KR100777690B1 - Liquid crystal displays - Google Patents

Abstract

The liquid crystal display according to the present invention includes upper and lower substrates facing each other, and first and second electrodes generating an electric field to drive liquid crystal molecules are formed on inner surfaces of the substrates, respectively. The protrusions are formed on the electrodes at positions corresponding to each other, and an alignment layer covering the protrusions is formed on each electrode. In this case, the alignment layer is a horizontal alignment layer capable of orienting liquid crystal molecules substantially parallel to the substrate, and a layer of nematic liquid crystal material having positive dielectric anisotropy is injected between the alignment layers of the two substrates. Here, the liquid crystal molecules directly on the upper and lower alignment layer surfaces lie along the inclined surface of the protrusion and form a bent arrangement from the upper substrate to the lower substrate, and are arranged radially with respect to the surface of the substrate. Thus, by splitting and aligning the liquid crystal molecules into multiple regions in a radial manner, a uniform viewing angle can be obtained in any direction. Gray level inversion can be minimized. In addition, it is possible to have a wide viewing angle by symmetrically compensating for retardation of transmitted light.

Viewing angle, gradation inversion, phase delay, horizontal orientation, vertical orientation

Description

Liquid crystal display device {LIQUID CRYSTAL DISPLAYS}

1A and 1B schematically illustrate the structure and driving principle of a liquid crystal display device having a bending arrangement according to a first embodiment of the present invention.

 2 is a cross-sectional view schematically illustrating a structure of a liquid crystal display according to a second exemplary embodiment of the present invention.

3A and 3B schematically illustrate the structure and driving principle of a liquid crystal display device having a hybrid arrangement according to a third embodiment of the present invention.

4A and 4B schematically illustrate a structure of a liquid crystal display device having a hybrid arrangement according to a third embodiment of the present invention.

5A and 5B schematically illustrate the structure of a liquid crystal display device having a hybrid arrangement according to a fourth embodiment of the present invention.

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having a wide viewing angle.

In general, a liquid crystal display device injects a liquid crystal material between two substrates having an electrode generating an electric field, and applies an electric potential different from each other to form an electric field to change the arrangement of the liquid crystal molecules. It is a device that expresses an image by adjusting the transmittance.

Various methods have been developed to improve the response speed and the narrow viewing angle. The liquid crystal display including a hybrid aligned nematic (HAN) method or an optically compensated bend (OCB) method having horizontal and vertical alignment layers on two substrates has been developed. Presented.

However, the HAN method having a hybrid array in which liquid crystal molecules having positive dielectric anisotropy is changed from a vertical array to a horizontal array has an advantage of having a fast response speed, but still has a problem of having a narrow viewing angle. On the other hand, in the OCB method, a wide viewing angle can be obtained because the OCB has a vertical arrangement in a horizontal arrangement from the substrate to the center plane of the two substrates while being symmetrical with respect to the center plane of the two substrate surfaces. However, in order to obtain such a liquid crystal array, a bend array is obtained by initially applying a high voltage using a vertical alignment agent aligned in the same direction, but it is difficult to obtain a bend array by initially applying a high voltage. As a result, the bending arrangement is inferior in stability, so that the bending arrangement is broken under a certain voltage.

An object of the present invention is to provide a liquid crystal display device having a wide viewing angle and a stable bending arrangement.                         

An object of the present invention is to provide a liquid crystal display device having a fast response speed and a wide viewing angle.

In order to achieve this problem, the present invention is provided with a projection so that the liquid crystal molecules are arranged radially or concentrically with respect to the surface of the substrate.

Specifically, the liquid crystal display device according to the present invention includes first and second substrates on which first and second electrodes are formed to form an electric field, and have inclination angles on the first and second substrates facing each other. Protuberances are formed. In addition, they are horizontally oriented between the first and second substrates, are arranged vertically with respect to the first and second substrates, and have a pretilt angle by protrusions, which are symmetrically with respect to the centerline between the protrusions and the center plane of the substrate. A liquid crystal material layer of liquid crystal molecules arranged is injected.

In this case, the protrusions of the first and second substrates are preferably formed at positions facing each other, respectively, and the first and second alignment layers for horizontally aligning the liquid crystal material layer between each of the first and second substrates facing each other. Is formed.

