KR102105573B1 - wide viewing angle and ultra high definition liquid crystal display - Google Patents

Abstract

A liquid crystal display device comprising a lower substrate on which a first polarizing plate is installed, an upper substrate on which a second polarizing plate is installed, a liquid crystal positioned between them, a thin film transistor installed on the lower substrate, and a gate line, data line, and pixel electrode connected thereto. In each of the pixel regions, a first common electrode that forms a through hole with an insulating layer therebetween over a planar pixel electrode on a lower substrate and a second common electrode that is operated with the same polarity as a common electrode on the upper substrate are provided with light. When a voltage is applied, the liquid crystal array around the fringe of the through hole is shifted from vertical or horizontal to an inclined state to pass light, and the through hole is applied with a transmissive voltage in a single pixel or across the same color pixels adjacent to each other by the installation direction of the fringe Characterized in that it is formed so that the liquid crystal is inclined in at least three different normal directions. The liquid crystal display device is disclosed.
According to the present invention, the response speed of the liquid crystal display device can be increased to drive a high-speed 120Hz refresh rate in an ultra-high resolution liquid crystal panel, and a manufacturing process or a liquid crystal display device is constructed by using a feature structure of a through hole of a common electrode of an FFS type liquid crystal display device. And it is possible to easily achieve the pixel division by the liquid crystal inclination direction without making the driving method complicated or unreasonable, thereby improving the viewing angle characteristics of the liquid crystal display device.

Description

Wide viewing angle and ultra high definition liquid crystal display

The present invention relates to an active-driven liquid crystal display device, and more particularly, to a super-high-definition liquid crystal display device suitable for super-integrating pixels and fast driving.

The liquid crystal switching method is largely divided into a twisted nematic (TN) method, an in-plane switching (IPS) method, a vertical alignment (VA) method, and a fringe field switching (FFS) method, depending on the existing alignment and voltage-driven switching operation. Can be.

The pixel structure of the LCD also differs depending on the driving method. In the pixels of the TN- and VA-type LCDs, a pixel electrode is formed on one side of a pair of substrates, a common electrode is formed on the other side, and liquid crystal molecules are formed by forming a vertical electric field on two substrate surfaces between the pixel electrode and the common electrode. By controlling the orientation of, the transmittance of the pixel is controlled.

In the FFS method, a pixel electrode and a common electrode are formed to face each other with an insulating film interposed within the lower substrate. In the FFS method, the common electrode is usually installed in a plane at the bottom, and the pixel electrode is formed in parallel with a plurality of patterns with slits, and the arrangement of liquid crystal molecules is substrate by an electric field (fringe field) formed between the pixel electrode and the common electrode. Since it is controlled almost in parallel, the FFS mode LCD has a wide viewing angle and a transparent electrode, which has a higher transmittance than IPS.

However, one of the biggest limitations in the liquid crystal display device is related to a video or game display in which an image can change very quickly. A liquid crystal display device has been developed for various purposes, and in the case of a head mounted display (hereinafter referred to as 'HMD') for spherical virtual reality, it is also being developed as a display device with organic EL. A liquid crystal panel used as an HMD display device requires a resolution of at least 4K, generally 8K, to feel like a reality. In addition, the unit pixel pitch must be 8 micrometers or less in order to realize a high resolution of 1000 ppi or more on a 3 inch or less display such as an HMD.

Compared with other display devices such as CRTs and OLEDs, as shown in Equations 1 and 2 below, a response speed is slow due to characteristics such as inherent viscosity and elasticity of the liquid crystal.

The response speed of the LCD is 100% of the light transmittance after passing through the input polarizer, the liquid crystal cell (Cell), and the output polarizer in normal white light, and the transmittance is between 10% and 90% when the screen becomes dark and bright. It refers to the sum of the changing time. The time taken when changing from 10% to 90% is called Rising Time, and the time taken when changing from 90% to 10% is called Falling Time. White to Black) It is called response speed or response time.

(Equation 1)

Here, τ _r is the rising time when the voltage is applied to the liquid crystal, Va is the applied voltage, and VF is the Freederick Transition Voltage at which the liquid crystal molecules start to respond to the voltage, d denotes the cell gap of the liquid crystal cell, and γ (gamma) denotes the rotational viscosity of the liquid crystal molecule.

(Equation 2)

Here, τ _f denotes a falling time in which the liquid crystal is restored to its original position by the elastic restoring force after the voltage applied to the liquid crystal is off, and K denotes the elastic modulus inherent to the liquid crystal, respectively.

That is, in the liquid crystal display device, the response speed τ _f is greatly affected by the rotation viscosity and elastic modulus, which are characteristics of the liquid crystal itself, and it is urgently requested to solve the problem of the response speed in order to be adopted as a display in the HMD.

The field sequential full-color display method, which requires no color filter, is characterized by using a backlight that turns on sequentially from "red to green to blue." In a typical CRT or liquid crystal display, the frame time is 16.7 ms. , In the field sequential full color display method, the frame time is 5.6 ms, and high-speed response is required.

