Curved display device

This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. § 119 from two applications earlier filed in the Korean Intellectual Property Office of Nov. 5, 2014 and there duly assigned Serial No. 10-2014-0152780, and of Apr. 9, 2015 and there duly assigned Serial No. 10-2015-0050148.

The present disclosure relates to a curved display device. More particularly, the present disclosure relates to a curved display device having a curved display area.

A display device, e.g., a liquid crystal display, is widely applied to various information-processing devices, such as a television set, a monitor, a notebook computer, etc., to display an image. In recent years, a curved display device having a curved display area has been developed. The curved display device provides the image having improved three-dimensional effect, sense of immersion (or immersiveness), and presence to a viewer.

The present disclosure provides a curved display device having improved display quality.

Embodiments of the inventive concept provide a curved display device including a display substrate, an opposite substrate, and a liquid crystal layer interposed between the display substrate and the opposite substrate. The display substrate is curved along a first direction and includes a pixel electrode disposed in a pixel area and a second alignment layer disposed on the pixel electrode. The opposite substrate is coupled to the display substrate, curved along the first direction, and includes a common electrode generating an electric field in cooperation with the pixel electrode and a first alignment layer disposed on the common electrode. The first alignment layer comprises different material from the second alignment layer, and the first and second alignment layers align a portion of the liquid crystal molecules at pre-tilt angles. The pixel electrode includes branch portions extending in a direction inclined with respect to the first direction when viewed in a plan view, and a pitch, which is defined by a sum of a width of each branch portion and a distance between the branch portions, is within a range from about 7.5 micrometers to about 8.5 micrometers.

In the exemplary embodiment, first liquid crystal molecules, which are adjacent to the first alignment layer, of the liquid crystal molecules have a first pre-tilt (pretilt) angle. Second liquid crystal molecules, which are adjacent to the second alignment layer, of the liquid crystal molecules have a second pre-tilt angle different from the first pre-tilt angle.

Embodiments of the inventive concept provide a curved display device including a display substrate, an opposite substrate, and a liquid crystal layer interposed between the display substrate and the opposite substrate. The display substrate is curved along a first direction and includes a pixel electrode disposed in a pixel area and a second alignment layer disposed on the pixel electrode. The opposite substrate is coupled to the display substrate, curved along the first direction, and includes a common electrode generating an electric field in cooperation with the pixel electrode and a first alignment layer disposed on the common electrode. The liquid crystal layer has a thickness within a range from about 2.2 micrometers to about 2.8 micrometers. The first alignment layer comprises different material from the second alignment layer, and the first and second alignment layers align a portion of the liquid crystal molecules at pre-tilt angles.

Embodiments of the inventive concept provide a curved display device including a display substrate, an opposite substrate, and a liquid crystal layer interposed between the display substrate and the opposite substrate. The display substrate is curved along a first direction and includes a pixel electrode disposed in a pixel area and a second alignment layer disposed on the pixel electrode. The opposite substrate is coupled to the display substrate, curved along the first direction, and includes a common electrode generating an electric field in cooperation with the pixel electrode and a first alignment layer disposed on the common electrode. The liquid crystal molecules have a bend elastic constant (K 33 ) within a range from about 10.0 pN (piconewton) to about 13.0 pN (piconewton). The first alignment layer comprises different material from the second alignment layer, and the first and second alignment layers align a portion of the liquid crystal molecules at pre-tilt angles.

Embodiments of the inventive concept provide a curved display device including a display substrate, an opposite substrate, and a liquid crystal layer interposed between the display substrate and the opposite substrate. The display substrate is curved along a first direction and includes a pixel electrode disposed in a pixel area and a second alignment layer disposed on the pixel electrode. The opposite substrate is coupled to the display substrate, curved along the first direction, and includes a common electrode generating an electric field in cooperation with the pixel electrode and a first alignment layer disposed on the common electrode. The liquid crystal molecules have a negative dielectric anisotropy from about −3.2 to about −3.5. The first alignment layer comprises different material from the second alignment layer, and the first and second alignment layers align a portion of the liquid crystal molecules at pre-tilt angles.

According to the above, the brightness decrease rate, which is caused when the display panel is curved, may be minimized by controlling at least one of the pitch of the branch portions of the pixel electrode, the thickness of the liquid crystal layer, the bend elastic constant of the liquid crystal molecules, and the dielectric anisotropy of the liquid crystal molecules. Therefore, the brightness of the pixels may be prevented from being drastically deteriorated when the display panel is curved in the display panel including the domains arranged in the matrix form, and thus the display quality of the curved display device may be improved.