The first and second alignment layers may be aligned in directions facing each other, and the liquid crystal material layer preferably has positive dielectric anisotropy. In addition, the polarizer may further include a polarizing plate attached to the outside of the first substrate and the second substrate, respectively, and the transmission axes of the polarizing plates may be disposed perpendicularly or horizontally to each other.

In such a liquid crystal display, the liquid crystal molecules are arranged radially with respect to the protrusions with respect to the first and second substrate surfaces.

Here, the liquid crystal material layer may include a chiral additive to return the liquid crystal molecules in a uniform direction by the electric field.

In another embodiment of the present invention, the liquid crystal display device includes first and second substrates facing each other, and between the first and second substrates, the first and second substrates extending from the first substrate to the second substrate. A liquid crystal material layer is injected that includes a hybrid array in which the inclination angle of the liquid crystal molecules with respect to the substrate is gradually increased. In addition, an upper surface of the first and second substrates facing each other has an inclined surface, and protrusions for arranging liquid crystal molecules in a radial or concentric shape are formed with respect to the first and second substrate surfaces.

Here, the liquid crystal material layer preferably has a positive dielectric anisotropy, and the liquid crystal molecules adjacent to the first substrate are arranged along the inclined plane of the protrusion or parallel to the substrate along the concentric circle of the protrusion, and the liquid crystal adjacent to the second substrate. The molecules are arranged perpendicular to the first substrate and the second substrate.

The liquid crystal display further includes first and second alignment layers for aligning liquid crystal molecules horizontally and vertically to each of the first and second substrates facing each other.

Then, the liquid crystal display according to an exemplary embodiment of the present invention and a manufacturing method thereof will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention.

First, the structure of the liquid crystal display according to the first exemplary embodiment of the present invention having the bending arrangement structure in which the liquid crystal molecules are symmetrically arranged with respect to the center plane of the two substrates by the projections will be described.

1A and 1B schematically illustrate the structure and driving principle of a liquid crystal display device having a bending arrangement according to a first embodiment of the present invention, in which FIG. 1A is a cross-sectional view after applying a voltage, and FIG. This is a plan view seen from the top or the bottom of the substrate.

First, as shown in FIGS. 1A and 1B, a liquid crystal display device having a bend arrangement by protrusions includes upper and lower substrates 11 and 12 facing each other, and each of the substrates 11 and 12 may be formed of a liquid crystal display device. On the inner surface, an electric field is generated to drive the liquid crystal molecules 31, and electrodes 41 and 42 made of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO) or an opaque conductive material are respectively formed. Formed. On top of each of the electrodes 41 and 42, the projections 51 and 52 are formed at positions corresponding to each other, and the alignment layers 21 to cover the projections 51 and 52 on the electrodes 41 and 42, respectively. 22) is formed. At this time, the protrusions 51 and 52 may be arranged at any interval, and the protrusions 51 and 52 may be arranged continuously. Here, the alignment films 21 and 22 are horizontal alignment films that can align the liquid crystal molecules 31 almost horizontally with respect to the substrate. The nematic liquid crystal material layer 32 having positive dielectric anisotropy is injected between the alignment layers 21 and 22 of the two substrates 11 and 12. In this case, the liquid crystal molecules 31 directly on the upper and lower alignment layers 21 and 22 are formed due to the inclination angle θ formed between the inclined surfaces 501 and 502 of the protrusions 51 and 52 and the surfaces of the substrates 11 and 12. Each has a certain pretilt angle with respect to the surfaces of the substrates 11 and 12. Here, unlike the embodiment of the present invention, the alignment layers 21 and 22 may be formed below the protrusions 51 and 52, respectively, and the protrusions 51 and 52 may be formed below the electrodes 41 and 42. It may be. In addition, the alignment layers 21 and 22 may not be aligned as in the first embodiment of the present invention, and the protrusions 51 may be formed to make the bending arrangement of the liquid crystal molecules 31 in consideration of the viewing angle in any direction. 52) Each of the inclined surfaces 501 and 502 may be formed in different orientations in the vertex direction of the projections 51 and 52, and the orientation processing directions may be formed in opposite directions to each other. This will be described with reference to FIG. 2. In addition, the shapes of the protrusions 51 and 52 may be formed radially, and may be formed of a polyhedron having a cone or an edge. Although not shown in the drawings, two polarizing plates for polarizing light passing through each of the transparent substrates 11 and 12 may be attached to each other, and the polarizing plates are preferably arranged in parallel with each other in the direction of the light transmission axis. It may be arranged vertically.

