KR101026035B1 - Viewing angle switching liquid crystal display device using vertical electric field and optically isotropic liquid crystal mixture - Google Patents

Abstract

The present invention relates to a viewing angle control liquid crystal display device which is driven by dividing one panel into a main pixel region representing a main image and an auxiliary pixel region adjusting a viewing angle without an additional panel, and is optically isotropic to anisotropic by an electric field. The present invention relates to a liquid crystal display device in which a fringe direction electric field is formed in a main pixel and a vertical electric field is formed in an auxiliary pixel by using a liquid crystal having a variable amount of dielectric anisotropy.

Optical isotropic, optically anisotropic, liquid crystal display device, viewing angle adjustment.

Description

Viewing angle controllable liquid crystal display device using vertical electric fields and optically isotropic liquid crystal mixtures

The present invention uses a liquid crystal having a positive dielectric anisotropy that varies optically isotropically anisotropically by an electric field, and adjusts the viewing angle using a vertical electric field and an electrode representing a main image using a fringe electric field without further processing. The present invention relates to a liquid crystal display device for controlling a viewing angle by using a phase delay value different according to a viewing direction by varying directions of birefringence induced by a method of separately patterning electrodes on one substrate.

The liquid crystal display device has been developed to focus on the wide viewing angle characteristic to overcome the limitation of the twisted nematic (TN) mode to date, and among the typical driving schemes having the wide viewing angle characteristic, IPS (in- There are plane switching mode and fringe field switching mode. Among them, the FFS mode not only shows good optical characteristics and transmittance but also has a low driving voltage, which is particularly suitable for small portable devices. However, in the case of portable devices, when the liquid crystal display device having the wide viewing angle characteristic is used in a public place, information is naturally exposed, which causes problems due to leakage of personal information or privacy in the information society. A study on the liquid crystal display device having the characteristics has been proposed. In the case of a liquid crystal display device having a narrow viewing angle feature, since information is only displayed in front of the user for privacy protection, if the environment is changed and a wide viewing angle feature is required, another problem in using the display is caused, and thus the application field is very narrow. For this reason, recently, a liquid crystal display device capable of adjusting a viewing angle in which switching between a wide viewing angle feature and a narrow viewing angle feature is freely developed has been developed.

Conventional liquid crystal display device that can adjust the viewing angle is thick because the two liquid crystal panels are used, the problem of high manufacturing cost. In addition, the nematic liquid crystal phase mainly used in such a liquid crystal display device uses a method in which the optical axis of the liquid crystal is initially arranged in advance in a batch to change the polarization state of light transmitted from the light source according to the direction of the liquid crystal molecules. Therefore, rubbing process is inevitable. Such a rubbing process is an operation which rubs the surface of the oriented film apply | coated to the board | substrate surface which contact | connects a liquid crystal with cloth etc., and this causes the cost of a yield fall, or the quality deterioration of a liquid crystal display element.

Accordingly, an object of the present invention is to provide a liquid crystal display device capable of adjusting a viewing angle that can effectively adjust a wide viewing angle feature and a narrow viewing angle feature by dividing an area representing a main image and an area for adjusting a viewing angle on one panel without an additional panel. will be.

Another object of the present invention is to improve the process yield by using an optically isotropically anisotropic liquid crystal that can eliminate the rubbing process to reduce the process yield and increase the reaction rate of the liquid crystal has a good driving characteristics through fast response speed It is to provide a liquid crystal display device.

As a technical means for solving the above-described problems, the present invention provides a pixel region (hereinafter referred to as a main pixel) representing an electrode structure of one pixel in a conventional FFS mode and an auxiliary pixel region (hereinafter referred to as an auxiliary pixel) for adjusting a viewing angle. (Called a pixel). In the main pixel, the birefringence is induced according to the electric field direction in the conventional FFS mode to express the main image. The auxiliary pixel is patterned by using a common electrode and a pixel electrode as upper and lower substrates with transparent ITO (indume tin oxide) electrodes. Narrow viewing angle mode can be realized by inducing birefringence in the vertical direction due to the vertical electric field and positive dielectric anisotropy in the optically isotropic liquid crystal mixture when voltage is applied to the pixel. Provided is a liquid crystal display device capable of adjusting a viewing angle using a panel.