A more complete appreciation of the present invention, and many of the attendant advantages thereof, will become readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:

FIG. 1 is a perspective view showing a curved display device according to an exemplary embodiment of the present disclosure;

FIG. 2A is a cross-sectional view showing a display panel shown in FIG. 1 ;

FIG. 2B is a schematic cross-sectional view of the curved display device according to an embodiment of the inventive concept;

FIG. 3 is a plan view showing a pixel in the display panel of the curved display device shown in FIG. 2A ;

FIG. 4A is a view showing domains defined in the pixel shown in FIG. 3 ;

FIG. 4B is a cross-sectional view taken along a line I-I′ of FIG. 3 ;

FIG. 4C is a cross-sectional view taken along a line II-II′ of FIG. 3 ;

FIG. 4D is an enlarged view of a first pre-tilt liquid crystal illustrated in FIG. 4B ;

FIG. 4E is a view of a second pre-tilt liquid crystal illustrated in FIG. 4B ;

FIGS. 5A to 5C are photographs showing variations in brightness of first to fourth domains depending on pitches of first to fourth branch portions of a pixel electrode;

FIGS. 6A to 6C are photographs showing variations in brightness of first to fourth domains depending on a ratio of a width of the first to fourth branch portions to a distance between the first to fourth branch portions of the pixel electrode;

FIGS. 7A to 7D are photographs showing variations in brightness of first to fourth domains depending on a thickness of a liquid crystal layer shown in FIG. 4C ;

FIGS. 8A to 8C are photographs showing variations in brightness of first to fourth domains depending on a bend elastic constant of liquid crystal molecules in the liquid crystal layer shown in FIG. 4C ;

FIGS. 9A to 9F are photographs showing variations in brightness of first to fourth domains depending on a dielectric anisotropy value of the liquid crystal molecules of the liquid crystal layer shown in FIG. 4C ;

FIG. 10A is a schematic perspective view of the curved display device according to an embodiment of the inventive concept;

FIG. 10B is a schematic perspective view of a pixel and the first and second alignment layers corresponding to the pixel according to an embodiment of the inventive concept;

FIG. 10C is a schematic plan view of the first alignment layer;

FIG. 10D is a schematic plan view of the second alignment layer;

FIG. 10E is a schematic plan view of an overlapping area between the first and second alignment layers, a lower polarization plate, and an upper polarization plate;

FIG. 10F is a schematic view illustrating a state in which a user recognizes an image displayed on the curved display device according to an embodiment of the inventive concept;

FIG. 11A is a schematic perspective view of a curved display device according to a comparative example of the inventive concept;

FIG. 11B is a schematic perspective view of a pixel and first and second alignment layers corresponding to the pixel, which are included in the curved display device according to a comparative example of the inventive concept;

FIG. 11C is a schematic plan view of the first alignment layer;

FIG. 11D is a schematic plan view of the second alignment layer; and

FIG. 11E is a plan view of overlapping areas between the first and second alignment layers and polarization plates.

It will be understood that when an element or layer is referred to as being “on”, “connected to” or “coupled to” another element or layer, it can be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms, “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes” and/or “including”, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Hereinafter, the present invention will be explained in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view showing a curved display device 500 according to an exemplary embodiment of the present disclosure.

Referring to FIG. 1 , the curved display device 500 is provided with a display area DA having a curved shape. In the present exemplary embodiment, a viewpoint VP of a viewer is defined at a front of the curved display device 500 , and the display area DA has a concave-curved shape when viewed in front of the curved display device 500 .

The curved display device 500 includes a display panel 300 , and the display panel 300 is bent along a first direction D 1 to have a curved shape in the first direction D 1 . The display panel 300 has long sides E 1 and short sides E 2 . In the present exemplary embodiment, the long sides E 1 extend in a curved line shape along the first direction D 1 , and the short sides E 2 extend in a straight line shape along a second direction D 2 substantially perpendicular to the first direction D 1 .

The curved display device 500 may further include other members coupled to the display panel 300 . The members are coupled to the display panel 300 to allow the display panel 300 to be curved and to maintain the curved shape of the display panel 300 . The members include an accommodating member 580 accommodating the display panel 300 and a covering member 510 coupled to the accommodating member 580 to cover the display panel 300 .

When the display panel 300 is not coupled to the covering member 510 and the accommodating member 580 , the display panel 300 may have a flat shape. When the display panel 300 is coupled to the covering member 510 and the accommodating member 580 , the display panel 300 may have the curved shape. Thus, each of the accommodating member 580 and the covering member 510 may have the curved shape to correspond to the curved shape of the display panel 300 . For instance, a bottom portion of the accommodating member 580 , which faces a rear surface of the display panel 300 , is curved in the first direction D 1 , and a portion of the covering member 510 , which covers the long sides E 1 of the display panel 300 , is curved in the first direction D 1 .