In addition, as shown in FIG. 1A, the liquid crystal molecules 31 may return in any direction, and the liquid crystal material layer 32 may include a chiral additive so that the liquid crystal molecules 31 may return in a uniform direction. Can be.

When a driving voltage is applied, as shown in FIG. 1A, the liquid crystal molecules 31 of the liquid crystal material layer 32 adjacent to the upper and lower alignment layers 21 and 22 may have properties or alignment forces of the horizontal alignment layers 21 and 22. Due to the inclination angle (θ) of the projections (51, 52) are arranged with an arbitrary angle with respect to the upper and lower substrate (11, 12) plane, the liquid crystal molecules 31 toward the center plane of the two substrate (11, 12) They are continuously changed under the influence of the orientation force and the electric field perpendicular to the substrates 11 and 12 to have a bending arrangement. At this time, as shown in Figure 2, two regions are arranged symmetrically with respect to the center plane (B) of the two substrates (11, 12) and at the same time symmetrical with respect to the center line (A) between the projections (51, 52) Two areas are created, arranged as Therefore, as shown in FIG. 1A, the viewing angle is widened because the phase retardation of light passing through the liquid crystal material layer 32 is compensated vertically and horizontally.

In addition, as shown in FIG. 1B, when viewed from above the substrates 11 and 12, the liquid crystal molecules 31 are radially arranged to obtain a wide viewing angle and a uniform viewing angle.

In this case, the light passing through the lower substrate 12, the liquid crystal layer 32, and the upper substrate 11 changes in polarization direction due to a difference in phase delay. Here, if the dielectric anisotropy and cell spacing are adjusted to change the polarization direction of the light by about 90 °, the light may pass through a polarizing plate arranged to have a vertical transmission axis in a state where the polarization direction is changed to realize a white state.

In general, the lower electrode 42 of the two electrodes 41 and 42 is a pixel electrode for applying a different data signal for each unit pixel, and the second electrode 41 is a common for applying a signal common to all the pixels. Electrode. In addition, each pixel electrode is connected to one terminal of a switching element such as a thin film transistor formed in each pixel.

In the liquid crystal display device according to the first embodiment of the present invention, unlike the conventional OCB type liquid crystal display device, by using the projections 51 and 52 to obtain the bending arrangement, it is not necessary to apply a high voltage at the initial stage and is stable. A bend array can be obtained.

Of course, in order to display a dark state, a voltage of sufficient magnitude is applied to the two electrodes 41 and 42 so that most of the liquid crystal molecules 31 are vertically aligned with respect to the two substrates 11 and 12. Do not do it. However, in the portions adjacent to the upper and lower alignment layers 21 and 22, since the alignment force of the alignment layers 21 and 22 is stronger than the force due to the applied electric field, the liquid crystal molecules 31 have a pretilt angle θ at this portion. Try to keep the original state arranged.

Next, the structure of the liquid crystal display according to the second exemplary embodiment of the present invention, which has been subjected to an alignment process in an arbitrary direction, will be described in detail with reference to FIG. 2.

 2 is a cross-sectional view schematically illustrating a structure of a liquid crystal display according to a second exemplary embodiment of the present invention.

As shown in Fig. 2, most structures are similar to the first embodiment.

However, the projections 51 and 52 are formed adjacent to each other, and the first projection surface 501 of the projections 51 and 52 is aligned in the alignment treatment direction 1 such that the liquid crystal molecules 31 have a pretilt angle. The projection surface 502 is oriented in the orientation processing direction 2 which is the direction opposite to the orientation processing direction 1.

At this time, the liquid crystal molecules 31 are arranged symmetrically with respect to the center line A between the projections 51 and 52 and the center plane B between the two substrates 11 and 12, and thus have the same effect as in the first embodiment. Has

Here, in order to form the alignment treatment directions 1 and 2, a photoalignment method using rubbing or ultraviolet rays may be used.

Next, the structure and driving principle of the hybrid array will be described with reference to the drawings.

3A and 3B schematically illustrate the structure and driving principle of a liquid crystal display having a hybrid arrangement according to a third exemplary embodiment of the present invention, and show before and after applying a voltage, respectively.

