KR101738328B1 - Display panel and multi domain liquid crystal display including the same - Google Patents

Abstract

According to the embodiment of the present invention, the horizontal alignment film and the vertical alignment film can be laminated and aligned on the substrate. Thereby, it is possible to provide a stable multi-domain twisted nematic mode liquid crystal display device having an excellent viewing angle in all gray levels

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display panel for a liquid crystal display device and a multi-domain liquid crystal display device including the same,

The present invention relates to a display panel for a liquid crystal display device and a multi-domain liquid crystal display device including the same.

Among the liquid crystal display devices, in the TN (Twisted Nematic) mode, the liquid crystal display device has higher light transmittance efficiency than the liquid crystal display devices of other modes, and the manufacturing process is simple and most widely used. However, there is a problem that the viewing angle decreases in a specific direction.

In a TN (Twisted Nematic) mode liquid crystal display device, a method of using a retardation film and a method of applying multiple orientations using a horizontal alignment film are known as methods for improving the viewing angle. However, in the case of using a retardation film, an additional process is required and the product unit price is increased. In addition, in the method of applying multiple orientations using a horizontal alignment film, there is a problem that a pre-scan yarn is not sufficiently high, so that a multi-domain can not be formed at a low gray level.

Further, when multiple orientations are applied using a vertical alignment film, the domain stability is high and the response speed is fast because the linear alignment is high from the beginning. Further, since it is in the normally black mode, the transmittance can be high. However, when a multi-domain TN (Twisted Nematic) mode liquid crystal display device is implemented with a vertical alignment layer, the horizontal anchoring energy applied to the liquid crystal layer is reduced, which makes it difficult to maintain the twisted nematic mode.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is an object of the present invention to provide a multi-domain liquid crystal display device having a wobbly nematic mode having a high viewing angle and a fast response speed even at a low gray level.

A liquid crystal display device according to an embodiment of the present invention includes a first substrate, a first horizontal alignment film disposed on the first substrate, a first vertical alignment film disposed on the first horizontal alignment film, A second horizontal alignment film disposed on the second substrate, a second vertical alignment film disposed on the second horizontal alignment film, and a second vertical alignment film disposed between the first substrate and the second substrate, wherein the twisted nematic Mode liquid crystal layer.

Wherein the first horizontal alignment film includes a first region and a second region that are rubbed in directions opposite to each other, and the second horizontal alignment film includes a third region and a fourth region that are rubbed in directions opposite to each other, The rubbing direction of the first region and the second region and the rubbing direction of the third region and the fourth region may be perpendicular to each other.

The liquid crystal molecules of the liquid crystal layer may have positive dielectric anisotropy.

The liquid crystal molecules of the liquid crystal layer may have a negative dielectric anisotropy.

According to another aspect of the present invention, there is provided a liquid crystal display comprising a first substrate, a first alignment layer disposed on the first substrate and including a horizontal alignment layer and a vertical alignment layer, a second substrate facing the first substrate, A second alignment layer disposed on the second substrate and including a horizontal alignment layer and a vertical alignment layer and a liquid crystal layer injected between the first and second substrates in a twisted nematic mode.

According to an embodiment of the present invention, liquid crystal molecules can be aligned by using an alignment film including a horizontal alignment material and a vertical alignment material. Thereby, a multi-domain liquid crystal display device having an excellent viewing angle even at a low gradation can be provided. According to an embodiment of the present invention, by orienting liquid crystal molecules using an alignment layer including a horizontal alignment material and a vertical alignment material, a combination of horizontal anchoring energy and vertical anchoring energy applied to the liquid crystal layer, A twisted nematic mode liquid crystal display device can be provided.

1A is a cross-sectional view showing a display panel for a liquid crystal display device according to an embodiment of the present invention.
1B is a cross-sectional view illustrating a liquid crystal display device according to an embodiment of the present invention.
2A is a cross-sectional view illustrating a display panel for a liquid crystal display according to another embodiment of the present invention.
2B is a cross-sectional view illustrating a liquid crystal display device according to another embodiment of the present invention.
3A is a cross-sectional view illustrating a display panel for a liquid crystal display device according to another embodiment of the present invention.
3B is a cross-sectional view illustrating a liquid crystal display device according to another embodiment of the present invention.
4A and 4B are conceptual views illustrating a method of forming multiple domains in a liquid crystal display according to an embodiment of the present invention.
5 is a graph showing the results of the pre-alignment of the dual orientation film of the liquid crystal display device according to one experimental example of the present invention.
6 is a graph showing a result of domain stability evaluation of a liquid crystal display device according to an experimental example of the present invention.
FIGS. 7A and 7B are graphs showing display characteristic results of a liquid crystal display device according to one experimental example of the present invention, and show the results of measurement of viewing angle.
7 (c) and 7 (d) are graphs showing display characteristic results of a liquid crystal display device according to one experimental example of the present invention, and show gray scale inversion results.
8A to 8C are graphs showing response speed results of a liquid crystal display according to an experimental example of the present invention.
9 is a cross-sectional view of a liquid crystal display device according to another embodiment of the present invention.
10 is a cross-sectional view of a liquid crystal display device according to another embodiment of the present invention.
11A to 11C are graphs showing the domain stability evaluation results of the liquid crystal display device according to one experimental example of the present invention.
12 is a graph showing the results of implementation of a multi-domain liquid crystal display device according to an alignment film condition of a liquid crystal display device according to an experimental example of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Is provided to fully convey the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims.

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

First, a display panel for a liquid crystal display according to an embodiment of the present invention will be described with reference to FIG. 1A. 1A is a cross-sectional view showing a display panel for a liquid crystal display device according to an embodiment of the present invention.