In the present exemplary embodiment, the display panel 300 may be, but not limited to, a liquid crystal display panel. In this case, the curved display device 500 may further include a backlight assembly (not shown) accommodated in the accommodating member 580 and providing a light to the display panel 300 .

As described above, the curved display device 500 includes the display panel 300 , the backlight assembly, the accommodating member 580 , and the covering member 510 . However, the present exemplary embodiment should not be limited to the structures of the members included in the curved display device 500 , except for the display panel 300 . For instance, the backlight assembly may be an edge-illumination type backlight assembly including a light guide plate or may be a direct-illumination type backlight assembly having no light guide plate.

FIG. 2A is a cross-sectional view showing the display panel 300 of FIG. 1 . FIG. 2A shows the display panel 300 in a flat state and in a curved state. FIG. 2B is a schematic cross-sectional view of the curved display device according to an embodiment of the inventive concept. Meanwhile, even though a covering member 510 (see FIG. 1 ) and an accommodating member 580 (see FIG. 1 ) are now shown in FIG. 2 , the covering and accommodating members are coupled to the display panel 300 to allow the display panel 300 to have the curved shape.

Referring to FIG. 2A and FIG. 2B , the display panel 300 includes a display substrate 100 , an opposite substrate 200 , a liquid crystal layer LC, and a sealant ST. The display substrate 100 faces the opposite substrate 200 , and the liquid crystal layer LC is interposed between the display substrate 100 and the opposite substrate 200 . The display substrate 100 has a first curvature radius R 1 , and the opposite substrate has a second curvature R 2 radius (as shown in FIG. 2B ). The sealant ST is provided along an edge of the display substrate 100 or an edge of the opposite substrate 200 , and the display substrate 100 is coupled to the opposite substrate 200 by the sealant ST to allow the liquid crystal layer LC to be interposed between the display substrate 100 and the opposite substrate 200 .

When the display panel 300 in the flat state is curved to have a concave shape with respect to the viewpoint VP, an expansive force is generated in the display substrate 100 and a contractive force is generated in the opposite substrate 200 since a radius of curvature of the opposite substrate 200 is smaller than a radius curvature of the display substrate 100 . As a result, the opposite substrate 200 is partially lifted off, and thus a mis-alignment is caused between the display substrate 100 and the opposite substrate 200 .

Assuming that a direction to which the opposite substrate 200 is shifted with respect to the display substrate 100 is referred to as a shift direction when the mis-alignment occurs, a position of the mis-alignment and the shift direction are defined as follows.

A first area MA 1 and a second area MA 2 are defined in the display panel 300 , the first area MA 1 corresponds to a left portion of the display area DA (refer to FIG. 1 ) with respect to the viewpoint VP, and the second area MA 2 corresponds to a right portion of the display area DA with respect to the viewpoint VP. In the present exemplary embodiment, the mis-alignment may occur in each of the first and second areas MA 1 and MA 2 . When the shift direction in the first area MA 1 is referred to as a first shift direction SD 1 , the first shift direction D 1 may be roughly headed toward a left edge of the display panel 300 in the first area MA 1 . When the shift direction in the second area MA 2 is referred to as a second shift direction SD 2 , the second shift direction D 2 may be roughly headed toward a right edge of the display panel 300 in the second area MA 2 .

In general, when the mis-alignment occurs, a direction in which first pre-tilt liquid crystal molecules PL 1 (refer to FIG. 4C ) are pre-tilted by a first alignment layer AL 1 (refer to FIG. 4C ) is different from a direction in which second pre-tilt liquid crystal molecules PL 2 (refer to FIG. 4C ) are pre-tilted by a second alignment layer AL 2 (refer to FIG. 4C ) in one domain of several pixels. Accordingly, an amount of the mis-aligned liquid crystal molecules in the liquid crystal layer LC (refer to FIG. 4C ) increases, and as a result a brightness of the pixels is deteriorated. However, according to the present exemplary embodiment, the amount of the mis-aligned liquid crystal molecules in the liquid crystal layer is reduced even though the mis-alignment occurs, and thus the deterioration of the brightness in the pixel is minimized.