As an index indicating high-speed responsiveness, the sum of τ _f and τ _{r seen} above can be mentioned. τ _f is the falling response time of the liquid crystal, and τ _r is the rising response time of the liquid crystal. In order to satisfy high-speed responsiveness in the field sequential full-color display method, it is desired that τ _f and τ _r are less than 1.5 ms each.

It is known that the response time or response speed of the liquid crystal should be 4 ms or less in order to realize a high-definition screen of a high-speed game with a frame rate of 120 Hz while reducing the afterimage effect as much as possible even in a normal color filter LCD. As a display device, it was difficult to achieve such a drive of about 120hz on such an ultra-high definition high resolution screen.

As can be seen from the fact that the liquid crystal of the liquid crystal display device has an elastic modulus, the behavior of the elastic body is large. Usually, the larger the elastic modulus is, the higher the response speed is, so that the switching deformation of the liquid crystal in the liquid crystal driving is a deformation having a large elastic modulus. It becomes important.

However, the elastic deformation of the liquid crystal does not consist of one type, and can be divided into a splay type, a twist type, and a band type elastic deformation. Among these, the band type elastic deformation has the largest value, and the band type elastic deformation is applied to driving the liquid crystal. Using and restoring can reduce the response time of the liquid crystal and increase the number of driving frames.

On the other hand, even if the viewing angle and transmittance characteristics of the liquid crystal display device are good, the problems of the viewing angle and transmittance still exist according to the properties of the liquid crystal of all liquid crystal display devices and the fundamental characteristics of liquid crystal alignment, and efforts to improve it are necessary. Do.

Known techniques for improving the viewing angle characteristic or widening the viewing angle of a liquid crystal display device include a method of moving liquid crystal molecules in a direction almost parallel to a substrate surface and a method of moving a liquid crystal pixel when liquid crystal molecules move in a direction perpendicular to the substrate surface. And a method in which a molecule is divided into a plurality of regions having different orientations.

A representative display method using the former technology is an IPS (In-Plane Switching) method. The representative display method using the latter technique is a wide viewing angle liquid crystal display method in which the axially symmetrical horizontal alignment of the Pnlc (Positive Nematic Liquid crystal) liquid crystal material (Japanese Patent Publication No. 7-120728), vertically oriented Pnlc (Positive Nematic Liquid) A crystal-type liquid crystal material is divided into regions to control the applied electric field, so that a wide viewing angle liquid crystal display system (Japanese Patent Laid-Open Publication No. 7-28068) and Pnlc (Positive Nematic Liquid crystal) for each pixel The liquid crystal material includes a wide viewing angle liquid crystal display method (AM-LCD'96, page 185, 1996) in which the liquid crystal material is horizontally oriented differently in each region by dividing the liquid crystal material into four regions.

In the liquid crystal display device (WO 2014042425 A1) disclosed by the World Intellectual Property Organization, pixel division by temporal factors in the driving method, in addition to pixel division through changes in element configuration, shape and orientation method in the pixel area of the display device The concept of pixel division by delay time is disclosed.

However, in order to divide these various pixels, the form, composition, coupling relationship, processing method, and operation method of the components of the liquid crystal display must be changed by comparing with the conventional technology before pixel division, and production, operational, and maintenance difficulties due to such conversion There are difficulties, and this may cause new problems such as image quality and durability of the liquid crystal display device.

Republic of Korea Patent Registration No. 10-0494706 Republic of Korea Patent Publication No. 10-2016-0127856 Republic of Korea Patent Registration No. 10-0966230 Republic of Korea Patent Registration No. 10-0476044 Republic of Korea Patent Registration No. 10-0300168 WO 2014042425 A1

The present invention is to improve or solve the problem of the high-speed response of the above-described active drive type liquid crystal display device, and an object of the present invention is to provide a liquid crystal display device capable of driving at a high speed of 120 Hz by reducing response time in an ultra-high resolution liquid crystal panel. .

The present invention is preferably a liquid crystal display device having a fast response time enabling a resolution of 1000 to 2000 ppi or higher and a refresh rate of 120 Hz or more in a 3-inch display for HMD having ultra-high-speed, high-speed response characteristics. It aims to provide.

Another object of the present invention is to provide a liquid crystal display device having a fringe field switching structure which is formed of high resolution and can easily improve viewing angle characteristics by achieving pixel division through a simple configuration.

The liquid crystal display device of the present invention for achieving the above object,

A lower substrate on which the first polarizing plate is installed, an upper substrate on which the second polarizing plate is installed, a liquid crystal positioned between these upper and lower substrates, a thin film transistor installed on the lower substrate and a gate line connected to the gate electrode of the thin film transistor to drive the same , In a liquid crystal display device having a data line connected to a source electrode and a pixel electrode connected to a drain electrode,

In each pixel area, a first common electrode forming a through hole (slit) with an insulating layer interposed over a flat pixel electrode on a lower substrate, and a second common electrode operated with the same polarity as the common electrode are provided on the upper substrate. When a voltage is applied between the pixel electrode and the first common electrode and the second common electrode, the liquid crystal arrangement at the boundary (fringe) of the through hole is switched from vertical or horizontal to inclined state to pass light,

The through-hole is characterized in that the liquid crystal is inclined in at least three different normal directions when a light-transmitting voltage is applied in a single pixel or across the same color pixels adjacent to each other by the installation direction of the peripheral portion.

