KR101667052B1 - Liquid crystal display - Google Patents

Abstract

According to an embodiment of the present invention, by orienting a ferroelectric liquid crystal using an orientation film including a horizontal orientation film and a vertical orientation film on a substrate, the rotation axis of the motion locus of the ferroelectric liquid crystal molecules is 90 degrees +/- 12 degrees with respect to the surface of the substrate. Can be arranged. Thus, it is possible to provide a uniform alignment over the entire surface of the substrate, thereby providing a liquid crystal display device capable of continuous gradation display with a high contrast ratio and a fast response speed.

Description

[0001] LIQUID CRYSTAL DISPLAY [0002]

The present invention relates to a liquid crystal display device.

When a ferroelectric liquid crystal is used in a liquid crystal display device, a high response speed is very short as compared with liquid crystal display devices of other modes, and high-speed driving is possible. However, there is a problem that it is difficult to obtain a uniform orientation on the entire surface of the substrate and the image quality is deteriorated.

Particularly, in the ferroelectric liquid crystal display device, since the rotation axes of the ferroelectric liquid crystal are arranged asymmetrically about the axis perpendicular to the substrate surface, the change in the contrast ratio due to the change of the azimuth angle in the direction inclined about the axis perpendicular to the substrate surface Asymmetrically. Therefore, the image quality is degraded and uniform gradation display is impossible.

SUMMARY OF THE INVENTION The present invention provides a ferroelectric liquid crystal display capable of uniform gradation display, having an excellent viewing angle, and having a fast response speed.

According to an embodiment of the present invention, a ferroelectric liquid crystal is oriented by using an alignment layer in which a horizontal alignment film and a vertical alignment film are laminated on a substrate, thereby aligning the liquid crystal so that the rotation axis of the motion locus of the ferroelectric liquid crystal molecules is perpendicular to the surface of the substrate .

According to another embodiment of the present invention, a ferroelectric liquid crystal can be aligned by using an alignment film in which a horizontal alignment film and a vertical alignment film are mixed on a substrate. Thereby, the liquid crystal can be arranged such that the rotation axis of the ferroelectric liquid crystal molecules is perpendicular to the surface of the substrate.

Accordingly, it is possible to provide a uniform and stable alignment over the entire surface of the substrate, thereby providing a liquid crystal display device capable of continuous gradation display with a high contrast ratio and having a fast response speed.

According to an embodiment of the present invention, a liquid crystal can be arranged such that the rotation axis of the ferroelectric liquid crystal molecules is perpendicular to the surface of the substrate by orienting the ferroelectric liquid crystal using an alignment film including a horizontal alignment film and a vertical alignment film on the substrate. Thus, it is possible to provide a uniform alignment over the entire surface of the substrate, thereby providing a liquid crystal display device capable of continuous gradation display with a high contrast ratio and a fast response speed.

1 is a cross-sectional view illustrating a liquid crystal display device according to an embodiment of the present invention.
2 is a cross-sectional view illustrating a liquid crystal display device according to another embodiment of the present invention.
3 is a cross-sectional view illustrating a liquid crystal display device according to another embodiment of the present invention.
4 is a cross-sectional view illustrating a liquid crystal display device according to another embodiment of the present invention.
FIGS. 5 to 8 are graphs showing the results of the pre-alignment of the alignment film of the liquid crystal display device according to the 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 be apparent from and elucidated with reference to the embodiments described hereinafter in conjunction with 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 liquid crystal display according to an embodiment of the present invention will be described with reference to FIG. 1 is a cross-sectional view illustrating a liquid crystal display device according to an embodiment of the present invention.

Referring to FIG. 1, 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 electrode 120 and a second electrode 130 disposed on the first insulating substrate 110 and a first horizontal alignment layer la, And a first alignment layer 11a including a first vertical alignment layer 1b disposed on the first alignment layer 1a. The first horizontal alignment layer 1a and the first vertical alignment layer 1b may include at least one of PI, a photo alignment layer, nylon, PVC, and PVA.

The first electrode 120 and the second electrode 130 may have different potentials and may be formed of a transparent conductor.