1A, a display panel for a liquid crystal display according to an exemplary embodiment of the present invention includes an insulating substrate 110, a horizontal alignment layer 120 disposed on the insulating substrate 110, And a vertical alignment film 130.

Here, the alignment layer may include any one of poly-amic acid, polyimide, nylon, PVA (polyvinylalcohol, PVC), and the alignment layer may include a photo alignment material Photoinduced materials can be classified into photodegradation materials, photoisomerization materials, photo-curing materials and photopolymerization materials depending on the kind of reaction to light. In the case of photodegradation materials, the polymer chain is decomposed by polarized UV For example, when polyimide is irradiated with polarized UV light, the chain is broken and oxidation reaction is accompanied. The above materials are highly thermally stable Stability can be obtained.

The photoisomerization material changes into cis / trans isomer by light and is optically oriented in the direction generated by it.

The photo-curing material is photo-aligned by selectively reacting and having anisotropy in the light reactors oriented in the polarization direction by the polarized UV.

The photopolymerizable material is photopolymerized upon light irradiation to form a polymer having a linear gradient.

Here, the photo alignment material may be at least one selected from the group consisting of polyimide, polyamic acid, polynorbornene, phenylmaleimide copolymer, polyvinylcinnamate, polyazobenzene, polyethyleneimine, Polyvinyl alcohol, polyamide, polyethylene, polystylene, polyphenylenephthalamide, polyester, polyurethane, polysiloxanecinnamate in polysiloxane, , A cellulosecinnamate-based compound, and a polymethyl methacrylate-based compound.

It is possible to stack the horizontal alignment film 120 on the substrate 110 and then stack the vertical alignment film 130 on the substrate 110 without aligning the alignment film 120. Alternatively, after the horizontal alignment film 120 is stacked on the substrate 110, And then the vertical alignment film 130 may be laminated thereon.

The orientation film 130 may be oriented to have a plurality of domains, and the orientation may be performed by rubbing or photo alignment. [0070] All the orientation films according to the embodiment of the present invention have a certain line In the present specification, the pre-warp yarns may have an angle and a direction, and hereinafter referred to as a polar angle (0-90) and an azimuthal angle (azimuthal angle) , 0-360). That is, the pre-warp yarns can be interpreted to include both the azimuthal angle (0-360) and the polar angle (0- + 90). Here, the azimuth angle refers to an angle at which the projection of the alignment film or the liquid crystal onto the substrate surface is inclined with respect to the signal line, for example, the gate line or the data line of the liquid crystal display device. The polar angle means the angle at which the orientation control agent or liquid crystal is tilted with respect to the horizontal plane of the substrate.

The vertical alignment layer 130 is formed by mixing a vertical alignment material with a solvent (NMP, BL, BC, etc.). The thickness of the vertical alignment 130 varies depending on the content of the vertical alignment film material (capacity percentage: wt%).

Since the vertical alignment layer 130 is applied after the horizontal alignment layer 120 is applied, the anchoring energy of the two alignment layers 120 and 130 A line inclination having an intermediate value between the horizontal alignment film 120 and the vertical alignment film 130 can be realized. For example, when the thickness of the vertical alignment film 130 is increased as compared with the horizontal alignment film 120, the diameter of the pre-alignment film becomes large, and in the opposite case, the pre-alignment film can be made small.

Therefore, in the case of the display panel for a liquid crystal display device according to the embodiment of the present invention, the liquid crystal molecules can be oriented so as to have a desired line inclination because of the double orientation film, which is a laminated structure of the horizontal orientation film and the vertical orientation film.

Hereinafter, a liquid crystal display device according to an embodiment of the present invention will be described with reference to FIG. 1B is a cross-sectional view illustrating a liquid crystal display device according to an embodiment of the present invention.

Referring to FIG. 1B, the liquid crystal display according to the present embodiment includes two opposing display panels 100 and 200 and a liquid crystal layer 3 interposed therebetween.

The lower panel 100 includes a first horizontal alignment layer 120 disposed on the first insulating substrate 110 and a first vertical alignment layer 130 disposed on the first horizontal alignment layer 120

The upper display panel 200 includes a second horizontal alignment layer 220 disposed on the second insulating substrate 210 and a second vertical alignment layer 230 disposed on the second horizontal alignment layer 220.

Although not shown, a switching element, for example, a thin film transistor (TFT) connected to a signal line such as a gate line or a data line and a signal line, and a pixel electrode connected to the switching element are formed on the insulating substrate 110 . A color filter, a light shielding member, a common electrode, and the like may be formed on the insulating substrate 110.

The first horizontal alignment layer 120 and the first vertical alignment layer 130 of the lower panel 100 include at least two first regions and second regions oriented in different directions, 2 The horizontal alignment film 220 and the second vertical alignment film 230 include at least two third regions and fourth regions that are oriented in different directions.

The first and second regions of the first horizontal alignment layer 120 and the first vertical alignment layer 130 of the lower panel 100 may be oriented in opposite directions to each other and the second horizontal alignment layer 220 and the third and fourth regions of the second vertical alignment film 230 may be oriented in directions opposite to each other.

The alignment direction of the first region and the second region of the lower panel 100 may be perpendicular to the alignment of the third region and the fourth region of the upper panel 200.

The first horizontal alignment film 120 may be laminated on the first substrate 110 of the lower panel 100 and then the first vertical alignment film 130 may be laminated thereon without orientation, The first horizontal alignment layer 120 may be stacked on the first vertical alignment layer 130, and then the first vertical alignment layer 130 may be stacked on the first horizontal alignment layer 120 in a desired direction.

The second horizontal alignment layer 220 and the second vertical alignment layer 230 of the upper panel 200 may be similarly formed by stacking the second horizontal alignment layer 220 on the second substrate 210 and then aligning The second vertical alignment film 230 may be laminated or the second horizontal alignment film 220 may be laminated on the second substrate 210 and then oriented in a desired direction and then a second vertical alignment film 230 may be formed thereon Or may be laminated.