FIG. 3 is a plan view showing the pixel in the display panel 300 of the curved display device shown in FIG. 2A . FIG. 4A is a view showing domains defined in the pixel shown in FIG. 3 . FIG. 4B is a cross-sectional view taken along a line I-I′ of FIG. 3 . FIG. 4C is a cross-sectional view taken along a line II-II′ of FIG. 3 . FIG. 4D is an enlarged view of a first pre-tilt liquid crystal illustrated in FIG. 4B , and FIG. 4E is a view of a second pre-tilt liquid crystal illustrated in FIG. 4B .

Referring to FIGS. 3, 4A, 4B, 4C, 4D and 4E , and in particular FIG. 4B , the opposite substrate 200 includes a first base substrate S 1 , a light blocking layer BM, a common electrode CE, and the first alignment layer AL 1 . The first base substrate S 1 may be, but not limited to, a glass substrate having a light transmittance property.

The common electrode CE is disposed on the first base substrate S 1 , and the common electrode CE generates an electric field in cooperation with a pixel electrode PE to control an alignment direction of the liquid crystal molecules LM in the liquid crystal layer LC. The light blocking layer BM includes a material having a light blocking property. The light blocking layer BM is disposed on the first base substrate S 1 and overlapped with an area between a first sub-pixel area PA 1 (refer to FIGS. 3 and 4A ) and a second sub-pixel area PA 2 (refer to FIGS. 3 and 4A ).

Although the light blocking layer BM is disposed on the first base substrate S 1 in this embodiment, the present disclosure is not limited thereto. For example, in another embodiment, the light blocking layer BM may be disposed on a second base substrate S 2 .

The first alignment layer AL 1 aligns a portion of the liquid crystal molecules LM at a pre-tilt angle. The first alignment layer AL 1 aligns the first pre-tilt liquid crystal molecules PL 1 at a first pre-tilt angle a 1 . In more detail, as illustrated FIG. 4D , when a normal line NL of the first alignment layer AL 1 , a first straight line SL 1 on the first alignment layer AL 1 , and a first long axis L 11 of the first pre-tilt liquid crystal molecules PL 1 , the first pre-tilt angle a 1 may be defined as an angle between the first long axis L 11 and the first straight line SL 1 . Referring to FIGS. 3 and 4A to 4E again, for example, the first pre-tilt angle a 1 may be a value of each of the pre-tilt angles of the liquid crystal molecule adjacent to the first alignment layer AL 1 , a mean value of the pre-tilt angles of the liquid crystal molecule adjacent to the first alignment layer AL 1 , or a representative value of the pre-tilt angle of the liquid crystal molecules adjacent to the first alignment layer AL 1 .

The first pre-tilt angle a 1 is different from a second pre-tilt angle a 2 (see FIG. 4E ), and the first pre-tilt angle a 1 is greater than the second pre-tilt angle a 2 . In the exemplary embodiment, the first pre-tilt-angle a 1 may range of about 88° to about 90°, in more detail, the first pre-tilt angle a 1 may be greater than 89° and be less than 90°. Additionally, when the second pre-tilt angle a 2 is set to an angle of about 80°, 85°, 86°, or 89° according to an embodiment of the inventive concept, the first pre-tilt angle a 1 may be set to an angle of about 89.5° or about 90° that is greater than that of the second pre-tilt angle a 2 .

The liquid crystal molecules LM include the first pre-tilt liquid crystal molecules PL 1 disposed adjacent to the first alignment layer AL 1 , and the first alignment layer AL 1 reacts to reactive mesogen RM 1 to fix the first pre-tilt liquid crystal molecules PL 1 to the first alignment layer AL 1 .

The first alignment layer AL 1 is not specifically limited to a material thereof if the material is commonly used. The first alignment layer AL 1 may be formed of a monomer dimer, or oligomer of polymers such as polyimide, poly(amic acid), polyamide, poly(amic imide), polyester, polyethylene, polyurethane, or polystyrene, or mixture of the thereof. In this exemplary embodiment, the first alignment layer AL 1 may not include a photoinitiator.

Referring to FIGS. 3 and 4B , the display substrate 100 , includes a second base substrate S 2 , a gate line GL, a first data line DL 1 , a second data line DL 2 , a first thin film transistor TR 1 , a second thin film transistor TR 2 , the pixel electrode PE, a color filter CF, and a second alignment layer AL 2 .

The second base substrate S 2 may be, but not limited to, a glass substrate having a light transmittance property. The gate line GL is disposed on the second base substrate S 2 and electrically connected to the first and second thin film transistors TR 1 and TR 2 to apply a gate signal to the first and second thin film transistors TR 1 and TR 2 .