According to the present invention, since the liquid crystal display device for dividing the main pixel and the auxiliary pixel on one panel to adjust the viewing angle without an additional panel is provided, the liquid crystal display device having a thin thickness, light weight, and a reduction in manufacturing cost is possible. Can make

Moreover, according to this invention, since a rubbing process is not necessary, the fall of a yield by the rubbing process and the fall of the element quality can be avoided.

In addition, according to the present invention, by using a liquid crystal that is optically isotropically anisotropically changed by voltage application, a response speed of μs is realized, and thus, a natural video can be realized as compared with a nematic liquid crystal.

In addition, according to the present invention, since a strong fringe electric field is formed in the lower portion, there is an effect that can drive the device at a lower driving voltage than the IPS mode driving.

The present invention provides an optically isotropic to anisotropic method by an electric field in implementing a viewing angle control liquid crystal display device in which one panel is divided into a main pixel region representing a main image and an auxiliary pixel region adjusting a viewing angle without an additional panel. Using liquid crystals with varying amounts of dielectric anisotropy, the amount of induced birefringence is controlled by using a fringe direction electric field in the main pixel and a vertical electric field in the auxiliary pixel to adjust the degree of birefringence induced in the dark and the front of the viewing angle. The present invention relates to a liquid crystal display device that enables viewing angle adjustment by adjusting.

Example 1

In Example 1, a pixel is divided into a main pixel and an auxiliary pixel, and the main pixel is a pixel formed in a direction parallel or perpendicular to a gate wiring or a data wiring with a common electrode formed in a planar shape on a lower substrate, and an insulating layer therebetween. The fringe electric field due to the potential difference between the electrodes, and the auxiliary pixel controls the light leakage in the dark state in the vertical, vertical, left and right viewing angle directions by using the vertical electric field by the flat electrodes formed under the upper plate and the lower plate, respectively.

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

1 is a structure of a blue phase liquid crystal. As shown in the figure, birefringence of the blue liquid crystal 5 occurs from the optically isotropic state (5-a) to the optically anisotropic state (5-b) according to the application of the electric field. The blue phase liquid crystal is a liquid crystal phase present in the temperature range between the cholesteric nematic phase and the isotropic phase, and has a first blue phase lattice structure and a second blue phase lattice structure (2-a, 2-b) and has a cylinder inside the lattice. (1-a) exists and the liquid crystal is twisted twice by the chiral dopant inside the cylinder (1-b), and is optically isotropic (5-a) before voltage is applied.

However, when the voltage is applied, as shown in Equation (1), the Kerr effect is generated by the external electric field and refractive index anisotropy is generated (5-b).

Δ n = λ KE ² (One)

(Δ n = induced refractive anisotropy, λ = wavelength of light source used, K = Kerr constant, E = electric field energy)

However, the contradiction region (3-c), that is, the defect region (3-a, 3-b), in which the liquid crystal is not present in the blue phase lattice structure because the temperature range where the blue phase liquid crystal is present is so narrow that it is not suitable for use as a display. UV light is used to form a photocurable polymer network (4) to expand the range of existence at room temperature.

Examples of the chemical structure of the liquid crystal, chiral dopant, monomolecular, and photoinitiator belonging to the liquid crystal layer which changes optically isotropic to anisotropic are as follows.