The upper display panel 200 is disposed on the second insulating substrate 210 and includes a second horizontal alignment film 2a and a second vertical alignment film 2b disposed on the second horizontal alignment film 2a. 21a. The second horizontal alignment film 2a and the second vertical alignment film 2b may include at least one of PI, a photo alignment layer, nylon, PVC, and PVA.

The first alignment layer 11a of the lower panel 100 and the second alignment layer 21a of the upper panel 200 may be rubbed in different directions.

The first horizontal alignment film 1a may be laminated on the first substrate 110 of the lower panel 100 without rubbing and the first vertical alignment film 1b may be laminated thereon, The first vertical alignment film 1a may be laminated on the first horizontal alignment film 1a after rubbing in a desired direction.

Similarly to the second horizontal alignment film 2a and the second vertical alignment film 2b of the upper panel 200, the second horizontal alignment film 2a is laminated on the second substrate 210, The second vertical alignment film 2b may be laminated or the second horizontal alignment film 2a may be laminated on the second substrate 210 and thereafter rubbed in a desired direction and then a second vertical alignment film 2b may be formed thereon Or may be laminated.

The vertical alignment layers 1b and 2b are formed by mixing a vertical alignment material with a solvent (NMP: BL: BC). The thickness of the vertical alignment 130 varies depending on the content of the vertical alignment film material (capacity percentage: wt%).

The first alignment film 11a and the second alignment film 21a include a photo alignment material and can be optically aligned. Specifically, the photo-alignment material can be classified into a photo-decomposing material, a photo-isomerizing material, a photo-curing material and a photopolymerizing material depending on the kind of reaction to light. In the case of photodegradation materials, the depolarization of the polymer chains can be anisotropically caused by the polarized UV, and thus the photo-alignment can be performed using the structural anisotropy generated thereby. For example, when polyimide is irradiated with polarized UV, the chain is broken and oxidation reaction is accompanied. Such materials can have high 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.

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

All of the alignment layers according to the embodiment of the present invention are rubbed so that the liquid crystal molecules disposed thereon have a predetermined pre-tilt. In this specification, the linear alignment layer may have an angle and a direction Hereinafter, it is defined as a polar angle (0-180) and an azimuthal angle (0-360), respectively. That is, the pre-warp yarns can be interpreted to include both an azimuthal angle (0 to 360) and a polar angle (-90 to + 90 degrees). 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 an angle at which the alignment adjusting agent or the liquid crystal is tilted with respect to a line perpendicular to the horizontal surface of the substrate (normal to the substrate surface).

The liquid crystal layer 3 includes a plurality of ferroelectric liquid crystal molecules 31. The ferroelectric liquid crystal molecules 31 have an angle in the range of approximately 90 degrees +/- 12 degrees, for example, approximately perpendicular to the surfaces of the substrates 110 and 210 For example, 360 degrees about an axis to be formed, and spirally twisted. In the case of the liquid crystal display according to the present embodiment, the liquid crystal molecules 31 are twisted spirally by about 360 degrees. However, the angle of rotation of the liquid crystal varies depending on the pitch of the liquid crystal layer 3 and the cell gap It is possible. One end of the liquid crystal molecule 31 is fixed at the vertex of the cone 400 and the other end is fixed at the vertex of the cone 400 ) In a certain direction on the circumference of the circle. Herein, when the cone angle of the cone 400 indicating the direction of movement of the liquid crystal molecules 31 is defined as a first angle? 1, a rotation angle of the liquid crystal molecules rotating on the basis of the plane perpendicular to the substrate The angle formed by the axis, the cone angle? 1 of the cone 400 indicating the direction of motion of the liquid crystal molecules 31, and the angle? 2 at which the liquid crystal molecules 31 are inclined with respect to the horizontal plane of the substrate, 90 degrees.

That is, the ferroelectric liquid crystal molecules 31 are oriented such that the central axis of the cone 400 indicating the motion locus forms an angle within a range of about 90 degrees +/- 12 degrees with respect to the horizontal plane of the substrates 110 and 210 . Thereby, the liquid crystal molecules can move symmetrically about an axis that forms an angle close to a vertical direction with respect to the horizontal plane of the substrate.

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, on the first substrate 110 or the second substrate 210, a switching element such as a thin film transistor (TFT) connected to a signal line such as a gate line or a data line and a signal line, a color filter, Etc. may be formed. At least one of the first electrode 120 and the second electrode 130 may be connected to the switching device.