First, as shown in FIGS. 3A and 3B, the liquid crystal display having a hybrid array includes upper and lower substrates 11 and 12 facing each other, and an alignment layer 21 on an inner surface of each of the substrates 11 and 12. And 22 are formed, and electrodes 41 and 42 for generating an electric field for driving the liquid crystal molecules 31 are formed between the substrates 11 and 12 and the alignment layers 21 and 22, respectively. . The alignment layer 21 applied to the upper substrate 11 is a vertical alignment layer that can align the liquid crystal molecules 31 perpendicularly to the substrate, and the alignment layer 22 formed on the lower substrate 12 is the upper substrate. Unlike the alignment film 21 of (11), the liquid crystal molecules 31 can be oriented horizontally with respect to the substrate. The nematic liquid crystal material layer 32 having positive dielectric anisotropy is injected between the alignment layers 21 and 22 of the two substrates 11 and 12.

As shown in FIG. 3A, in the state in which no voltage is applied, the liquid crystal molecules 31 of the liquid crystal material layer 32 adjacent to the upper alignment layer 21 are arranged in a direction substantially perpendicular to the substrate 11, but the lower alignment layer is not. Liquid crystal molecules 31 of the liquid crystal material layer 32 adjacent to 22 are arranged substantially parallel to the substrate 12. Therefore, the liquid crystal molecules 31 form a hybrid arrangement in which the inclination angle with respect to the straight line perpendicular to the substrates 11 and 12 increases as the lower substrate 12 moves toward the upper substrate 11.

Here, the liquid crystal molecules 31 directly on the upper and lower alignment layers 21 and 22 surfaces may have perpendicularity to the substrates 11 and 12 and a predetermined angle of inclination with respect to the surface of the substrates 11 and 12, respectively. have. In addition, although a vertical alignment layer was formed on the upper substrate 11 and a horizontal alignment layer was formed on the lower substrate 12, a horizontal alignment layer was applied to the upper substrate 11 and a vertical alignment layer was applied to the lower substrate 12. You may.

Next, as shown in FIG. 3B, when a voltage having a sufficient magnitude is applied to the two electrodes 41 and 42, an electric field perpendicular to the substrates 11 and 12 is formed, and the nematic liquid crystal molecules 31 having positive dielectric anisotropy are present. ) Are arranged perpendicular to the two substrates 11 and 12 because they are arranged side by side by the electric field. However, in the portions adjacent to the two alignment layers 21 and 22, the alignment force of the alignment layers 21 and 22 is stronger than the force due to the applied electric field, so that the liquid crystal molecules 31 near the lower substrate 12 are horizontal even when a voltage is applied. Maintain the original arrangement.

In the liquid crystal display having such a structure, since a large portion of the liquid crystal molecules are vertically arranged with respect to the substrates 11 and 12 even in an initial state, the speed at which the liquid crystal molecules 31 become perpendicular to the substrate when voltage is applied is high, and the voltage is high. This disappears and is also fast to return to its original state. Therefore, the response speed of the liquid crystal display device is fast. In order to improve the viewing angle of the liquid crystal display, protrusions are formed on the upper or lower substrates 11 and 12 and will be described in detail with reference to the accompanying drawings.

4A and 4B schematically illustrate the structure of a liquid crystal display device having a hybrid arrangement according to a third embodiment of the present invention. FIG. 4A is a cross-sectional view of the substrate surface, and FIG. 4B is an upper portion of the substrate. This is a plan view from above.

As shown in FIGS. 4A and 4B, as shown in FIGS. 3A and 3B, the liquid crystal molecules 31 form a hybrid array from the upper substrate 11 to the lower substrate 12.

However, unlike FIGS. 3A and 3B, protrusions 51 are formed on the upper substrate 11. Accordingly, the liquid crystal molecules 51 lie on the projection surface 501 with the inclination angle θ along the inclination and form a hybrid arrangement to the lower substrate 12. As shown in FIG. 4B, the substrate 11, 12) As viewed from the top, the liquid crystal molecules 31 are arranged in a radial shape. Therefore, since the phase retardation of light passing through the liquid crystal material layer 32 is uniformly formed by the liquid crystal molecules 31 arranged in a radial manner, a wide viewing angle may be obtained.

5A and 5B schematically illustrate the structure of a liquid crystal display device having a hybrid arrangement according to a fourth embodiment of the present invention. FIG. 5A is a cross-sectional view of the substrate surface, and FIG. 5B is an upper portion of the substrate. This is a plan view from above.

