred embodiment of the present invention in detail, but the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concept of the present invention defined in the following claims are also present invention It belongs to the scope of rights.

As described above, according to the present invention, there is provided a liquid crystal display having an OCB mode in which liquid crystal molecules can quickly move from band orientation to twist orientation, vertical alignment, and the like at low voltage without undergoing a transition from splay alignment to band alignment. can do.

In addition, the liquid crystal alignment is good, it is possible to provide a liquid crystal display device having an alignment film in which the pretilt angle of the liquid crystal molecules follows the band alignment of the OCE mode.

In addition, the present invention can significantly reduce the voltage and time for the band transition in the splay band when using the OCB mode for video display using the inorganic alignment layer, and can produce a highly reliable display with excellent light stability and thermal stability .

Claims (17)

A first substrate and a second substrate disposed to face each other with a gap therebetween; A first alignment layer formed on one surface of the first substrate; A second alignment layer formed on one surface of the second substrate facing one surface of the first substrate; And, A liquid crystal blue layer composed of several liquid crystal molecules interposed between these first alignment films and the second alignment films, Wherein each of the alignment layers has a pretilt angle of 80 to 90 degrees. The method of claim 1, The liquid crystal layer is disposed perpendicularly to the first and second alignment layers at the center of the intermediate line between the first and second alignment layers, and closer to the first and second alignment layers, so that the liquid crystal layer is formed on the first and second alignment layers. Liquid crystal display device that the inclination angle is reduced. The method of claim 2, The liquid crystal layer is divided into an upper liquid crystal layer and a lower liquid crystal layer around an intermediate line between the first and second alignment layers, and the liquid crystal molecules of the upper liquid crystal layer and the liquid crystal molecules of the lower liquid crystal layer are arranged in a symmetrical state. Liquid crystal display. The method of claim 3, And the upper liquid crystal layer is twisted 90 degrees clockwise and the lower liquid crystal layer is twisted 90 degrees counterclockwise around the intermediate line between the first and second alignment layers. The method of claim 1, The first and second alignment layers have the same pretilt angle. The method of claim 1, The first and second alignment layers have a pretilt angle of 80 degrees to 85 degrees. The method of claim 1, And the first and second alignment layers are inorganic alignment layers. The method of claim 7, wherein The inorganic alignment layer is formed by sputtering any one of SiC, SiO ₂ , Al ₂ O ₃ , CeO ₂ , SnO ₂ , ZnTiO ₂ , InTiO ₂ , and DLC. The method of claim 1, The liquid crystal display device is an OCB mode liquid crystal display device driven in a field sequential manner. A liquid crystal display panel displaying an image, and In the field-sequential liquid crystal display device comprising a light source for supplying light to the liquid crystal display panel, wherein the light source is time-divided and emitted light, The liquid crystal display panel, A first substrate and a second substrate disposed to face each other with a gap therebetween; A first alignment layer formed on one surface of the first substrate; A second alignment layer formed on one surface of the second substrate facing one surface of the first substrate; A liquid crystal layer interposed between these first alignment films and the second alignment films, Each of the alignment layers may be an inorganic material. The method of claim 10, And the first and second alignment layers have a pretilt angle consisting of 80 degrees to 90 degrees. The method of claim 11, And the first and second alignment layers have a pretilt angle of 80 degrees to 85 degrees. The method of claim 10, The liquid crystal layer may be disposed perpendicular to the first and second alignment layers at the center of the intermediate line between the first and second alignment layers, and closer to the first and second alignment layers. Field sequential liquid crystal display device with an angle reduced. The method of claim 13, The liquid crystal layer is a field sequential mode liquid crystal display device in which the upper liquid crystal layer and the lower liquid crystal layer are symmetric about an intermediate line between the first and second alignment layers. The method of claim 13, And the upper liquid crystal layer is twisted 90 degrees clockwise and the lower liquid crystal layer is twisted 90 degrees counterclockwise around the intermediate line between the first and second alignment layers. The method of claim 12, And the first and second alignment layers have the same pretilt angle. The method of claim 10, The inorganic alignment layer is formed by sputtering any one of SiC, SiO ₂ , Al ₂ O ₃ , CeO ₂ , SnO ₂ , ZnTiO ₂ , InTiO ₂ , and DLC.

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