In the case of the liquid crystal display device according to the embodiment of the present invention, since the liquid crystal is aligned by using the alignment film including the horizontal alignment film and the vertical alignment film, by combining the anchoring energies of the horizontal alignment film and the vertical alignment film, And a polar angle having an intermediate value of the polar angle of the vertical alignment film. Specifically, in the case of a horizontal alignment film, it has a polar angle of about 4-5 선, and a vertical alignment film has a polar angle of about 89-90 선. Therefore, in the case of the liquid crystal display device according to the present embodiment, the liquid crystal can be oriented so as to have a polar angle of the pre-warp yarn of a desired angle. For example, when the thickness of the vertical alignment film is increased compared to the horizontal alignment film, the polar angle of the pre-warp yarn becomes larger, and in the opposite case, the polar angle of the pre-warp yarn becomes smaller. Therefore, in the case of the 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. That is, the line tilt angle of the liquid crystal molecules can be controlled so that the conical angle of the cone in which the ferroelectric liquid crystal molecules move is equal to the polar angle of the liquid crystal molecules.

Hereinafter, a liquid crystal display device according to another embodiment of the present invention will be described with reference to FIG. 2 is a cross-sectional view of a liquid crystal display device according to another embodiment of the present invention.

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

Referring to FIG. 2, 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 interposed therebetween.

The lower panel 100 includes a first electrode 120 and a second electrode 130 disposed on the first insulating substrate 110 and a third alignment layer 130 disposed on the first electrode 120 and the second electrode 130 and having a horizontal alignment layer and a vertical alignment layer (11b). The third alignment layer 11b may include at least one of PI, a photo alignment layer, nylon, PVC, and PVA.

The first electrode 120 and the second electrode 130 may have different potentials and may be formed of a transparent conductor.

The upper display panel 200 includes a second insulating substrate 210 and a fourth alignment layer 21b disposed on the second insulating substrate 210 and including a horizontal alignment layer and a vertical alignment layer. The fourth alignment layer 21b may include at least one of PI, a photo alignment layer, nylon, PVC, PVA, and the like.

The third alignment layer 11b of the lower panel 100 and the fourth alignment layer 21b of the upper panel 200 may be rubbed in different directions.

The third alignment film 11b and the fourth alignment film 21b include a photo alignment material and can be optically aligned. Specifically, the photo-alignment material can be classified into a photo-decomposing material, a photo-isomerizing material, a photo-curing material and a photopolymerizing material depending on the kind of reaction to light. In the case of photodegradation materials, the depolarization of the polymer chains can be anisotropically caused by the polarized UV, and thus the photo-alignment can be performed using the structural anisotropy generated thereby. For example, when polyimide is irradiated with polarized UV, the chain is broken and oxidation reaction is accompanied. Such materials can have high 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.

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

Although not shown, a switching element such as a thin film transistor (TFT) or the like connected to a signal line such as a gate line, a data line, and the like and a signal line is formed between the first insulating substrate 110 and the third alignment film 11b And a color filter, a light shielding member, a common electrode, or the like may be formed between the second insulating substrate 210 and the fourth alignment film 21b.

However, unlike the liquid crystal display device according to the embodiment shown in FIG. 1, the third alignment film 11b and the fourth alignment film 21b of the liquid crystal display device according to the present embodiment are formed by mixing a horizontal alignment material and a vertical alignment material .

The third alignment film 11b and the fourth alignment film 21b can be formed by mixing a vertical alignment material with a solvent (NMP: BL: BC) and mixing the alignment film with the horizontal alignment film. The polar angle of the pre-warp yarn by the third alignment film 11b and the fourth alignment film 21b is changed according to the content of the vertical alignment film material (capacity percentage: wt%).