LCD

Chiral Dopant

-Single molecule-

-Photoinitiator-

2 is a plan view illustrating a liquid crystal display device capable of adjusting a viewing angle according to Embodiment 1 of the present invention. As shown, the first gate wiring 12-a and the second gate wiring 12-b are arranged so as to vertically intersect with one data wiring 11, and the first gate wiring 12-a. The first switching element 100 is formed at the intersection of the data wiring 11 and the second switching element 200 is formed at the intersection of the second gate wiring 12-b and the data wiring 11. It is. The first common electrode 9 connected to the first common electrode signal line 13 disposed in parallel with the first gate line 12-a and the first pixel electrode 8 connected to the first switching element 100. Is disposed in parallel with the data line 11 (or may be arranged in parallel with the first gate line 12-a), and is disposed in parallel with the second gate line 12-b. The second common electrode 10-a connected to the signal wire (not shown) is planar, and the second pixel electrode 10-b connected to the second switching element 200 is also planar.

3 is a cross-sectional view of a main pixel and an auxiliary pixel in a state before voltage application and in a narrow viewing angle mode after voltage application according to the present invention. As shown in the drawing, the liquid crystals in the main pixel A and the auxiliary pixel B regions representing the main image are in an optically isotropic state before voltage is applied, and thus, both show dark states. When voltage is applied, the liquid crystals in the region of the main pixel A induce birefringence according to the direction of the fringe electric field, and the light passing through the liquid crystal layer is emitted from the liquid crystal layer because the first pixel electrode 8 forms 45 degrees between the orthogonal polarizing plates. When the λ / 2 phase difference is sensed, the maximum transmittance occurs and the bright state is displayed. In addition, the liquid crystals of the auxiliary pixel B region may have birefringence depending on the direction of the vertical electric field formed between the second common electrode 10-b directly below the upper plate and the second pixel electrode 10-a directly above the lower plate. Since it is induced, light leakage occurs in the vertical, left, and right viewing angle directions, not the front, between the polarizers orthogonal to 45 and 135 degrees, and implements the narrow viewing angle mode.

4 is a plan view showing that a double domain is formed in the main pixel A region in one pixel. As shown, the first gate wiring 12-a and the second gate wiring 12-b are arranged so as to vertically intersect with one data wiring 11, and the first gate wiring 12-a. The first switching element 100 is formed at the intersection of the data wiring 11 and the second switching element 200 is formed at the intersection of the second gate wiring 12-b and the data wiring 11. It is. The second common electrode 10-a is in a planar shape, and the second pixel electrode 10-b connected to the second switching element 200 is also in a planar shape. The first common electrode 9 is formed in a planar shape on a lower substrate, and the first pixel electrode 8 formed with an insulating layer therebetween is formed on the first gate line 12-a in the main pixel A region. ) And a parallel domain with the data line 11 to form a double domain.

FIG. 5 is a plan view of a viewing angle control liquid crystal display having the same electrode structure and different signal wirings as in FIG. 2. As shown, one gate wiring 12 is arranged so as to vertically intersect the first data wiring 11-a or the second data wiring 11-b, and the gate wiring 12 and the first data wiring are arranged. The first switching element 100 is formed at the intersection of 11-a, and the second switching element 200 is formed at the intersection of the gate line 12 and the second data line 11-b. The electrode pattern of the main pixel A region and the shape of the electrode of the auxiliary pixel B region are shown in FIG. 2.

FIG. 6 is a pixel structure diagram in which a color filter is not formed at a portion for adjusting a viewing angle in the same electrode structure as that of Example 1 to produce white color. As shown, R, G, and B color filters are formed in the main pixel 111 region, and color filters are not formed in the sub pixel 222 region, thereby adjusting the voltage of the region for adjusting the viewing angle by producing white color. Because it can display, the text overlaps or the image overlaps when viewing the screen in the left and right directions. The gate wiring 12, the switching elements 100 and 200, and the data wirings 11-a and 11-b are respectively formed to apply a voltage to the main pixel 111 and the auxiliary pixel 222 separately. The black matrix 14 is formed to cover them.

7 is a computer simulation result showing an isoluminescent curve in the dark state in the wide viewing angle mode and the narrow viewing angle mode in the electrode structure of FIG.