In the present invention, in order to substantially incline the liquid crystals in three or more different normal directions, it can be exemplarily defined that the shape of the through hole is formed so that the liquid crystal inclined region in any one direction does not exceed 34% of the total liquid crystal inclined region, In this case, the liquid crystal inclined region may be exemplarily defined as a region in which the light transmittance is substantially 10% or more of the maximum light transmittance in the pixel, thereby substantially transmitting the light.

 In the present invention, the through hole may be formed of a triangular, rhombus, rectangular, pentagonal or more regular polygon, a slanted line slit, or an oval or circle,

In the present invention, it is preferable that the upper substrate and the lower substrate are provided with a circular or wave-shaped polarizing plate in which an outer linear polarizing plate and an inner quarter-wave retardation plate are combined to alleviate light leakage and viewing angle problems.

The liquid crystal display device of the present invention may be a head mounted display (HMD).

In the liquid crystal display device of the present invention, the boundary between the pixels on the upper substrate may be formed of a transparent film or a semi-transparent film without a separate impermeable film.

In the present invention, the liquid crystal employs a positive liquid crystal having a positive dielectric anisotropy, and the initial liquid crystal alignment may be a vertical alignment state.

The present invention may be a liquid crystal display device used in an HMD having a pixel pitch of 8 micrometers or less, a through hole is located in the center of a pixel, and a distribution of light intensity when a light-transmitting voltage is applied to the pixel, and a boundary of the pass hole A point having a light intensity of 10% of the light intensity at the maximum light intensity position within the pixel may be made to be located at a position that is at least 1 um away from the boundary between the pixels.

In the present invention, the first common electrode and the second common electrode may be driven in conjunction with the same voltage.

In the present invention, the second common electrode may be formed with a through hole in the central portion as the first common electrode has a through hole. At this time, the through hole of the second common electrode has a shape similar to the pattern of the first common electrode, but it is preferable to have a slightly enlarged shape from the center in the normal direction of the boundary of the through hole.

According to the present invention, the response speed of the liquid crystal display device is increased, so that a high-speed 120Hz refresh rate can be driven even in an ultra-high resolution liquid crystal panel.

According to the present invention, it is possible to implement an HMD suitable for a game or a virtual reality screen by enabling an ultra-high-definition high-speed response, and preferably an HMD having a high-resolution 1000 to 2000 ppi or higher and a fast response time enabling a refresh rate of 120 Hz or higher. have.

According to the present invention, it is possible to easily achieve the pixel division by the liquid crystal direction while not complicating or forcing the manufacturing process or the liquid crystal display device configuration and driving method using the feature structure of the through hole of the common electrode of the existing FFS type liquid crystal display device. Therefore, it is possible to improve the viewing angle characteristic, especially in the vertical alignment method.

1 is a plan view of a pixel portion of a liquid crystal display according to an exemplary embodiment, as viewed from above, showing a slant (pass through) pattern of a first common electrode and an inclined direction of liquid crystal molecules in a pattern fringe (boundary);
FIG. 2 is a cross-sectional view showing a cross-section of a pixel portion of a liquid crystal display according to an exemplary embodiment of the present invention through a cross-section along line II 'of FIG. 1;
3 is an exploded perspective view schematically showing the configuration of a liquid crystal display device in which a polarizing film and a compensation film are further combined on the outside of the unit cell as shown in FIG. 2;
4 and 5 are cross-sectional views showing a cross section perpendicular to the slit direction to represent the liquid crystal arrangement around the slit of the first common electrode of the vertically aligned liquid crystal display device of the present invention, before and after voltage is applied to each pixel electrode. Sections showing the state of the later,
6 is a result of experiments while changing the voltage applied to the pixel electrode under the condition that the slit pattern is positioned at the center of the pixel width direction in one configuration example of the simplified liquid crystal display device, going from the center to the periphery (x-axis direction) A graph showing the change in light transmittance,
7 is a comparative graph showing a change in transmittance with time while applying a constant voltage to a pixel electrode and blocking the voltage after a certain time for two cases of a conventional FFS type liquid crystal display as a comparative example with the liquid crystal display of the configuration example of FIG. ,
8 is a bar graph showing the difference between the rise time and the fall time according to the graph of FIG. 7,
9 and 10 are plan views showing the shape of the through hole of the common electrode over the pixel electrode and the inclination direction of the liquid crystal molecules at the boundary of the through hole as other embodiments of the present invention.
11 is a plan view showing a shape of a through hole of a common electrode and an inclined direction of liquid crystal molecules at each through hole boundary in a group of pixels adjacent to each other as another embodiment of the present invention.
12 is a cross-sectional view showing a cross section of a pixel portion of a unit cell of a liquid crystal display according to another embodiment of the present invention,
13 is a cross-sectional view showing a comparison between liquid crystal arrangements when a lighting voltage is applied to a pixel in an embodiment without a second common electrode through hole and an embodiment having a second common electrode through hole in the present invention;
14 is the center of the second common electrode through hole when the lighting voltage is applied to the pixel in the embodiment in which the second common electrode through hole is not formed and the second common electrode through hole is formed in different widths in the present invention. A graph showing the change in transmittance going from both ends to the width direction,
15 shows a change in transmittance of a pixel when a lighting voltage is increased in a pixel in an embodiment in which the second common electrode passing hole is not formed in the present invention and in the embodiments in which the second common electrode passing hole is formed in different widths. It is a graph.

