TWI293133B - - Google Patents

Description

1293133 Amendment No. 5. Invention Description (1) <Scope of the Invention> The present invention relates to a fringe electric field switching type liquid crystal display (FFS-LCD), and more particularly to an FFS-[(3) using a positive-human | The layer to get the maximum transmittance. Inherent <Invention Background> In order to overcome the low viewing angle of the TN (Twisted Nematic) LCD, an In-Plane Switching (LPS) LC]) is recommended. , t is configured such that the upper and lower substrates are opposite each other by a predetermined distance. A liquid crystal layer including a plurality of liquid crystal molecules is interposed between the two substrates. Here, the halogen and the counter electrode containing the opaque material are formed on the lower substrate to drive the liquid crystal molecules, and the two electrodes are opened by the larger than the upper and lower doors to form a parallel electric field. Also, the pixel and the counter electrode are also; 2: width = maintain a constant electric field strength. Further, the parallel alignment layer is interposed between the upper and lower substrates and the liquid crystal layer. The &ー& ί /P^LCD has improved its viewing angle due to the parallel arrangement of liquid crystal molecules and the substrate. But hey, there are also shortcomings of low transmission.丨 # # is L to overcome the low transmittance problem of Ips-LCD, that is, the FIS_LCD is Ϊ 3 i LCD pixel and the opposite electrode is made of transparent conductor and electricity; the distance is less than the distance between the upper and lower substrates Edge 1 electricity % is formed on both electrodes. The conventional F f s _ l c D will be described in detail with reference to FIG. Figure 1 is a cross-sectional view of a conventional FFS-LCD. 14 γ ί makeup, 1 picture, the lower substrate 1 and the upper substrate 1 排列 are arranged to be opposite each other by a predetermined distance d (hereinafter referred to as early τ gap). Further, a liquid crystal layer 15 is interposed between the substrate 1 and the upper substrate 10. Liquid Page 8 1293133 _ Case No. 90115535_年月日日_i±±_ V. DESCRIPTION OF THE INVENTION (2) The crystal layer 15 includes a plurality of liquid crystal molecules having positive or negative dielectric anisotropy. The retardation value of the result of multiplying the cell gap d by the refractive anisotropy ζ] η is preferably at 0.25 to 0·35" m to obtain the maximum transmittance. Although not shown in the drawings, a gate busbar and a data busbar intersect the lower substrate 1 to define a unit cell and a thin film transistor (not shown) and are disposed at the intersection of the two lines. Further, the pair of electrodes 3 are formed in the unit pixel of the lower substrate 1. The counter electrode 3 includes a transparent ITO (Indium Tin 0 x i d e ) layer and has a shape of a crucible or a plate. A gate insulating layer 4 is formed in a meandering shape on the top portion of the counter electrode 3 to overlap the counter electrode 3. The distance between the counter electrode 3 and the pixel electrode 5 is narrower than the cell gap d. Further, a horizontal alignment layer 6 is formed on the surface of the lower substrate 1 to complete the arrangement of the liquid crystal molecules at the beginning. The horizontal alignment layer 6 has a friction axis and a predetermined pretilt angle in a predetermined direction. On the other hand, a color filter 12 is formed on the upper substrate 10 and opposed to the lower substrate 1. A horizontal alignment layer 14 is also formed on the surface of the color filter 12 to control the configuration of the liquid crystal molecules at the beginning. The horizontal alignment layer 14 also has a predetermined pretilt angle and a friction axis which forms an angle of 180° with the lower substrate. The conventional F F S - L C D acts as follows. First, when a voltage difference is generated between the counter electrode 3 and the pixel electrode 5, that is, since the distance between the counter electrode 3 and the pixel electrode 5 is smaller than the cell gap d, a fringe electric field is formed between the electrodes. The fringe electric field affects the upper portion of the counter electrode 3 and the upper portion of the halogen electrode 5. This is because the opening space of the counter electrode 3 between the pixel electrodes 5 is narrow, so that most of the liquid crystal molecules in the unit pixel can be driven. As a result, both the transmittance and the aperture ratio are improved.

1293133 _ Case No. 90115535_年月日日__ V. Description of Invention (3) Generally, conventional FFS-LCDs use two kinds of liquid crystals, positive and negative dielectric anisotropy, as liquid crystal layers. However, the response rate is faster, and negative dielectric anisotropic liquid crystals are more popular. When a liquid crystal having a negative dielectric anisotropy is used, the retardation value determines the maximum transmittance, and when a liquid crystal layer using positive dielectric anisotropy is used as the liquid crystal layer, it is difficult to obtain the retardation condition. Maximum transmission rate. <General Theory of Invention>

Accordingly, the present invention has been made in view of the above conventional technical problems. It is an object of the present invention to provide an FFS-LCD which can use a positive dielectric anisotropic liquid crystal to obtain a maximum transmittance. In order to achieve the above object, the present invention comprises: an upper and lower substrate opposite to each other at a predetermined distance; a liquid crystal layer interposed between the two substrates, comprising liquid crystal molecules having positive dielectric anisotropy, and retardation of the liquid crystal layer thereof a transparent counter electrode formed on the inner surface of the lower substrate; a transparent pixel electrode disposed on the inner surface of the lower substrate, forming a fringe electric field with the counter electrode Driving liquid crystal molecules; and a horizontal alignment layer interposed between the upper and lower substrates and the liquid crystal layer, respectively, having a predetermined friction axis. <Detailed Description of Preferred Embodiment>