In the illustrated embodiment, both the lower panel 100 and the upper panel 200 include a horizontal alignment film and a vertical alignment film. However, since at least one of the two display panels 100 and 200 has a laminated structure of a horizontal alignment film and a vertical alignment film And may include an alignment film.

Although not shown, the first substrate 110 or the second substrate 210 is connected to a switching element, for example, a thin film transistor (TFT), and a switching element, which are connected to signal lines such as a gate line and a data line, A color filter, a light shielding member, a common electrode, and the like may be formed.

In general, in a horizontally aligned twisted nematic liquid crystal display device, the minimum polar angle (? _Min ) of a pre-warp yarn required to form four stable domains is obtained by the following equation.

θ _min ² = π × d / L

Where d is the cell spacing of the liquid crystal layer and L is the horizontal dimension of the domain.

For example, if the cell spacing is 5 [mu] m and the horizontal size of the domain is 100 [mu] m, then the minimum pole angle [theta] _min required to form the stable four domains is about 22 degrees.

Generally, it is difficult to form four stable domains in the TN mode because the horizontal alignment film has a polar angle of about 4-5 degrees and the vertical alignment film has a polar angle of about 89-90 degrees.

Since the vertical alignment layer 130 is applied after the horizontal alignment layer 120 is applied, the anchoring energy of the two alignment layers 120 and 130 It is possible to realize a line inclination having a value of an intermediate region between the horizontal alignment film 120 and the vertical alignment film 130 by combination. Particularly, in the horizontally oriented twisted nematic liquid crystal display device as in the embodiment of the present invention, azimuthal angle is determined by rubbing or photo alignment, and the polar angle can be controlled by the double alignment film. For example, when the thickness of the vertical alignment film 130 is increased as compared with the horizontal alignment film 120, the polar angle increases, and conversely, the polar angle decreases.

Therefore, in the case of the display panel for a liquid crystal display device according to the embodiment of the present invention, the liquid crystal molecules can be oriented so as to have a desired polar angle, because it is a dual orientation film which is a laminated structure of a horizontal orientation film and a vertical orientation film.

Hereinafter, a display panel and a liquid crystal display for a liquid crystal display according to another embodiment of the present invention will be described with reference to FIGS. 2A and 2B. FIG. FIG. 2A is a cross-sectional view showing a display panel for a liquid crystal display according to an embodiment of the present invention, and FIG. 2B is a cross-sectional view illustrating a liquid crystal display according to an embodiment of the present invention.

2A, a display panel for a liquid crystal display according to an embodiment of the present invention includes an insulating substrate 110, a mixed alignment layer 140 including a horizontal alignment material and a vertical alignment material, ). The mixed alignment layer 140 may be formed by mixing a horizontal alignment material and a vertical alignment material.

Here, the alignment material may include any one of poly-amic acid, poly-imide, nylon, PVA (polyvinylalcohol, PVC), and the alignment layer may be a photo- Photoinduced materials can be divided into photodegradation materials, photoisomerization materials, photo-curing materials and photopolymerization materials depending on the kind of reaction to light. In the case of photodegradation materials, the decomposition of polymer chains by polarized UV Can be optically aligned using the structural anisotropy produced thereby, for example, when polyimide is irradiated with polarized UV, the chain is broken and oxidation reaction is accompanied. And may have thermal stability.

The photoisomerization material changes into cis / trans isomer by light and is optically oriented in the direction generated by it.

The photo-curing material is photo-aligned by selectively reacting and having anisotropy in the light reactors oriented in the polarization direction by the polarized UV.

The photopolymerizable material is photopolymerized upon light irradiation to form a polymer having a linear gradient.

Herein, the photo-alignment material may be at least one selected from the group consisting of polyimide, polyamic acid, polynorbornene, phenylmaleimide copolymer, polyvinylcinnamate, polyazobenzene, polyethyleneimine, ), Polyvinyl alcohol, polyamide, polyethylene, polystylene, polyphenylenephthalamide, polyester, polyurethane, polysiloxane, and the like. A polymeric material selected from the group consisting of Polysiloxanecinnamate, Cellulosecinnamate-based compounds and Polymethyl methacrylate-based compounds.

The mixed alignment layer 140 is formed by mixing a vertical alignment material with a solvent (NMP: BL: BC) and mixing the same with the horizontal alignment layer. The polar angle of the mixed alignment layer 140 is changed according to the content of the vertical alignment layer material (capacity percentage: wt%).

As described above, since the horizontal alignment film has a polar angle of about 4-5 ° and the vertical alignment film has a polar angle of about 89-90 °, four stable domains (twisted nematic) in a horizontally oriented twisted nematic (TN) .

In the case of the display panel for a liquid crystal display according to the embodiment of the present invention, since the alignment is performed using the mixing alignment layer 140 in which the horizontal alignment material and the vertical alignment material are mixed, anchoring energy ), It is possible to realize a line inclination having a value of an intermediate region between the horizontal alignment material and the vertical alignment material. As described above, the line inclination (polar angle) can be changed depending on the content of the vertical alignment film material added to the solvent. Therefore, in the case of the display panel for a liquid crystal display device according to the embodiment of the present invention, the liquid crystal molecules can be oriented so as to have a desired polar angle because the mixed alignment layer is a mixture of the horizontal alignment film and the vertical alignment film.

2B, a liquid crystal display device according to an embodiment of the present invention will be described.

Referring to FIG. 2B, the liquid crystal display according to the present embodiment includes two display panels 100 and 200 facing each other and a liquid crystal layer 3 injected therebetween.