The simulation program used Shintech's LCD master. Light leakage value is the area where 70% and 50% 30% light leakage occurs based on the maximum light leakage in the wide viewing angle mode, respectively. As shown, (A) shows the degree of light leakage in the dark state in the wide viewing angle mode, and (B) shows the degree of light leakage in the dark state in the narrow viewing angle mode. The maximum light leakage in the wide viewing angle mode is expressed as 0.016128. The maximum light leakage in the narrow viewing angle mode is expressed as 0.31129. The light leakage in the wide viewing angle mode is small, whereas in the narrow viewing angle mode. It can be seen that the degree of light leakage from the left and right direction is very large.

Example 2

In Embodiment 2, three main pixels representing a main image by dividing one pixel into four unit pixels include red (hereinafter referred to as R), green (hereinafter referred to as G), and blue (hereinafter referred to as B). The auxiliary pixel for coating the color filter and adjusting the other viewing angle relates to a liquid crystal display device capable of adjusting the viewing angle driven by white (hereinafter referred to as W) without coating the color filter.

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

8 is a plan view illustrating a liquid crystal display device capable of adjusting a viewing angle according to Embodiment 2 of the present invention. As shown, the viewing angle adjusting liquid crystal display of the present invention shows a liquid crystal display capable of adjusting the viewing angle having four unit pixels by adding a unit pixel for adjusting the viewing angle. The unit pixels of R, G, and B for displaying information include a first common electrode 9 and a first pixel electrode 8, and are driven by the first switching element 100 and the auxiliary pixel W 222. The unit pixel of includes a second common electrode 10-a and a second pixel electrode 10-b, and is driven by the second switching element 200.

9 is a plan view of another structure for explaining the liquid crystal display device capable of adjusting the viewing angle according to Embodiment 2 of the present invention. In order to implement one unit pixel, one gate line 12 and data line 11 are required, and a common electrode signal line 13 is disposed in parallel with the gate line 12, and R, G, A total of three first switching elements 100 and one second switching element 200 are formed in each of the auxiliary pixels, one in each main pixel.

In addition, the shape of the first common electrode of the second embodiment and the direction of the first pixel electrode are the same as those of the first embodiment, and the three main pixel areas representing the main image form R, G, and B color filters, One auxiliary pixel area to be adjusted does not form a color filter so that the voltage of the area for adjusting the viewing angle can be varied by displaying W so that gray scales can be displayed in the viewing angle direction. You can make it look

In the above described as a preferred embodiment of the present invention, but is not limited to the above-described embodiment of the present invention, those who have ordinary knowledge in the field of the invention without departing from the gist of the invention claimed in the claims Anyone can make a variety of variations.

1 is a structural diagram of a blue phase liquid crystal applied to the present invention.

2 is a plan view for explaining a viewing angle control liquid crystal display device according to a first embodiment of the present invention.

3 is an optical schematic diagram of an optically isotropic and anisotropic change state by applying an electric field of a blue phase liquid crystal according to Example 1 of the present invention, that is, a voltage application on / off state.

4 is a plan view illustrating a viewing angle control liquid crystal display device in which the dual domain electrode structure is formed in the main pixel region in the FIG. 2 structure; FIG.

5 is a plan view of a viewing angle control liquid crystal display device having the same electrode structure and different signal wirings as in FIG. 2.

FIG. 6 is a pixel structure diagram in which a color filter is not formed at a portion for adjusting a viewing angle in an electrode structure as in Embodiment 1 of the present invention, to give white color; FIG.

7 is a computer simulation result showing an isoluminance curve in the dark state in the wide viewing angle mode and the narrow viewing angle mode in the electrode structure of FIG.

8 is a pixel structure diagram in which a color filter is not formed at a portion for adjusting a viewing angle in an electrode structure as in Example 2, thereby giving white color;

FIG. 9 is another pixel structure diagram in which a color filter is not formed at a portion for adjusting the viewing angle in the electrode structure as in Example 2 to give white color; FIG.