Hereinafter, the present invention will be described in more detail with reference to drawings.

1 is a plan view of a pixel portion of a liquid crystal display to which a-Si TFT is applied, according to an embodiment of the present invention, a liquid crystal molecule in a slit (pass through) pattern and a pattern fringe (border) of the first common electrode. 2 is a cross-sectional view illustrating a pixel section of a liquid crystal display device according to an exemplary embodiment of the present invention through a cross section along line II ′ of FIG. 1.

Here, a gate electrode 121 and a gate line are formed on the lower substrate 111 through thin film deposition and patterning, a gate insulating layer 131 is formed thereon, a semiconductor film 132 is formed again, and a data line 141 is formed. ), The source electrode 142 and the drain electrode 143 are formed through a conductive layer stacking process and a patterning process to form thin film transistors for driving each pixel. At this time, the resistive contact layers 133 and 134 may be stacked over the semiconductor film 132 so that a resistive contact layer for conductive connection therebetween is provided at portions where the source electrode 142 and the drain electrode 143 overlap.

Of course, the specific configuration of the thin film transistor may be made in various forms in other ways known in the art. For example, in the above, a-Si TFT, as well as LTPS TFT, Oxide TFT, and other structures such as thin film transistors can be applied.

An interlayer insulating film 151 having a via hole is formed in the drain region over the thin film transistor, and a pixel electrode 161 is formed thereon. At this time, the interlayer insulating film 151 and the pixel electrode 161 are also formed through thin film lamination and patterning, and the pixel electrode 161 is formed in a flat plate shape in each pixel area and drains through the via 171 through the via hole. The electrode 143 is electrically connectable.

In the state in which the insulating layer 181 is formed over the pixel electrode 161, a first common electrode 191 pattern having a slit 192 having a long shape in the center of the pixel is formed. The pixel electrode 161 and the first common electrode 191 are insulated by the insulating layer 181.

Meanwhile, a color filter 231, a black matrix 221 layer, an overcoat film 241, and a second common electrode 251 are sequentially formed on the lower surface of the upper substrate 211 to form a second common electrode 251 in the drawing. It is formed at the bottom.

Although not shown, treatment for alignment may be performed on the lower substrate surface and the upper substrate surface that come into contact with the liquid crystal. As a method of vertically aligning the liquid crystal, various methods known in the art may be used. Here, an alignment layer may be formed for initial vertical alignment of the liquid crystal, material treatment for vertical alignment, and the like, and rubbing for orientation may not be performed separately in the material processing. As the alignment layer, a film made of polyimide can be used. Here, the pretilt angle is 90 degrees with respect to orientation.

The upper substrate and the lower substrate are respectively formed and aligned with a sealing material such as fritgrass in the periphery after being formed, and are coupled through the sealing. At this time, an injection hole through which liquid crystal is introduced is formed in part, and after the liquid crystal is filled, the injection hole is also sealed with a sealing material to form a liquid crystal display panel. Here, the liquid crystal uses a positive liquid crystal, and the initial liquid crystal arrangement is vertical, but may be horizontal depending on a method of forming an alignment layer.

Most of the substrate structure of the liquid crystal display device as described above may be made of the same material and method as conventionally known. However, the combination of the flat bottom pixel electrode 161 and the first common electrode 191 having a through hole 192 (slit) pattern formed thereon and the flat second common electrode 251 below the upper substrate The combination of the operation of applying the same polarity voltage or the same polarity voltage to the first common electrode and the second common electrode and the arrangement of the liquid crystal 300 form a characteristic configuration of the present invention.

For example, in the plan view, the through hole shows a rhombus shape with the square rotated 45 degrees, and the electric field or electric line is perpendicular to each side at the boundary of the four sides of the rhombus, which is the through hole when viewed from above (as viewed from the top view). Toward the normal direction, the four directions are rotated by 90 degrees from each other, and according to the electric field, the liquid crystals are arranged obliquely in the normal direction perpendicular to the boundary of the through hole pattern as shown in FIG. 1.

Accordingly, light passing through the region adjacent to the boundary line having the arrangement may be emitted to the outside through the liquid crystal panel, and the boundary portion of the through hole pattern becomes a portion emitting light when viewed from the front of the liquid crystal display. In addition, since the light emitting part has four different liquid crystal inclined directions, the pixel may emit light above a certain level and appear as a lit pixel even when viewing the screen from any direction, and the phenomenon that the image is distorted depending on the viewing angle is improved. Can be.