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described in detail with reference to the drawings. 2 and 3 are cross-sectional views of the FFS-LCD of the present invention, and FIG. 4 is a graph showing the transmittance as a function of the retardation, including a conventional FFS-LCD, a TN-LCD, and the FFS-LCD of the present invention, using positive A dielectric anisotropic liquid crystal layer. Referring to Figures 2 and 3, the FFS-LCD of the present invention includes a lower substrate 20 and an upper substrate 40 opposed to each other by a predetermined distance d (hereinafter referred to as a cell gap).

Page 10 1293133 _ Case No. 90115535_ Year j θ ί more positive ____ V. Description of the invention (4) The d value in the embodiment is 2 to 6 μ m. Further, a liquid crystal layer 30 is interposed between the upper and lower substrates 40 and 20, and includes a plurality of liquid crystal molecules 30 a having a positive dielectric anisotropy value of 4 to 15. Although not shown in the drawings, the gate/data busbar is placed on the lower substrate 20 to define a unit pixel. Further, a thin film transistor (not shown) is disposed at the intersection of the two lines. In the unit pixel of the lower substrate 20, the pair of electrodes 2 2 are formed in a meandering or plate shape, and contain a transparent conductive I T 0 layer. In the embodiment, the counter electrode 22 is formed into a plate shape. Further, a gate insulating layer 24 is formed on the lower substrate 20 of the counter electrode 2 2 . Further, a unitary electrode 26 is formed on the gate insulating layer 24 in a meandering shape and overlaps the counter electrode 22. The distance 1 between the counter electrode 2 2 and the pixel electrode 26 is smaller than a cell gap d, whereby a fringing electric field is formed between the electrodes 2 2 and 2 6 . In addition, a first horizontal alignment layer 28 is formed on the surface of the completed lower substrate 20 for controlling the initial alignment of liquid crystal molecules. In order to obtain the maximum transmittance, the first horizontal alignment layer 28 has a friction axis which forms 45 to 90, preferably 60 to 85, between the projection lines of the upper edge electric field of the substrate. In the corner, this side field is formed between the counter electrode 2 2 and the pixel electrode 26. On the other hand, a color filter 42 is formed on the reverse side of the upper substrate 40 corresponding to the lower substrate 20. A second horizontal alignment layer 44 is formed on the surface of the color transition unit 4 2, and has a friction axis which forms a predetermined angle with the friction axis of the first horizontal alignment layer 28, for example, 1 80°, and a polarizing plate 4 5 a is attached to the outer surface of the lower substrate 2 线性 for linear polarization of light from a backlight (not shown), and a beam splitter 45b

Page 11 1293133 _ Case No. 90115535 V. Description of the Invention (5) 3 de The decomposer is attached to the outer surface of the upper substrate 40 for selectively absorbing and transmitting light passing through the liquid crystal layer 30. Here, the polarization axis (not shown) of the polarizing plate 45a is parallel to the friction axis of the first horizontal alignment layer 28, and the absorption axis (not shown) of the beam splitter 45b is perpendicular to the polarization axis. According to the FFS-LCD of the present invention, the operation is as follows: First, as shown in Figs. 2 and 3, when an electric field is not formed between the counter electrode 2 2 and the halogen electrode 26, the positive dielectric anisotropic liquid crystal molecule The 〇a series are arranged such that their major axes are parallel to the friction axes of the first and second horizontal alignment layers 28 and 44. The direction of advancement of the light is not changed as it passes through the liquid crystal layer 30, since the spindle is parallel to the friction axis. After passing through the liquid crystal layer 30, the light is absorbed by the beam splitter 4 5 b having an absorption axis perpendicular to the polarization axis, so that the screen is dark. On the other hand, when a potential difference is generated between the counter electrode 2 2 and the pixel electrode 26, a fringe electric field F is formed. Then, the positive dielectric anisotropic liquid crystal molecules 30 a are aligned and whose principal axis is parallel to the fringe electric field F. Therefore, the light changes due to the polarized light when passing through the liquid crystal layer 30. Thereby, the light is not absorbed by the beam splitter 45b, and as a result, the screen is white. In a conventional LCD, liquid crystal molecules on the surface of the alignment layer are arranged in accordance with the alignment layer due to the anchoring force of the alignment layer or the formation of an electric field. However, in the FFS-LCD, since the distance between the counter electrode 22 and the pixel electrode 26 is narrow, a strong electric field is generated between the electrodes, particularly on the surface of the first horizontal alignment layer 28. In addition, the positive dielectric anisotropic liquid crystal molecules are twisted into flat due to their major axes.