The lower panel 100 includes a first insulating alignment layer 140 disposed on the first insulating substrate 110 and the first insulating substrate 110 and including a horizontal alignment material and a vertical alignment material.

The upper display panel 200 includes a second mixing orientation layer 240 disposed on the second insulating substrate 210 and the second insulating substrate 210 and including a horizontal alignment material and a vertical alignment material. The second mixed alignment layer 240 may include at least one of PI, a photo alignment layer, nylon, PVC, and PVA.

The first mixing orientation layer 140 of the lower panel 100 includes at least two first regions and a second region rubbed in different directions and the second mixing orientation layer 240 of the upper panel 200 includes And at least two third regions and fourth regions rubbed in different directions.

The first area and the second area of the first mixing alignment layer 140 of the lower panel 100 may be rubbed in opposite directions and the third area of the second mixing alignment layer 240 of the upper panel 200 4 regions can be rubbed in directions opposite to each other.

The rubbing direction of the first region and the second region of the lower panel 100 and the rubbing direction of the third region and the fourth region of the upper panel 200 may be perpendicular to each other.

In the illustrated embodiment, both the lower panel 100 and the upper panel 200 include mixed alignment layers. However, at least one of the two panels 100 and 200 may include a mixed alignment layer. Although not shown, in another embodiment of the present invention, at least one of the mixed alignment layers 140 and 240 may include an orientation control agent.

Although not shown, the first substrate 110 or the second substrate 210 is connected to a switching element, for example, a thin film transistor (TFT), and a switching element, which are connected to signal lines such as a gate line and a data line, A color filter, a light shielding member, a common electrode, and the like may be formed.

Next, a display panel for a liquid crystal display according to another embodiment of the present invention will be described with reference to FIG. 3A. 3A is a cross-sectional view illustrating a display panel for a liquid crystal display device according to another embodiment of the present invention.

Referring to FIG. 3A, the display panel for a liquid crystal display device according to the present embodiment is similar in lamination structure to the display panel shown in FIG. 1A. A horizontal alignment film 120 disposed on the insulating substrate 110; and a vertical alignment film 130 disposed on the horizontal alignment film 120.

However, unlike the embodiment shown in FIG. 1A, the alignment layer 20 further includes an alignment layer in a laminated structure of the horizontal alignment layer 120 and the vertical alignment layer 130. The orientation control agent 20 may further include an orientation control agent 20 in an orientation layer of a laminated structure of the horizontal orientation film 120 and the vertical orientation film 130. Herein, the orientation control agent refers to a polymerized photopolymerizable monomer or oligomer, For example, reactive mesogens, NOA series (Norland), and the like.

Reactive mesogens are materials that are polymerized by light, such as ultraviolet light, and are oriented according to the orientation of adjacent materials. Here, the adjacent materials can use the liquid crystal 300 as described above. Examples of the reactive mesogens include compounds represented by the following formulas.

P1-A1- (Z1-A2) n-P2,

Here, P1 and P2 are independently selected from the group consisting of acrylate, methacrylate, vinyl, vinyloxy and epoxy, and A1 and A2 are 1,4- Phenylen and naphthalene-2,6-diyl group, Z1 is one of COO-, OCO- and a single bond, and n is one of 0, 1 and 2 .

More specifically, there can be mentioned a compound represented by one of the following formulas:

Here, P1 and P2 are independently selected from the group consisting of acrylate, methacrylate, vinyl, vinyloxy and epoxy groups.

   In this embodiment, the alignment layer 130 may be formed by mixing an alignment control material with the alignment material. At this time, a polymerization initiator may be added. The polymerization initiator does not necessarily have to be added, but the polymerization can be rapidly promoted by adding a polymerization initiator. Examples of the polymerization initiator include, in addition to methyl ethyl ketone peroxide, benzoyl peroxide, cumene hydroperoxide, t-butyl peroctoate, dicumyl peroxide, benzoyl alkyl ether, acetophenone, A xanthene benzoin ether-based polymerization initiator, and a benzyl ketal polymerization initiator. These polymerization initiators can be used as they are, or they can be used as appropriate.

After forming an alignment film using a mixed material, ultraviolet rays are irradiated to polymerize the alignment control material to form an orientation control agent 20, or a liquid crystal layer is formed. Then, a voltage is applied between both substrates to change the line inclination of the liquid crystal director The orientation adjusting material 20 may be formed by polymerizing the alignment controlling material by irradiating ultraviolet rays while the liquid crystal director is in a state of being aligned. Thus, the response speed of the liquid crystal layer can be improved.

In this embodiment, the horizontal alignment film 120 may be laminated on the substrate 110, and then the vertical alignment film 130 may be laminated on the substrate 110 without orientation, or the horizontal alignment film 120 may be laminated on the substrate 110 The alignment layer 130 may be aligned on the alignment layer 130 in a predetermined direction.

The liquid crystal display according to another embodiment of the present invention will now be described with reference to FIG. 3B. 3B is a cross-sectional view illustrating a liquid crystal display device according to another embodiment of the present invention.

Referring to FIG. 3B, the liquid crystal display according to the present embodiment is similar to the liquid crystal display shown in FIG. 1B. The liquid crystal display according to the present embodiment includes two display plates 100 and 200 facing each other and a liquid crystal layer 3 injected therebetween.

The lower panel 100 includes a first horizontal alignment layer 120 disposed on the first insulating substrate 110 and a first vertical alignment layer 130 disposed on the first horizontal alignment layer 120. The upper display panel 200 includes a second horizontal alignment layer 220 disposed on the second insulating substrate 210 and a second vertical alignment layer 230 disposed on the second horizontal alignment layer 220. However, unlike the embodiment shown in FIG. 1B, the first vertical alignment film 130 further includes the alignment adjuster 20. FIG. By further including the alignment control agent 20 in the first vertical alignment film 130, the response speed can be increased.