Characteristics of the vertical cross-section of the liquid crystal array in this configuration will be described later with reference to the cross-sectional view of FIG. 5.

Although not shown in FIG. 2, a first polarizing film on the outer surface of the lower substrate, a second polarizing film on the outer surface of the upper substrate, and a compensation film for compensating the viewing angle between the polarizing film and the unit cell, etc., are also formed as in a conventional liquid crystal display device. Can be.

3 is a perspective view schematically showing a configuration in which a polarizing film and a compensation film are installed in a unit cell as shown in FIG. 2. Here, the first polarizing film 20 and the second polarizing film 21 are installed such that the polarization directions form an angle of 90 degrees to each other, and the compensation film or retardation plate is perpendicular to the viewing direction when viewing the liquid crystal display device from the side than the front side. It is installed to compensate for light leakage or viewing angle characteristics due to the difference in angle between the arrays. For example, when the optical axis or the light-transmitting axis of the first polarizing film 20 is 0 degrees, the light-transmitting axis of the second polarizing film 21 is 90 degrees between the reference angle and the first polarizing film 20 and the unit cell 10. , The first compensation film 30 having a phase difference of 1/4 wavelength has a slow axis of 45 degrees or 135 degrees, and a phase difference of 1/4 wavelength between the second polarizing film 21 and the unit cell 10. 2 The compensation film 31 may be installed such that the delay axis is inclined by 135 degrees or 45 degrees.

The combination of a single polarizing film and a quarter-wave retardation plate with a delay axis that is 45 degrees different from its light transmission axis can be considered as a kind of circular polarizing plate that converts ordinary light into circularly polarized light. It can be seen in various liquid crystal displays to improve the viewing angle and light leakage characteristics and improve the transmittance of the visible light range by arranging the light-transmissive axes at an angle of 90 degrees to each other.

4 and 5 schematically show the arrangement of the liquid crystal around the diamond-shaped slit of the first common electrode in a cut surface similar to FIG. 2 of one embodiment of the present invention, perpendicular to the slit direction in each of the initial state and the lit state These are cross-sectional views showing one section.

However, a color filter layer, an overcoat film, a data line and a gate line, a thin film transistor structure, and the like, as shown in FIG. 1 are not shown separately, but are considered to be included in the upper substrate 210 or the lower substrate 110.

Referring to FIG. 4, since no voltage is applied to the pixel electrode 161, when the potential difference is not applied between the pixel electrode 161 and the first and second common electrodes 191 and 251, the liquid crystal 300 is vertically and horizontally applied. Either a directional or vertical arrangement.

Referring to FIG. 5, a voltage is applied to the pixel electrode 161 and a potential difference is applied between the pixel electrode 161 and the first and second common electrodes 191 and 251, and a slit of the first common electrode 191 ( Looking at the electric flux line passing through the width (indicated by g), the slits are inclined in the fringe region, and thus the liquid crystal deviates from the vertical arrangement and forms some inclination with the vertical lines. When the lighting voltage is applied, the electric field flux started from the pixel electrode passes through the slit 192 and then bends upwards, so that the lower portion enters the upper surface of the first common electrode 191 and the upper portion vertically forms the lower surface of the second common electrode 251. It becomes the form to go into.

The light transmittance has the maximum horizontal electric field at the slit fringe, and is maximized because the liquid crystal array is deformed to the maximum in the horizontal direction to form a vertical and maximum inclination angle.

When the liquid crystal 300 deviates from the vertical arrangement state and forms some inclination, the backlight light of the liquid crystal display is polarized into the first type passing through the first polarizing plate 115 in the region around the slit pattern fringe of the pixel according to this arrangement change. As light passes through the liquid crystal layer in the inclined array, a change in polarization state occurs, so that at least a portion of the light can be emitted to the outside through the second polarizing plate 261, and the pixel is turned on.

In this embodiment of the present invention, the change of the liquid crystal arrangement uses an initial vertical arrangement state, and corresponds to a band-type transformation among three elastic deformations of the liquid crystal. In the liquid crystal properties, the elastic modulus of the band-type elastic deformation is larger than that of the twist-type or spray-type deformation, so that the speed of change and restoration is faster than that of most liquid crystal arrays that mainly use the twist-type deformation. do.

The responsiveness of the liquid crystal display device according to the aspect of the liquid crystal arrangement in the present invention and the change in the recovery speed of the liquid crystal have a structure similar to that of the present invention and are estimated through simulation in a configuration example that is thought to have almost the same characteristics in addition to the viewing angle characteristics. Can be. This configuration example is almost the same as the present invention in the arrangement mode of the liquid crystal and the type of elastic deformation, and the slit shape has a simple one-shaped structure.

6 is a result of experiments while changing the voltage applied to the pixel electrode under the condition that the slit pattern is positioned at the center of the pixel width direction in one configuration example of the simplified liquid crystal display device, going from the center to the periphery (x-axis direction) It shows the pattern of light transmittance changing or distribution of light transmittance.