Claims (4)

In the two substrates spaced apart from each other at regular intervals, A lower substrate; A first common electrode having a planar shape positioned on a portion of the lower substrate; An insulating layer disposed on the first common electrode; A first pixel electrode having a lattice shape positioned on the insulating layer by as much as the first common electrode region; A second pixel electrode patterned in a planar shape located in the remaining area above the insulating layer where the first pixel electrode is not located; A liquid crystal layer on the first pixel electrode and the second pixel electrode, the liquid crystal layer having a positive dielectric anisotropy optically isotropically anisotropically changed by an electric field; An upper substrate; A second common electrode formed by patterning an electrode having a planar shape at the same position as the size of the second pixel electrode under the upper substrate; Forming two gate wires and one data wire to transmit a signal to each pixel; Two switching elements each formed at an intersection of the two gate lines and one data line; An upper polarizer positioned on an upper portion of the upper substrate positioned at an angle of 45 degrees with a lattice direction between the first common electrode and the first pixel electrode; A viewing angle switching liquid crystal display device using a vertical electric field and an optically isotropic liquid crystal mixture, using a lower polarizing plate formed at an angle of 90 degrees with the upper polarizing plate and positioned below the lower substrate. In the two substrates spaced apart from each other at regular intervals, A lower substrate; A first common electrode having a planar shape positioned on a portion of the lower substrate; An insulating layer disposed on the first common electrode; A first pixel electrode having a lattice shape positioned on the insulating layer by as much as the first common electrode region; A second pixel electrode patterned in a planar shape located in the remaining area above the insulating layer where the first pixel electrode is not located; A liquid crystal layer on the first pixel electrode and the second pixel electrode, the liquid crystal layer having a positive dielectric anisotropy optically isotropically anisotropically changed by an electric field; An upper substrate; A second common electrode having a planar electrode patterned on the same position as a size of the second pixel electrode under the upper substrate; Forming two data lines and one gate line to transmit a signal to each pixel; Two switching elements each formed at an intersection of the two data lines and one gate line; An upper polarizer positioned on an upper portion of the upper substrate positioned at an angle of 45 degrees with a lattice direction between the first common electrode and the first pixel electrode; A viewing angle switching liquid crystal display device using a vertical electric field and an optically isotropic liquid crystal mixture, using a lower polarizing plate formed at an angle of 90 degrees with the upper polarizing plate and positioned below the lower substrate. In a liquid crystal display device having four unit pixels, A lower substrate; A first common electrode having a planar shape positioned on a portion of the lower substrate; An insulating layer disposed on the first common electrode; A first pixel electrode having a lattice shape positioned on the insulating layer by as much as the first common electrode region; A second pixel electrode patterned in a planar shape located in the remaining area above the insulating layer where the first pixel electrode is not located; A second pixel electrode patterned in a planar shape located in the remaining area where the first common electrode and the first pixel electrode are not located; A liquid crystal layer on the first pixel electrode and the second pixel electrode, the liquid crystal layer having a positive dielectric anisotropy optically isotropically anisotropically changed by an electric field; An upper substrate; A second common electrode formed by patterning an electrode having a planar shape at the same position as the size of the second pixel electrode under the upper substrate; One gate electrode, one signal line, and one switching element for each unit pixel; An upper polarizer positioned on an upper portion of the upper substrate positioned at an angle of 45 degrees with a lattice direction between the first common electrode and the first pixel electrode; A viewing angle switching liquid crystal display device using a vertical electric field and an optically isotropic liquid crystal mixture, using a lower polarizing plate formed at an angle of 90 degrees with the upper polarizing plate and positioned below the lower substrate. The method according to claim 1 or 2 or 3, A viewing angle switching liquid crystal display device using a vertical electric field and an optically isotropic liquid crystal mixture that forms an R, G, B color filter and the viewing angle is adjusted.

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