In the illustrated embodiment, the alignment control agent 20 is included only in the first vertical alignment layer 130 of the lower panel 100, but the alignment control agent 20 is also applied to the second vertical alignment layer 230 of the upper panel 200 And the alignment control agent 20 may be included in the first horizontal alignment film 120 and the second horizontal alignment film 220 as well.

The first horizontal alignment layer 120 and the first vertical alignment layer 130 of the lower panel 100 include at least two first regions and second regions oriented in different directions, 2 The horizontal alignment film 220 and the second vertical alignment film 230 include at least two third regions and fourth regions that are oriented in different directions.

The first and second regions of the first horizontal alignment layer 120 and the first vertical alignment layer 130 of the lower panel 100 may be oriented in opposite directions to each other and the second horizontal alignment layer 220 and the third and fourth regions of the second vertical alignment film 230 may be oriented in directions opposite to each other.

The alignment direction of the first region and the second region of the lower panel 100 may be perpendicular to the alignment of the third region and the fourth region of the upper panel 200.

The first horizontal alignment film 120 may be laminated on the first substrate 110 of the lower panel 100 and then the first vertical alignment film 130 may be laminated thereon without orientation, The first horizontal alignment layer 120 may be stacked on the first vertical alignment layer 130, and then the first vertical alignment layer 130 may be stacked on the first horizontal alignment layer 120 in a desired direction.

The second horizontal alignment layer 220 and the second vertical alignment layer 230 of the upper panel 200 may be similarly formed by stacking the second horizontal alignment layer 220 on the second substrate 210 and then aligning The second vertical alignment film 230 may be laminated or the second horizontal alignment film 220 may be laminated on the second substrate 210 and then oriented in a desired direction and then a second vertical alignment film 230 may be formed thereon Or may be laminated.

In the illustrated embodiment, both the lower panel 100 and the upper panel 200 include a horizontal alignment film and a vertical alignment film. However, since at least one of the two display panels 100 and 200 has a laminated structure of a horizontal alignment film and a vertical alignment film And may include an alignment film.

As described above, in the liquid crystal display according to the embodiment of the present invention, an alignment film is formed by laminating a vertical alignment film including a horizontal alignment film and an alignment regulator on a substrate, and after orienting the film in a desired direction (rubbing or photo alignment) By irradiating UV light in the applied state, the alignment direction of the liquid crystal director aligned by the alignment film is fixed and aligned so as to have a desired line inclination, and at the same time, the line inclination can be enhanced, The response speed of the liquid crystal molecules of the horizontally aligned twisted nematic liquid crystal display device can be accelerated. Therefore, it is possible to obtain a liquid crystal display device having excellent viewing angles in all gradations, and realize a fast response speed.

4A and 4B, a method of forming multiple domains of a liquid crystal display according to an embodiment of the present invention will be described. 4A and 4B are conceptual views illustrating a method of forming multiple domains in a liquid crystal display according to an embodiment of the present invention. FIG. 4A conceptually shows the rubbing direction of the alignment film structure, and FIG. 4B conceptually shows the arrangement of the liquid crystal director according to the rubbing of FIG. 4A.

In FIG. 4A, a represents the rubbing direction of the lower panel 100, b represents the rubbing direction of the upper panel 200, and c represents the arrangement direction of the liquid crystal director.

4A, the first horizontal alignment layer 120 of the lower panel 100 and the lamination orientation layer of the first vertical alignment layer 130 are aligned in opposite directions to form a first subregion Ra And Rb and the second sub-regions Rc and Rd oriented in the second direction.

The second horizontal alignment film 220 of the upper panel 200 and the laminated orientation film of the second vertical alignment film 230 are oriented in opposite directions to form third subregions Ra and Rc oriented in the third direction, (Rb, Rd) oriented in the direction of the first sub-area (Rb, Rd).

Rb, Rc, Rd (Rd, Rb, Rc, Rd) aligned in different directions are formed by joining the lower panel 100 and the upper panel 200 together, ) Can be formed. As described above, by forming four domains having different alignment directions, the viewing angle can be increased.

As shown in the figure, the alignment direction of the laminated orientation film of the lower panel 100 and the orientation direction of the lamination orientation film of the upper display panel 200 may be perpendicular to each other.

Here, it is described that the alignment film is multi-rubbed, but the alignment film can be oriented by photo alignment. At this time, by irradiating light in a state where a part of the alignment film is masked with the mask, the alignment film can be formed to have multidomain. Further, in the light irradiation step, the azimuth angle and polar angle of each domain can be regulated according to the polarization direction of light and / or the degree of tilting of the substrate.

Referring to FIG. 5, a line inclination result of the dual orientation film of the liquid crystal display device according to one experimental example of the present invention will be described. 5 is a graph showing the results of the pre-alignment of the dual orientation film of the liquid crystal display device according to one experimental example of the present invention.

Referring to FIG. 5, it can be seen that as the content (wt%) of the vertical alignment film is increased in the alignment film of the double film structure of the horizontal alignment film and the vertical alignment film according to the embodiment of the present invention, the polar angle of the linear alignment film increases. Accordingly, it was found that when the alignment film of the double-film structure of the horizontal alignment film and the vertical alignment film according to the embodiment of the present invention is used, the liquid crystal molecules can be oriented so as to have a desired line inclination by controlling the content of the vertical alignment film.

Hereinafter, the domain stability of the liquid crystal display according to one experimental example of the present invention will be described with reference to FIG. 6 is a graph showing a result of domain stability evaluation of a liquid crystal display device according to an experimental example of the present invention. In Fig. 6, solid lines shown in the respective figures indicate domain boundaries. FIG. 6A shows a case where the polar angle is 4 degrees, FIG. 6B shows the case where the polar angle is 7 degrees, and FIG. 6C shows the case where the polar angle is 18 degrees.