Here, while forming the display, the pixel pitch in the left-right direction is 8 micrometers (μm), the pixel electrode width is 5 μm, and the slit width (g) is approximately 2 μm, and the data line is positioned at the boundary between the pixels.

The simulation performance was confirmed while applying or blocking voltage to the pixel electrode. Here, the width of the pixel electrode is slightly reduced compared to that of the pixel electrode formed in substantially the entire width of the pixels in the embodiments of FIGS. 1 and 2. However, the width of the pixel electrode is equal to or greater than the size of the slit width g.

As the width of the pixel electrode is changed, the storage capacity C _st between the pixel electrode and the common electrode is changed, so the adjustment of the width of the pixel electrode can be made according to the amount of storage capacity required.

The space between the upper substrate and the lower substrate (cell gap: d) is 4 μm here, and a liquid crystal material is injected and filled with liquid crystal. Here, as the liquid crystal, a liquid crystal having a positive dielectric anisotropy, which has properties that are arranged parallel to the electric field direction when an electric field is applied, is used.

In more detail, in this embodiment, the liquid crystal 300 has an abnormal refractive index (n _e ) 1.6041, a normal refractive index (n _o ) 1.4893, a parallel dielectric constant (ε _// ) 12.3, and a vertical dielectric constant (ε⊥) 4.1 based on 20 ℃. , Splay elastic modulus (K ₁₁ ) 16.9pN, twist elastic modulus (K ₂₂ ) 8.42pN, band elastic modulus (K ₃₃ ) 19.2pN, rotational viscosity γ (rotational viscosity) of 80mPa · s was used.

According to this graph, the slit fringe has the maximum light transmittance, and the light transmittance decreases as it goes to the border between pixels, and when it reaches about 1 um at the border, the light transmittance is less than 0.01 and it is significantly less than 10% of the maximum light transmittance. It can be seen that the transmitted light disappears.

7 is a comparative graph showing a change in transmittance with time while applying a constant voltage to a pixel electrode and blocking the voltage after a certain time for two cases of a conventional FFS type liquid crystal display as a comparative example with the liquid crystal display of the configuration example of FIG. As a result, the difference in response speed obtained by applying the voltage corresponding to the lighting signal can be confirmed. As shown in FIG. 8, the difference between the rise time and the fall time according to the graph of FIG. 7 is represented by a bar graph.

In these graphs, the existing FFS type liquid crystal display device, which is a comparative example with the liquid crystal display device of the configuration example, has a different pixel structure, so it cannot be tested under the same conditions, and the liquid crystal behavior in the pixel structure of the present invention is not the same condition. Through this, it can be confirmed that the response speed can be driven very quickly.

In these graphs, a configuration example is represented by UFS-VA, a comparative example is represented by FFS, and comparative examples are classified according to the size of the slit width (g) and the pixel electrode width (w). In the comparative examples, the upper substrate has an electrode structure of the FFS method without a second common electrode or a counter electrode, the liquid crystal alignment has a horizontal alignment, and the slit width formed on the pixel electrode or the common electrode is l, and a plurality of parallel to each other. The width (width) of the pixel electrode (including the case where the pixel electrode is on and the slit is formed in the pixel electrode) on which the dog is installed is expressed as w. In this comparative example, substantially the same result can be obtained even when the common electrode and the pixel electrode are arranged interchangeably (when the common electrode is on and the slit is formed on the common electrode).

The response speed of this configuration example is several times faster than the response speed of the comparative example. In general, considering that it is possible to significantly reduce the rise time through overvoltage driving, the most important effect on the response speed when displaying a continuously changing image on the display device The τ _f , which can be called the part giving the speed, is more than 10 times faster, and of course, a liquid crystal display having such a response speed can be used for realizing a fast video having a frame rate of 120hz or higher, virtual reality, and displaying a game screen.

In addition, as mentioned above, the numerical values obtained in these configuration examples can be sufficiently obtained in the embodiments of the present invention, which differ only slightly in the direction of the liquid crystal inclination when compared with the configuration examples, so that the response speed of the liquid crystal is not substantially different. The embodiment of the invention may also be sufficiently used for realizing a fast video having a frame rate of 120hz or more, realizing a three-dimensional image in virtual reality, and displaying a gay screen.

9 and 10 are plan views showing a shape of a through hole of a common electrode over a pixel electrode as other embodiments of the present invention. Here, it can be seen that the inclined direction of the liquid crystal molecules at the periphery or fringe of these through holes is directed in the normal direction perpendicular to the boundary of the through holes.

In the embodiment of Fig. 9, other conditions are substantially the same as those of Fig. 1, and the through holes 192 are changed from lozenges to circles. When the transmission voltage is applied to the pixel electrode, the inclination direction of the liquid crystal is different at all positions in the periphery of the circle depending on the direction of the electric line or the electric field passing through the through hole 192. That is, when viewed from above, the inclined direction of the liquid crystal points to 360 degrees, so when viewing the panel from the front of the liquid crystal display device, the light emitted from the pixel can be seen when the pixel is lit from any direction in the front, and the viewing angle characteristics It becomes better.