As shown in FIGS. 5A and 5B, as shown in FIGS. 3A and 3B, the liquid crystal molecules 31 form a hybrid array from the upper substrate 11 to the lower substrate 12, and are illustrated in FIGS. 4A and 4B. As described above, the projection 51 of the upper substrate 11 is formed.

However, unlike FIGS. 4A and 4B, the liquid crystal molecules 51 lie down the valleys between the protrusions 51 and form a hybrid array to the lower substrate 12. As shown in FIG. 5B, the liquid crystal molecules 51 may be It is arranged in a concentric shape. Accordingly, the phase retardation of light passing through the liquid crystal material layer 32 is uniformly formed by the liquid crystal molecules 31 arranged in concentric circles, thereby obtaining a wide viewing angle.

In addition, in the liquid crystal display according to the exemplary embodiment of the present invention, a linear inclination angle is applied to the liquid crystal molecules by using projections to divide and align them in a radial or concentric shape to obtain a uniform phase delay, thereby rapidly changing the gray level inversion ( gray inversion).

As described above, in the liquid crystal display according to the exemplary embodiment of the present invention, the protrusions are formed to have a pretilt angle to the liquid crystal molecules, and the liquid crystal molecules are bent or hybrid arrayed in a radial or concentric manner to divide the liquid crystal molecules into multiple regions. Orientation allows for a uniform viewing angle in any direction. Gray level inversion can be minimized. In addition, it is possible to have a wide viewing angle by symmetrically compensating for retardation of transmitted light.

Claims (16)

A first substrate comprising a first electrode, A second substrate facing the first substrate, the second substrate including a second electrode forming an electric field with the first electrode; Protrusions formed on the first and second substrates facing each other and having an inclination angle, A first horizontal alignment layer and a second horizontal alignment layer formed on the first substrate and the second substrate, respectively; It is injected between the first and second substrates, and when a driving voltage is applied, the center line and the center line between the protrusions are arranged vertically with respect to the first and second substrates, and at the same time, due to the pretilt angle formed by the protrusions. Liquid crystal material layer composed of liquid crystal molecules arranged symmetrically with respect to the center plane of the substrate Including; The projections on the first substrate and the second substrate are formed at positions facing each other. delete delete The liquid crystal display of claim 1, wherein the first and second alignment layers are aligned in directions facing each other. The liquid crystal display of claim 1, wherein the liquid crystal material layer has positive dielectric anisotropy. The liquid crystal display of claim 1, further comprising a polarizer plate attached to an outer side of the first substrate and the second substrate, respectively. The liquid crystal display of claim 6, wherein the transmission axes of the polarizing plates are disposed to be perpendicular or horizontal to each other. The liquid crystal display of claim 1, wherein, after the driving voltage is applied, the liquid crystal molecules are radially arranged with respect to the protrusions with respect to the first and second substrate surfaces. The liquid crystal display of claim 1, wherein the liquid crystal material layer includes a chiral additive to return the liquid crystal molecules in a uniform direction by the electric field. The liquid crystal display of claim 1, wherein the first or second electrode is made of ITO or IZO, which is an opaque conductive material or a transparent conductive material. First and second substrates facing each other, A liquid crystal material layer implanted between the first and second substrates and including a hybrid arrangement in which the inclination angle of the liquid crystal molecules with respect to the first and second substrates gradually increases from the first substrate to the second substrate , A first alignment layer formed on the first substrate and aligning the liquid crystal molecules horizontally; A second alignment layer formed on the second substrate and vertically aligning the liquid crystal molecules; and It is formed with an inclined surface on the upper side of the first substrate facing, a projection for arranging the liquid crystal molecules in a radial or concentric shape with respect to the first and second substrate surface when a driving voltage is applied Including; And a plurality of projections in one pixel. The liquid crystal display of claim 11, wherein the liquid crystal material layer has positive dielectric anisotropy. The liquid crystal display of claim 11, wherein the liquid crystal molecules adjacent to the first substrate are arranged along the inclined surface of the protrusion. The liquid crystal display of claim 11, wherein, when the driving voltage is applied, the liquid crystal molecules adjacent to the first substrate are arranged parallel to the substrate along a concentric circle of the protrusion. The liquid crystal display of claim 11, wherein the liquid crystal molecules adjacent to the second substrate are arranged perpendicularly to the first substrate and the second substrate after the driving voltage is applied. delete

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