6A, when the liquid crystal molecules aligned by the alignment film have a polar angle of 4 DEG, the stability of the four domains is lowered in a range of gradation or lower in which a voltage of about 1.2 V is applied to the liquid crystal layer Referring to FIG. 6 (b), when the liquid crystal molecules have a polar angle of 7 degrees, the stability of the four domains is degraded in the sub-gradation range in which a voltage of about 1.0 V is applied to the liquid crystal layer And it was found. Referring to (c) of FIG. 6, it was confirmed that when the liquid crystal molecules aligned by the alignment film had a polar angle of 18 °, four multiple domains were stably formed even at a low voltage of OV. That is, when the polar angle is 18 degrees or less, multiple domains are not formed at a low voltage. Accordingly, it was found that stable multiple domains can be realized by controlling the polar angle by using a double orientation film or a mixed orientation film having a lamination structure including a horizontal orientation film and a vertical orientation film, like the display panel for a liquid crystal display according to the present embodiment .

Hereinafter, the display characteristics of the liquid crystal display device according to one experimental example of the present invention will be described with reference to FIG. 7 is a graph showing display characteristics of a liquid crystal display device according to an experimental example of the present invention. Figs. 7 (a) and 7 (b) show the results of measurement of viewing angle, and Figs. 7 (c) and 7 (d) show gray scale inversion results.

Referring to FIG. 7, it can be seen that the liquid crystal display according to the embodiment of the present invention has improved viewing angle symmetry as compared with a general TN mode liquid crystal display, and that the gray scale inversion is also improved. As described above, as in the case of the display panel for a liquid crystal display according to the present embodiment, it is possible to obtain an excellent viewing angle and display quality by implementing multiple domains by using a dual alignment film as a lamination structure of a horizontal alignment film and a vertical alignment film there was.

Next, the response speed of the liquid crystal display device according to one experimental example of the present invention will be described with reference to FIG. 8 is a graph showing the response speed results of the liquid crystal display according to one experimental example of the present invention. FIG. 8A shows the rising time of the liquid crystal molecules, FIG. 8B shows the falling time of the liquid crystal molecules, and FIG. 8C shows the total response time of the liquid crystal molecules. 8A to 8C, A is a general twisted nematic (TN) mode liquid crystal display, B is a general multi-domain twisted nematic (TN) mode liquid crystal display , And C is a multi-domain liquid crystal display device according to an embodiment of the present invention.

Referring to FIGS. 8A to 8C, in comparison with a general twisted nematic (TN) mode or a general multi-domain twisted nematic (TN) mode liquid crystal display, In the case of the domain liquid crystal display device, it was found that the response speed was improved.

Next, a liquid crystal display device according to another embodiment of the present invention will be described with reference to FIG. 9 is a cross-sectional view of a liquid crystal display device according to another embodiment of the present invention.

Referring to FIG. 9, the liquid crystal display device according to this embodiment is similar to the liquid crystal display device shown in FIG. 1B.

The liquid crystal display according to the present embodiment includes two display plates 100 and 200 facing each other and a liquid crystal layer 3 injected therebetween.

The lower panel 100 includes a first horizontal alignment layer 120 disposed on the first insulating substrate 110 and a first vertical alignment layer 130 disposed on the first horizontal alignment layer 120. The upper display panel 200 includes a second horizontal alignment layer 220 disposed on the second insulating substrate 210 and a second vertical alignment layer 230 disposed on the second horizontal alignment layer 220.

The first horizontal alignment layer 120 and the first vertical alignment layer 130 of the lower panel 100 include at least two first regions and second regions rubbed in different directions, 2 The horizontal alignment film 220 and the second vertical alignment film 230 include at least two third regions and a fourth region rubbed in different directions.

The first and second regions of the first horizontal alignment layer 120 and the first vertical alignment layer 130 of the lower panel 100 can be rubbed in opposite directions and the second horizontal alignment layer 220 and the third and fourth regions of the second vertical alignment layer 230 may be rubbed in directions opposite to each other.

The rubbing direction of the first region and the second region of the lower panel 100 and the rubbing direction of the third region and the fourth region of the upper panel 200 may be perpendicular to each other.

However, unlike the liquid crystal display device shown in FIG. 1B, the liquid crystal display device according to the present embodiment differs from the liquid crystal display device shown in FIG. 1B in that the polar angles of the liquid crystal molecules 31 disposed in the regions adjacent to the first substrate 110 and the second substrate 210 Is larger. In addition, the liquid crystal molecules in the liquid crystal layer 3 are reverse twisted nematic (reverse TN) modes having negative dielectric anisotropy and twisted to have a constant pitch. Such an inverted twisted nematic mode liquid crystal display device uses a normally black mode and has excellent black display and fast response speed.

Generally, when a twisted nematic mode liquid crystal display device is implemented using a liquid crystal having a negative dielectric constant anisotropy, a liquid crystal is initially vertically aligned using a vertical alignment film. However, when the liquid crystal molecules are initially oriented using the vertical alignment film, the horizontal anchoring energy of the liquid crystal molecules is reduced, and it is difficult to realize a twisted nematic mode liquid crystal display device.

In order to realize a nematic mode in which the liquid crystal layer is reversed, the azimuthal anchoring energy applied to the liquid crystal molecules should be larger than the twist deformation energy expressed by the following equation.

Here, d is the cell spacing of the liquid crystal display, and k is a constant that varies with the liquid crystal material.