Of course, even when the through hole 192 is a regular octagonal shape or a regular hexagonal shape, the inclination direction of the liquid crystal is evenly divided into octagonal or hexagonal shapes, substantially depending on the direction, thereby reducing the dependency of the visible and invisible direction of the lighting pixel and widening the viewing angle. It can be considered that the pixel division is performed according to the inclination direction of the liquid crystal.

The other condition of FIG. 10 is substantially the same as that of the embodiment of FIG. 1, and the through hole 192 is changed from a lozenge to a slit like a bend of a simple one character.

Although the shape of the lozenge formed by the through hole in FIG. 1 and the angled slit in FIG. 10 are completely different, it can be seen that the four directions formed by the electric line passing through the through hole in the peripheral portion when the lighting voltage is applied to the pixel electrode are substantially the same. have.

However, when looking at the size of the through hole 192, the length in the up and down direction is the same as the lozenge, and the left and right width is almost half the size of the lozenge. Therefore, this form is advantageous for applying to a high-definition display in which the pixel density increases and the pixel size itself decreases. That is, in the case of making a slit with a reduced width of the through hole compared to making a through hole in a rhombic shape, the possibility of interference between this slit pattern and other patterns is reduced, thereby reducing defects and increasing ease in the manufacturing process. , It reduces the possibility that the light from the slit fringe crosses the pixel boundary and creates a crosstalk phenomenon that illuminates adjacent pixels.

11 is a plan view showing a shape of a through hole 192 of a common electrode in a group of pixels adjacent to each other as another embodiment of the present invention. Here, it can also be seen that the inclined direction of the liquid crystal molecules at the boundary of each of these through holes is a normal direction perpendicular to the boundary line.

In this embodiment, the slit of one pixel is formed in a hatched shape with a simple 45-degree slope, but when viewing multiple pixels, it can be seen that the inclined direction of the hatch is different from 45 degrees to the left and 45 degrees to the right.

For convenience of explanation, it is assumed that one pixel formed long vertically as shown in FIG. 2 is divided into two short pixels, upper and lower, and these two pixels are pixels that are in charge of the same color. Considering that the same lighting state is achieved in, it can be seen that these two pixels correspond substantially to one pixel, and the slits of these two pixels can be considered to be the angled slits of FIG. 10 when integrated as a whole.

The inclination direction of the liquid crystal in the integrated slit and the effect thereof can be seen as in FIG. 10, and the display device as a whole has an effect of widening the viewing angle.

However, the above assumptions and explanations are for convenience, and it can be seen that, in practice, two pixels having the same color and different slit inclination directions are disposed vertically adjacent to each other without being vertically arranged.

Since such an embodiment changes the liquid crystal direction through a group of pixels composed of a plurality of adjacent pixels, it can be called a multi-pixel multi-domain method by distinguishing it from a simple multi-domain (pixel division) method.

12 is a cross-sectional view illustrating a cross section of a pixel portion of a unit cell of a liquid crystal display according to another embodiment of the present invention. In this embodiment, the through hole 252 is formed in the second common electrode of the upper substrate as well as the through hole in the first common electrode of the lower substrate.

At this time, the passage hole 252 of the second common electrode has a shape similar to the pattern of the first common electrode, but the boundary line of the passage hole moves slightly from the center to the periphery in the normal direction, so that the width is slightly expanded. Preferably, if the width of the through hole of the first common electrode is 2 micrometers, the width of the through hole of the second common electrode is 3 micrometers or 4 micrometers.

When the pass hole 252 is also formed in the second common electrode, the vertical alignment of the liquid crystal is disturbed in the pixel region where the pass hole is formed. Therefore, light passes slightly larger at the boundary of the first common electrode through hole of the pixel, and the light region increases to improve transmittance. However, if the through hole is too wide, the effect is similar to that of an FFS type liquid crystal display device in which the second common electrode is not formed, and the liquid crystal operation time may be influenced when the pixel is switched on. It is preferable that the width of the formed through hole is not more than 1/2 of the pixel width.

13 is an embodiment in which a pattern is not formed in the second common electrode as shown in FIG. 2 of the present invention, and in the embodiment in which a through hole 252 pattern is formed in the second common electrode as shown in FIG. 12, the lighting voltage is applied to the pixel. When the liquid crystal arrangement type difference is compared with each other, the above description is visually illustrated in a cross-sectional view.

FIG. 14 is a pixel in an embodiment in which a pattern is not formed in the second common electrode of an individual pixel of the present invention, and in embodiments in which a through hole 252 pattern is formed in a width of 3 micrometers and 4 micrometers, respectively. It is a graph showing a form in which the transmittance changes while going from the center of the second common electrode pattern to both ends in the width direction when the lighting voltage is applied to the. According to this graph, even if the lighting voltage is the same, it can be seen that the transmittance is improved compared to the previous embodiments in which the through hole pattern is not formed on the second common electrode, and when the through hole pattern is formed on the second common electrode, the pattern It can be seen that the transmittance is improved more when the pattern width is 4 micrometers than when the width is 3 micrometers. This can be seen as a matter of course as the area in the pixel in which the liquid crystal array is changed to transmit light increases.