The liquid crystal layer 3 includes a plurality of ferroelectric liquid crystal molecules 31. The ferroelectric liquid crystal molecules 31 have an angle in the range of approximately 90 degrees +/- 12 degrees, for example, approximately perpendicular to the surfaces of the substrates 110 and 210 For example, 360 degrees about an axis to be formed, and is spirally twisted. In the case of the liquid crystal display according to the present embodiment, the liquid crystal molecules 31 are twisted spirally by about 360 degrees. However, the angle of rotation of the liquid crystal varies depending on the pitch of the liquid crystal layer 3 and the cell gap It is possible. One end of the liquid crystal molecule 31 is fixed to the vertex of the cone 400 and the other end of the liquid crystal molecule 31 is fixed on the circumference of the cone 400 And it moves in the form of rotating in a constant direction. Herein, when the cone angle of the cone 400 indicating the direction of movement of the liquid crystal molecules 31 is defined as a first angle? 1, a rotation angle of the liquid crystal molecules rotating on the basis of the plane perpendicular to the substrate The angle formed by the axis, the cone angle? 1 of the cone 400 indicating the direction of motion of the liquid crystal molecules 31, and the angle? 2 at which the liquid crystal molecules 31 are inclined with respect to the horizontal plane of the substrate, 90 degrees.

That is, the ferroelectric liquid crystal molecules 31 are oriented so that the center axis of the cone 400 indicating the direction of motion has a line inclination such that the center axis of the cone 400 has an angle within a range of about 90 degrees +/- 12 degrees with respect to the horizontal plane of the substrates 110 and 210 . Thereby, the liquid crystal molecules can move symmetrically about an axis that forms an angle close to a vertical direction with respect to the horizontal plane of the substrate.

In the case of the liquid crystal display device according to the embodiment of the present invention, since the liquid crystal is aligned by using the alignment film in which the horizontal alignment film and the vertical alignment film are mixed, the horizontal alignment film and the vertical alignment film are formed by the combination of the anchoring energies of the horizontal alignment film and the vertical alignment film. A polar angle having a middle value of the polar angle of the vertical alignment film can be realized.

3, a liquid crystal display device according to another embodiment of the present invention will be described. The liquid crystal display device according to this embodiment is similar to the liquid crystal display device according to the embodiment shown in Fig.

Referring to FIG. 3, 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 electrode 120 and a second electrode 130 disposed on the first insulating substrate 110 and a second electrode 130 disposed on the first electrode 120 and the second electrode 130. The first alignment base film 1c, And a fifth alignment layer 11c including a first alignment control layer 1d extending from the first alignment layer 1c. The fifth alignment layer 11c may include at least one of PI, a photo alignment layer, nylon, PVC, and PVA.

The first electrode 120 and the second electrode 130 may have different potentials and may be formed of a transparent conductor.

The upper display panel 200 is disposed on the second insulating substrate 210 and the second insulating substrate 210 and includes a second alignment base layer 2c and a second alignment base layer 2c extending from the second alignment base layer 2c, And a sixth alignment layer 21c including a layer 2d. The sixth alignment layer 21c may include at least one of PI, a photo alignment layer, nylon, PVC, and PVA.

The fifth alignment layer 11c of the lower panel 100 and the sixth alignment layer 21c of the upper panel 200 may be rubbed in different directions.

Although not shown, a switching element such as a thin film transistor (TFT) or the like connected to a signal line such as a gate line or a data line and a signal line is formed between the first insulating substrate 110 and the fifth alignment film 11c And a color filter, a light shielding member, a common electrode, and the like may be formed between the second insulating substrate 210 and the sixth alignment film 21c.

Unlike the liquid crystal display device according to the embodiment shown in FIG. 2, however, the alignment films 11c and 21c of the liquid crystal display device according to the present embodiment are formed with the aligned base films 1c and 2c and the aligned base films 1c and 2c, And an alignment control layer (1d, 2d) extending from the substrate.

The first alignment base film 1d and the second alignment base film 2d include a photo alignment material and can be optically aligned. Specifically, the photo-alignment material can be classified into a photo-decomposing material, a photo-isomerizing material, a photo-curing material and a photopolymerizing material depending on the kind of reaction to light. In the case of photodegradation materials, the depolarization of the polymer chains can be anisotropically caused by the polarized UV, and thus the photo-alignment can be performed using the structural anisotropy generated thereby. For example, when polyimide is irradiated with polarized UV, the chain is broken and oxidation reaction is accompanied. Such materials can have high 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.