When a reverse twisted nematic liquid crystal display using a negative dielectric constant anisotropic liquid crystal layer is aligned only by using a vertical alignment film, the value of horizontal anchoring energy applied to the liquid crystal layer is very small. Therefore, the value of the horizontal anchoring energy becomes smaller than the twist strain energy expressed by the above equation, and the liquid crystal layer can not maintain the reverse twisted nematic mode.

However, in the case of the liquid crystal display device according to the embodiment of the present invention, since the vertical alignment films 130 and 230 are applied after the horizontal alignment films 120 and 220 are applied, the horizontal alignment films 120 and 220 and the vertical alignment films The horizontal anchoring energy applied to the liquid crystal layer 3 by the horizontal alignment film may be larger than the kink strain energy while having a large polar angle by the vertical alignment film due to the combination of the anchoring energies of the liquid crystal layer 3, It is possible to maintain an inverted twisted nematic mode and realize a reversely twisted nematic liquid crystal display having a plurality of domains.

For example, the thickness of the vertical alignment layers 130 and 230 can be adjusted so as to maintain the horizontal anchoring energy by the horizontal alignment layers 120 and 220 applied to the liquid crystal layer 3, and is preferably thinner than about 30 nm .

In order to manufacture an alignment layer of a liquid crystal display device according to an embodiment of the present invention, a first horizontal alignment layer 120 is laminated on a first substrate 110 of a lower panel 100, After the first vertical alignment film 120 is laminated on the first substrate 110, the first vertical alignment film 130 is rubbed in a desired direction, and then the first vertical alignment film 130 is laminated on the first vertical alignment film 130. [ May be laminated.

Similarly to the second horizontal alignment film 220 and the second vertical alignment film 230 of the upper panel 200, after the second horizontal alignment film 220 is laminated on the second substrate 210, The second horizontal alignment film 220 may be laminated on the second substrate 210 and thereafter rubbed in a desired direction and then a second vertical alignment film 220 may be formed on the second horizontal alignment film 220. [ The alignment film 230 may be laminated.

In the illustrated embodiment, both the lower panel 100 and the upper panel 200 include a horizontal alignment film and a vertical alignment film. However, since at least one of the two display panels 100 and 200 has a laminated structure of a horizontal alignment film and a vertical alignment film And may include an alignment film.

10, a liquid crystal display device according to another embodiment of the present invention will be described. 10 is a cross-sectional view of a liquid crystal display device according to another embodiment of the present invention.

Referring to FIG. 10, the liquid crystal display device according to this embodiment is similar to the liquid crystal display device shown in FIG. 2B.

The liquid crystal display according to the present embodiment includes two display plates 100 and 200 facing each other and a liquid crystal layer 3 injected therebetween.

The lower panel 100 includes a first insulating alignment layer 140 disposed on the first insulating substrate 110 and the first insulating substrate 110 and including a horizontal alignment material and a vertical alignment material.

The upper display panel 200 includes a second mixing orientation layer 240 disposed on the second insulating substrate 210 and the second insulating substrate 210 and including a horizontal alignment material and a vertical alignment material. The second mixed alignment layer 240 may include at least one of PI, a photo alignment layer, nylon, PVC, and PVA.

The first mixing orientation layer 140 of the lower panel 100 includes at least two first regions and a second region rubbed in different directions and the second mixing orientation layer 240 of the upper panel 200 includes And at least two third regions and fourth regions rubbed in different directions.

The first area and the second area of the first mixing alignment layer 140 of the lower panel 100 may be rubbed in opposite directions and the third area of the second mixing alignment layer 240 of the upper panel 200 4 regions can be rubbed in directions opposite to each other.

However, unlike the liquid crystal display device shown in FIG. 2B, the liquid crystal display device according to the present embodiment differs from the liquid crystal display device shown in FIG. 2B in that the polar angles of the liquid crystal molecules 31 disposed in the regions adjacent to the first substrate 110 and the second substrate 210 Is larger. In addition, the liquid crystal molecules in the liquid crystal layer 3 are reverse twisted nematic (reverse TN) modes having negative dielectric anisotropy and twisted to have a constant pitch.

The rubbing direction of the first region and the second region of the lower panel 100 and the rubbing direction of the third region and the fourth region of the upper panel 200 may be perpendicular to each other.

Generally, when a twisted nematic mode liquid crystal display device is implemented using a liquid crystal having a negative dielectric constant anisotropy, a liquid crystal is initially vertically aligned using a vertical alignment film. However, when the liquid crystal molecules are initially oriented using the vertical alignment film, the horizontal anchoring energy of the liquid crystal molecules is reduced, and it is difficult to realize a twisted nematic mode liquid crystal display device.

However, since the liquid crystal display according to the embodiment of the present invention is oriented by using the mixing alignment layers 140 and 240 in which the horizontal alignment material and the vertical alignment material are mixed, the anchoring energy of the horizontal alignment film material and the vertical alignment material ), The horizontal anchoring energy applied to the liquid crystal layer 3 by the horizontal alignment material can be larger than the twist strain energy while having a large polar angle by the vertical alignment material, so that the twisted nematic mode can be maintained , A twisted nematic liquid crystal display device having a plurality of domains can be implemented.

Here, the amount of the vertical alignment material can be adjusted so as to maintain the horizontal anchoring energy due to the horizontal alignment material applied to the liquid crystal layer 3, and the thickness of the vertical alignment material layer is preferably about 30 nm or less.

In the illustrated embodiment, both the lower panel 100 and the upper panel 200 include a mixed alignment layer, but at least one of the two panels 100 and 200 may include a mixed alignment layer. Although the lower panel 100 and the upper panel 200 both include the alignment agent 20 in the illustrated embodiment, at least one of the two panels 100 and 200 may include the alignment agent 20 have.