Page 12 1293133 Case No. 90115535 V. Invention Description (6) Acting on the electric field, it is more powerfully driven. Therefore, when the FFS-LCD uses a positive dielectric anisotropic liquid crystal layer, ϊ Γ: after the field, even in the first The liquid crystal bifurcation on a horizontal alignment |28 is distorted parallel to the electric field. υ 8 also results in different transmittances even when the positive and negative dielectrics are the same in retardation. 11 ’ ' ' a aa layer of push;, the first, \ map shows the transmittance as a function of the degree of delay. More specifically, A透过 is a case where the transmittance curve which varies with the retardation in the conventional FFS_LCD is in the case of the TN-LCD, and σ is the case when the electric anisotropic liquid crystal layer is made in ffs lcd. In the figure 4, the traditional FFS-LCD has a maximum transmittance of 〇·2 to 〇·3, while the TN-LCD has a delay of 〇·4 to 〇^. The τ page attack uses positive dielectric. In the FFS_LCD of an anisotropic liquid crystal layer, the maximum transmittance can be obtained at a degree of 〇.3 to 〇·45//m, which is the curve of the late transition TN-LCD. The reason is that the FFS-LCD uses the positive media. When the liquid crystal layers are electrically entangled, the liquid crystal molecules on the first alignment layer 28 can be driven. As in the above case, in the FFS-LCD using the positive dielectric anisotropic crystal layer in accordance with the present invention' The maximum transmittance can be obtained when the degree of delay is 〇·3 to 45·45//m. The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. The equivalent changes and modifications made by the scope of the patent application of the present invention are all covered by the scope of the invention.

Page 13 1293133 _ Case No. 90115535_年月日日__ BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of a conventional FFS-LCD; Figures 2 and 3 are cross-sectional views of the FFS-LCD of the present invention; A graph showing a transmittance according to a conventional FFS-LCD, a TN-LCD, and an FFS-LCD of the present invention as a function of the retardation, and a liquid crystal layer of positive dielectric anisotropy is used. <Component Name and Symbol Comparison Table> 20: Lower substrate 3 0 a · Liquid crystal molecule 22 Counter electrode 24 Gate insulating film 26 Pixel electrode 28 First horizontal alignment layer 30 Liquid crystal layer 40 Upper substrate 42 Color filter 4 5 a : polarizing plate 4 5 b : beam splitter 44 : : second horizontal alignment layer

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Claims (1)

Tiger 90115535 Λ_a 1. A fringe field switched liquid crystal display (FFS-LCD) comprising an upper and a lower substrate opposite each other at a predetermined distance; a liquid crystal layer interposed between the two substrates, comprising positive dielectric An anisotropic liquid crystal molecule having a retardation of 0.3 to 0.5 Å; a counter electrode formed on an inner surface of the lower substrate; a halogen formed on an inner surface of the lower substrate And an electrode forming a fringe electric field to drive the liquid crystal molecules with the counter electrode; and a horizontal alignment layer between the upper portion and the lower substrate and the liquid crystal layer, having a predetermined friction axis. 2. The edge electric field switching liquid crystal display (FFS-LCD) of claim 1, wherein the liquid crystal molecule has a dielectric anisotropy ratio of 4 to 15 〇 3. As claimed in the first aspect of the patent scope An electric field switching liquid crystal display (FFS-LCD), wherein a distance between the upper and lower substrates is 2 to 6 β m 〇 4. The edge electric field switching liquid crystal display (FFS-LCD) as claimed in claim 2 The distance between the upper and lower substrates is 2 to 6/zm 〇 5. The edge electric field switching liquid crystal display (FFS-LCD) of claim 1, wherein one of the horizontal alignment layers The friction axis and the projection line formed between the opposite electrode and the pixel electrode have an angle of 45° to 90° on the projection line on the substrate. 6. For example, the edge electric field switching liquid crystal display of the fifth application patent scope Page 15 1293133 _ Case No. 90115535_Yearly Revision _6. Patent Application Ranger (FFS-LCD), wherein the friction axis of the other horizontal alignment layer and the opposite electrode and the pixel electrode are formed The projection line of the fringe electric field on the substrate is at an angle of 60° to 80°. 7. The edge electric field switched liquid crystal display (F F S - L C D) of claim 5, wherein the friction axis of the other horizontal alignment layer forms an angle of 180° with the friction axis of a horizontal alignment layer. 8. The edge electric field switching type liquid crystal display (FFS-LCD) of claim 1, wherein the counter electrode forms a plate shape and the halogen electrode forms a meander shape. 9. The edge electric field switching liquid crystal display (FFS-LCD) of claim 1, wherein the counter electrode and the pixel electrode are both formed in a meander shape. 10. The edge electric field switching liquid crystal display (FFS-LCD) of claim 1, wherein the distance between the opposite and the pixel electrodes is smaller than the distance between the upper and lower substrates. 1 1. A fringe field switched liquid crystal display (FFS-LCD) according to claim 1, wherein at least one of the pair of electrodes and the pixel electrode is made of an opaque substance. 1 2 . The edge electric field switching liquid crystal display (FFS-LCD) of claim 1, wherein at least one of the pair of electrodes and the pixel electrode is made of a transparent material. The edge electric field switching type liquid crystal display (FFS-LCD) of claim 12, wherein the opposite and the halogen electrodes are made of a transparent substance. Page 16