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

The alignment control layers 1d and 2d are formed by photopolymerizing a photopolymerizable monomer or an oligomer. Examples of the photopolymerizable monomer or oligomer include Reactive Mesogen (RM) and NOA series from Norland. Reactive mesogens (RM) refer to polymerizable mesogenic compounds. A "mesogenic compound" or "mesogenic material" includes one or more rod-shaped, plate-like or disk-shaped mesogenic groups, i.e., materials or compounds containing groups with the ability to induce liquid crystalline phase behavior. Liquid crystal compounds with rod-like or plate-like groups are known in the art as calamitic liquid crystals, and liquid crystal compounds with disc-shaped groups are known in the art as discotic liquid crystals. The compound or substance containing the mesogenic group is not necessarily required to represent a liquid crystal phase as such. It is also possible to exhibit liquid crystal phase behavior only in mixtures with other compounds, or in polymerization of mesogenic compounds or substances, or mixtures thereof.

Reactive mesogens are materials that are polymerized by light, such as ultraviolet light, and are oriented according to the orientation of adjacent materials. An example of a reactive mesogen is a compound represented by the following formula:

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.

The first alignment base film (1c) and the second alignment base film (2c) are alignment films in which a horizontal alignment material and a vertical alignment material are mixed. The first alignment base film 1c and the second alignment base film 2c can be formed by mixing a vertical alignment material with a solvent (NMP: BL: BC) and mixing them in a horizontal alignment film. The polar angle of the first alignment base film 1d and the second alignment base film 2d differ depending on the content of the vertical alignment film material (capacity percentage: wt%).

However, according to the liquid crystal display device according to another embodiment of the present invention, the first alignment base film 1c and the second alignment base film 2c may include a horizontal alignment material and a vertical alignment material, The vertical alignment material layer may have a laminated structure.

The alignment control layers 1d and 2d are photopolymerized in accordance with the initial alignment state of the liquid crystal molecules 31 to enhance the linear inclination of the liquid crystal molecules 31 to stabilize the alignment state.

The liquid crystal layer 3 includes a plurality of ferroelectric liquid crystal molecules 31. The ferroelectric liquid crystal molecules 31 have an angle in the range of approximately 90 degrees +/- 12 degrees, for example, approximately perpendicular to the surfaces of the substrates 110 and 210 For example, 360 degrees about an axis to be formed, and spirally twisted. In the case of the liquid crystal display according to the present embodiment, the liquid crystal molecules 31 are twisted spirally by about 360 degrees. However, the angle of rotation of the liquid crystal varies depending on the pitch of the liquid crystal layer 3 and the cell gap It is possible. One end of the liquid crystal molecule 31 is fixed to the vertex of the cone 400 and the other end of the liquid crystal molecule 31 is fixed on the circumference of the cone 400 And it moves in the form of rotating in a constant direction. Herein, when the cone angle of the cone 400 indicating the direction of movement of the liquid crystal molecules 31 is defined as a first angle? 1, a rotation angle of the liquid crystal molecules rotating on the basis of the plane perpendicular to the substrate The sum of the angle formed by the axis of the liquid crystal molecules 31 and the cone angle? 1 of the cone 400 indicating the direction of motion of the liquid crystal molecules 31 and the inclination angle? 2 of the liquid crystal molecules 31 with respect to the horizontal plane of the substrate is about 90 degrees.

That is, the ferroelectric liquid crystal molecules 31 are oriented so that the center axis of the cone 400 indicating the direction of motion has a line inclination such that the center axis of the cone 400 has an angle within a range of about 90 degrees +/- 12 degrees with respect to the horizontal plane of the substrates 110 and 210 . Thereby, the liquid crystal molecules can move symmetrically about an axis that forms an angle close to a vertical direction with respect to the horizontal plane of the substrate.

In the case of the liquid crystal display device according to the embodiment of the present invention, since the liquid crystal is aligned by using the alignment film in which the horizontal alignment film and the vertical alignment film are mixed, the horizontal alignment film and the vertical alignment film are formed by the combination of the anchoring energies of the horizontal alignment film and the vertical alignment film. A polar angle having a middle value of the polar angle of the vertical alignment film can be realized.