Although not shown, the first substrate 110 or the second substrate 210 is connected to a switching element, for example, a thin film transistor (TFT), and a switching element, which are connected to signal lines such as a gate line and a data line, A color filter, a light shielding member, a common electrode, and the like may be formed.

Next, display characteristics of a liquid crystal display device according to an experimental example of the present invention will be described with reference to FIGS. 11A, 11B, and 11C. FIG. 11A, 11B and 11C are graphs showing the results of domain stability evaluation of a liquid crystal display according to an experimental example of the present invention. 11A to 11C, a solid line shown in each figure represents a domain boundary. FIG. 11A shows a case where a liquid crystal layer having a negative dielectric anisotropy is oriented by using a conventional vertical alignment film, FIG. The thickness of the vertical alignment film is about 5 nm, and FIG. 11C shows a case where the alignment film includes the alignment film including the horizontal alignment film and the vertical alignment film, The thickness of the alignment layer is about 30 nm or more.

Referring to FIG. 11A, when the liquid crystal layer having a negative dielectric anisotropy is oriented by using the vertical alignment film, it is found that the boundaries of the four domains are unclear. That is, it is difficult to realize a twisted nematic mode having four stable domains.

Referring to FIG. 11B, when a liquid crystal layer having negative dielectric anisotropy is oriented by using an alignment film including a horizontal alignment film and a vertical alignment film, the boundaries of the four domains are clear, and a twisted nematic Mode can be implemented.

11C, even if a liquid crystal layer having a negative dielectric anisotropy is oriented by using an alignment film including a horizontal alignment film and a vertical alignment film, the thickness of the vertical alignment film may be different from the thickness of the vertical alignment film according to the liquid crystal display according to the embodiment of the present invention It is difficult to realize a twisted nematic mode having four stable domains because the influence of the horizontal anchoring energy caused by the horizontal alignment film becomes small when the thickness is larger than about 30 nm. Therefore, like the liquid crystal display according to the embodiment of the present invention, the liquid crystal layer having the negative dielectric anisotropy is aligned by using the alignment film including the horizontal alignment film and the vertical alignment film, and the thickness of the vertical alignment film is formed to be about 30 nm or less The combination of the horizontal alignment film material and the anchoring energy of the vertical alignment material can maintain a twisted nematic mode due to the horizontal alignment material while having a large polar angle by the vertical alignment material, It is possible to realize an inverted twisted nematic liquid crystal display device.

12 is a graph illustrating the results of implementation of a multi-domain liquid crystal display device according to an alignment film condition of a liquid crystal display device according to one experimental example of the present invention.

12, the curve shows the twist deformation energy of the liquid crystal according to each condition, and each dot (a, b, c, d, e) shows actual experimental results. As a result of the experiment, the dot (a, b) can not implement the multi-domain inverse TN mode, and the liquid crystal is oriented in a similar manner to the ECB mode. In the case of the dot (c, d, e) I could. Experimental results show that if the azimuthal anchoring energy is larger than the value indicated by the solid line (x), a multi-domain inverse TN mode can be realized. Therefore, like the liquid crystal display device according to the embodiment of the present invention, it is possible to realize a multi-domain reverse-TN mode in a stable orientation when an orientation film including a horizontal orientation film and a vertical orientation film is included and the thickness of the vertical orientation film is about 30 nm or more .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

Claims (8)

A first substrate;
A first horizontal alignment layer disposed on the first substrate and providing a first anchoring energy;
A first vertical alignment layer disposed over the first horizontal alignment layer and providing a second anchoring energy;
A second substrate facing the first substrate;
A second horizontal alignment film disposed on the second substrate;
A second vertical alignment film disposed on the second horizontal alignment film, and
And a liquid crystal layer injected between the first substrate and the second substrate and made of liquid crystal molecules,
Wherein the first vertical alignment layer further comprises an alignment control material,
Wherein the alignment control material applies a voltage in a state in which the liquid crystal layer is injected between the first substrate and the second substrate to adjust a linear gradient of the liquid crystal molecules of the liquid crystal layer to a first anchoring energy And a second anchoring energy generated by the first vertical alignment film, and then polymerized by irradiation with ultraviolet light.
The method according to claim 1,
Wherein the liquid crystal molecules of the liquid crystal layer have a positive dielectric anisotropy.
The method according to claim 1,
Wherein the liquid crystal molecules of the liquid crystal layer have a negative dielectric anisotropy.
The method according to claim 1,
Wherein the liquid crystal layer comprises four domains in which alignment directions of liquid crystal molecules are different through adhesion between the first substrate and the second substrate.
A liquid crystal display comprising a first substrate, a first horizontal alignment film disposed on the first substrate and providing a first anchoring energy, and a second vertical alignment film disposed on the first horizontal alignment film and providing a second anchoring energy, A first step of preparing a first step;
A second step of preparing a second substrate;
A third step of injecting a liquid crystal layer made of liquid crystal molecules between the first substrate and the second substrate;
Applying a voltage in a state in which the liquid crystal layer is injected between the first substrate and the second substrate so that a line inclination of the liquid crystal molecules of the liquid crystal layer is different from a first anchoring energy by the first horizontal alignment film, A fourth step of pre-aligning with a pre-alignment by a combination of second anchoring energies by the vertical alignment film; And
And after the fourth step, ultraviolet light is irradiated to polymerize the alignment control material with the linearly oriented linearizer.
6. The method of claim 5,
Wherein the liquid crystal molecules of the liquid crystal layer have positive dielectric anisotropy.
6. The method of claim 5,
Wherein the liquid crystal molecules of the liquid crystal layer have negative dielectric anisotropy.
6. The method of claim 5,
Wherein the liquid crystal layer includes four domains in which alignment directions of liquid crystal molecules are different through adhesion between the first substrate and the second substrate.

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