15 is an embodiment in which the through hole pattern is not formed in the second common electrode of the individual pixels of the present invention and in the embodiments in which the through hole 252 pattern is formed in the width of 3 micrometers and 4 micrometers in the second common electrode. It is a graph showing the form in which the transmittance of a pixel changes while the lighting voltage is increased to the pixel. The transmittance increases as the lighting voltage (the difference voltage between the pixel electrode and the common electrode) higher than the threshold voltage at which lighting is performed increases, and in the same lighting voltage, the one where the through hole is formed in the second common electrode and the second common electrode through hole It can be seen that the wider the pattern width, the higher the transmittance.

On the other hand, in the above, the case where the liquid crystal is vertically oriented in the initial state is mainly described, and it is common to see a larger effect in the case of vertical alignment, but even when it is horizontally oriented, the liquid crystal arrangement is not horizontal but has an inclination even when horizontally aligned. The invention can be applied in the same way.

In the above, the present invention has been described through limited embodiments, but the present invention is not limited to these specific embodiments, which are merely illustratively described to help understanding of the present invention.

Therefore, a person having ordinary knowledge in the field to which the present invention pertains can make various changes or application examples based on the present invention, and it is natural that such modifications and application examples belong to the appended claims.

10: unit cell 20, 115: first polarizing plate
21, 261: 2nd polarizing plate 30, 31: compensation film (phase difference plate)
111: lower substrate 251: second common electrode
121: gate electrode 122: gate line
131: gate insulating film 132: semiconductor film
133, 134: resistive contact layer 141: data line
142: source electrode 143: drain electrode
151: interlayer insulating film 161: pixel electrode
171: via 181: insulating film
191: first common electrode 192: through hole (slit: slit)
195, 271: alignment film (orientation layer)
211: upper substrate 221: black matrix
231: color filter 241: overcoat film
252: through hole (the second common electrode through hole)

Claims (9)

A lower substrate on which the first polarizing plate is installed, an upper substrate on which the second polarizing plate is installed, a liquid crystal positioned between these upper and lower substrates, a thin film transistor installed on the lower substrate and a gate line connected to the gate electrode of the thin film transistor to drive the same , In a liquid crystal display device having a data line connected to a source electrode and a pixel electrode connected to a drain electrode,
In each pixel area, a first common electrode forming a through hole (slit) with an insulating layer interposed over a flat pixel electrode on a lower substrate, and a second common electrode operated with the same polarity as the common electrode are provided on the upper substrate. When a voltage is applied between the pixel electrode and the first common electrode and the second common electrode, the liquid crystal array of the fringe of the through hole is switched from vertical or horizontal to an inclined state to pass light,
The through hole is formed so that the liquid crystal is inclined in at least three different normals (lines perpendicular to the tangent to the peripheral part) when a light-transmitting voltage is applied in a single pixel or in the same color pixel adjacent to each other by the installation direction of the peripheral part. Liquid crystal display device. According to claim 1,
The liquid crystal employs a positive liquid crystal having a positive dielectric anisotropy, and the initial liquid crystal alignment forms a vertical alignment state. According to claim 1,
In order for the liquid crystal to be inclined in different normal directions of 3 or more, a through hole shape is formed so that the liquid crystal inclined region in any one direction does not exceed 34% of the total liquid crystal inclined region,
The liquid crystal display device is characterized in that the liquid crystal inclined region is a region in which the light transmittance is 10% or more of the maximum light transmittance in the pixel. According to claim 1,
A quarter-wave retardation plate is installed at a position between the upper substrate and the second polarizing plate and between the lower substrate and the first polarizing plate, and the transmission axis of the polarizing plates adjacent to each other and the slow axis of the retardation plate are 45 degrees. A liquid crystal display device, characterized in that it is installed to form a slope and to form a 90-degree slope between the delay axes of the two retardation plates. According to claim 1,
The through hole is a liquid crystal display device, characterized in that one of a rhombus shape, a line shape, a triangular or higher polygon, a circular shape, and an oval shape. According to claim 1,
The through-hole is formed to form a slit in a slant across the same color pixels that are successive to each other. According to claim 1,
The liquid crystal display device is a liquid crystal display device for HMD having a pixel pitch of 8 micrometers or less, and the through hole is located at the center of the pixel,
The first common electrode and the second common electrode are driven by being interlocked with the same voltage. According to claim 1,
A liquid crystal display device characterized in that a through hole is formed in the center of the second common electrode as well. The method of claim 8,
The pattern of the through hole of the second common electrode is common to the pattern of the through hole of the first common electrode when viewed in a direction perpendicular to the plane of the liquid crystal display,
The liquid crystal display device of claim 1, wherein the width of the first common electrode is widened by moving from the center to the outside in the normal direction of the boundary line of the through hole, but the width does not exceed 1/2 of the pixel width.

Images