In the illustrated embodiment, the alignment bases 1c and 2c use an alignment material in which a horizontal alignment film and a vertical alignment film are mixed. However, like the liquid crystal display device according to the embodiment shown in FIG. 1, the horizontal alignment layer and the vertical alignment layer And may have a laminated structure.

The operation of the liquid crystal display according to the embodiment of the present invention will now be described with reference to FIG. 4 is a cross-sectional view illustrating an operation of a liquid crystal display device according to an embodiment of the present invention.

4, the liquid crystal molecules 31 of the liquid crystal display device are oriented such that the axis of the cone forming the locus of motion of the liquid crystal molecules 31 is perpendicular to the surfaces of the substrates 110 and 210 by the orientation films 11 and 21. When different voltages are applied to the two electrodes 120 and 130 of the liquid crystal display device, an electric field is generated between the two electrodes 120 and 130. When the electric field is generated, the liquid crystal molecules 31 are rotated along the conical motion plane according to the polarity of the electric field due to the polarity interaction between the polarization moment of the liquid crystal molecules 31 and the electric field. 4A, all the liquid crystal molecules 31 move backward due to the electric field and the polarization moment of the liquid crystal molecules 31, and all the liquid crystal molecules 31 move forward in FIG. 4B .

As described above, the liquid crystal molecules 31 of the liquid crystal display according to the present embodiment are symmetrically moved about an axis substantially perpendicular to the surfaces of the substrates 110 and 210. Therefore, deterioration in image quality due to asymmetric movement of the liquid crystal molecules 31 can be prevented, and by making the direction of movement of the liquid crystal molecules 31 within one pixel, gradation display is possible and the response speed can be increased .

5 to 8, a description will be given of the line inclination result of the alignment film of the liquid crystal display device according to the experimental example of the present invention. FIGS. 5 to 8 are graphs showing the results of the pre-alignment of the alignment film of the liquid crystal display device according to the experimental example of the present invention.

Referring to FIG. 5, it can be seen that, in the case of an alignment film in which a vertical alignment film is laminated on a horizontal alignment film like the liquid crystal display device according to the embodiment shown in FIG. 1, the polar angle of the linear alignment film can be adjusted according to the thickness of the vertical alignment film . Specifically, when the vertical alignment film is thick, the pretilt angle (90 degrees-polar angle) becomes large. When the vertical orientation film becomes thin, the pretilt angle (90 degrees-polar angle) becomes small. As a result, the liquid crystal molecules 31 can be oriented so as to have a linear gradient angle nearly equal to the conical angle of the cone forming the locus of movement of the ferroelectric liquid crystal molecules 31, So that it is possible to move symmetrically about the axis constituting the axis.

Referring to FIG. 6, it can be seen that, in the case of an alignment film in which a horizontal alignment film and a vertical alignment film are mixed, as in the liquid crystal display device according to the embodiment shown in FIG. 2, the polar angle of the linear alignment film can be adjusted according to the content of the vertical alignment material there was. Specifically, as the content of the vertical alignment material increases, the pretilt angle (90 degrees-polar angle) increases, and as the content of the vertical orientation material decreases, the pretilt angle (90 degrees-polar angle) becomes smaller. As a result, the liquid crystal molecules 31 can be oriented so as to have a linear gradient angle nearly equal to the conical angle of the cone forming the locus of movement of the ferroelectric liquid crystal molecules 31, So that it is possible to move symmetrically about the axis constituting the axis.

Referring to FIG. 7, in the case of aligning the alignment film laminated on the horizontal alignment film like the liquid crystal display device according to the embodiment shown in FIG. 1, by adjusting the irradiation time of ultraviolet rays or the thickness of the vertical alignment film, Can be controlled. Specifically, when the irradiation time of ultraviolet rays is increased or the thickness of the vertical alignment film is made thinner, the pretilt angle (90 degrees-polar angle) becomes smaller and the irradiation time of ultraviolet rays decreases, 90 degrees - polar angle) was found to be larger.

Referring to FIG. 8, when the orientation film in which the horizontal alignment film and the vertical alignment film are mixed is light-converged as in the liquid crystal display device according to the embodiment shown in FIG. 2, by adjusting the irradiation time of ultraviolet rays or the thickness of the vertical alignment film, Can be controlled. Specifically, when the irradiation time of ultraviolet rays is increased or the content of the vertical alignment material is decreased, the pretilt angle (90 degrees-polar angle) becomes smaller, and when the irradiation time of ultraviolet rays decreases or the content of the vertically oriented substance increases, The square (90 degrees - polar angle) was found to be larger.

As described above, the liquid crystal display according to the embodiment of the present invention aligns the ferroelectric liquid crystal using an orientation film including a horizontal alignment film and a vertical alignment film on the substrate so that the rotation axis of the motion locus of the ferroelectric liquid crystal molecules is perpendicular to the surface of the substrate Liquid crystal can be arranged. Thus, it is possible to provide a uniform alignment over the entire surface of the substrate, thereby providing a liquid crystal display device capable of continuous gradation display with a high contrast ratio and a fast response speed.

In the above-described embodiments, the structure in which the first electrode and the second electrode are formed on the same substrate has been described. However, the first electrode and the second electrode may be formed on different substrates or may be formed on different layers , And may have a linear or plate-like planar shape.

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 (17)

The first substrate,
A first electrode and a second electrode disposed on the first substrate,
A first alignment layer disposed on the first electrode and the second electrode, the first alignment layer including a horizontal alignment material and a vertical alignment material,
A second substrate facing the first substrate,
A second alignment film disposed on the second substrate and including a horizontal alignment material and a vertical alignment material,
And a liquid crystal layer disposed between the first substrate and the second substrate and including ferroelectric liquid crystal molecules,
(90 degrees-polar angle) of the liquid crystal molecules, and a plane in which the rotational axis of the rotational motion of the liquid crystal molecules is perpendicular to the surface of the first substrate And the sum of the angles is 90 degrees.
The method of claim 1,
Wherein the first alignment layer includes a first horizontal alignment layer and a first vertical alignment layer which are stacked.
3. The method of claim 2,
Wherein the second alignment layer comprises a second horizontal alignment layer and a second vertical alignment layer which are stacked.
4. The method of claim 3,
Wherein the liquid crystal molecules are twisted about an axis at an angle of 90 degrees +/- 12 degrees with respect to a surface of the first substrate.
5. The method of claim 4,
Wherein the liquid crystal molecules are twisted about an axis perpendicular to the surface of the first substrate.
delete 5. The method of claim 4,
Wherein the sum of the cone angle of the cone indicating the direction of motion of the liquid crystal molecules and the line inclination angle (90 degrees-polar angle) of the liquid crystal molecules is 90 degrees.
The method of claim 1,
Wherein the first alignment layer comprises a first alignment base layer and a first alignment control layer extending from the first alignment base layer.
9. The method of claim 8,
Wherein the second alignment film comprises a second alignment base film and a second alignment control layer extending from the second alignment base film.
9. The method of claim 8,
Wherein the liquid crystal molecules are twisted about an axis at an angle of 90 degrees +/- 12 degrees with respect to a surface of the first substrate.
11. The method of claim 10,
Wherein the liquid crystal molecules are twisted about an axis perpendicular to the surface of the first substrate.
11. The method of claim 10,
(90 degrees-polar angle) of the liquid crystal molecules, and a plane in which the rotational axis of the rotational motion of the liquid crystal molecules is perpendicular to the surface of the first substrate And the sum of the angles is 90 degrees.
The method of claim 12,
Wherein the sum of the cone angle of the cone indicating the direction of motion of the liquid crystal molecules and the line inclination angle (90 degrees-polar angle) of the liquid crystal molecules is 90 degrees.
The method of claim 1,
Wherein the liquid crystal molecules are twisted about an axis at an angle of 90 degrees +/- 12 degrees with respect to a surface of the first substrate.
The method of claim 14,
Wherein the liquid crystal molecules are twisted about an axis perpendicular to the surface of the first substrate.
The method of claim 14,
(90 degrees-polar angle) of the liquid crystal molecules, and a plane in which the rotational axis of the rotational motion of the liquid crystal molecules is perpendicular to the surface of the first substrate And the sum of the angles is 90 degrees.
17. The method of claim 16,
Wherein the sum of the cone angle of the cone indicating the direction of motion of the liquid crystal molecules and the line inclination angle (90 degrees-polar angle) of the liquid crystal molecules is 90 degrees.

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