In the present exemplary embodiment, the pixel area PA is divided into the first sub-pixel area PA 1 and the second sub-pixel area PA 2 , and the pixel electrode PE includes a first sub-pixel electrode PE 1 disposed in the first sub-pixel area PA 1 and a second sub-pixel electrode PE 2 disposed in the second sub-pixel area PA 2 .

The first and second data lines DL 1 and DL 2 are insulated from the gate line GL and disposed on the second base substrate S 2 . The first data line DL 1 transfers a first data signal and the second data line DL 2 transfers a second data signal. The first thin film transistor TR 1 is electrically connected to the gate line GL, the first data line DL 1 , and the first sub-pixel electrode PE 1 . The first thin film transistor TR 1 includes a first gate electrode GE 1 , a first active pattern AP 1 ( FIG. 4B ), a first source electrode SE 1 , and a first drain electrode DEL

A gate insulating layer L 1 covers the gate electrode GE 1 and second base substrate S 2 . A second insulating layer L 2 covers the gate insulating layer L 1 and first and second thin film transistors TR 1 and TR 2 . The color filter CF is disposed on the second insulating layer L 2 to filter a light incident to the display substrate 100 through the second base substrate S 2 to a colored light.

The second alignment layer AL 2 aligns a portion of the liquid crystal molecules LM at a pre-tilt angle. In this exemplary embodiment, the second alignment layer AL 2 aligns the second liquid crystal molecules (i.e., second pre-tilt liquid crystals PL 2 ) at a second pre-tilt angle a 2 . In more detail, as shown FIG. 4E , when a normal line NL of the second alignment layer AL 2 , a second long axis L 12 on the second alignment layer AL 2 , and a second straight line SL 2 of the second pre-tilt liquid crystals PL 2 , the second pre-tilt angle a 2 may be defined as an angle between the second long axis L 12 and the second straight line SL 2 .

The first alignment layer AL 1 aligns a portion of the liquid crystal molecules LM at a pre-tilt angle. The first alignment layer AL 1 aligns the first pre-tilt liquid crystals PL 1 at a first pre-tilt angle a 1 . In more detail, as illustrated FIG. 4D , when a normal line NL of the first alignment layer AL 1 , a first long axis L 11 on the first alignment layer AL 1 , and a first long axis L 11 of the first pre-tilt liquid crystals PL 1 , the first pre-tilt angle a 1 may be defined as an angle between the first long axis L 11 and the first straight line SL 1 .

Referring to FIGS. 3 and 4A to 4E again, for example, the second pre-tilt angle a 2 may be a value of each of the pre-tilt angles of the liquid crystal molecule adjacent to the second alignment layer AL 2 , a mean value of the pre-tilt angles of the liquid crystal molecule adjacent to the second alignment layer AL 2 , or a representative value of the pre-tilt angle of the liquid crystal molecules adjacent to the second alignment layer AL 2 .

The second pre-tilt angle a 2 is different from the first pre-tilt angle a 1 . In this exemplary embodiment, the second pre-tilt angle a 2 is in a range from 80° to 90°, in more detail, the second pre-tilt angle a 2 is in a range from 80° to 89°.

The liquid crystal molecules LM comprise a second pre-tilt liquid crystals PL 2 , and the second alignment layer AL 2 react reactive mesogens RM 2 to fix the second pre-tilt liquid crystals PL 2 to the second alignment layer AL 2 .

The second alignment layer AL 2 is not specifically limited to a material thereof if the material is commonly used. For example, the second alignment layer AL 2 may include a monomer

dimer, or oligomer of polymers such as polyimide, poly(amic acid), polyamide, poly(amic imide), polyester, polyethylene, polyurethane, or polystyrene or a mixture thereof. The second alignment layer AL 2 further includes a photoinitiator. The photoinitiator may initiate a polymerization of the reactive mesogens RM 2 .

The photoinitiator is not specifically limited to a material thereof if the material is commonly used. For example, the photoinitiator may include at least one of benzyl dimethyl ketal, a-hydroxyketone, methylbenzoylformate, acrylophosphine oxide, titALocene, a-amonoketone, a-aminoacetophenone and oxime ester.

The second thin film transistor TR 2 is electrically connected to the gate line GL, the second data line DL 2 , and the second sub-pixel electrode PE 2 . The second thin film transistor TR 2 includes a second gate electrode GE 2 , a second active pattern (not shown), a second source electrode SE 2 , and a second drain electrode DE 2 .

The first and second thin film transistors TR 1 and TR 2 are turned on in response to a gate signal, a first data signal is applied to the first sub-pixel electrode PE 1 through the first thin film transistor TR 1 , and a second data signal different from the first data signal is applied to the second sub-pixel electrode PE 2 through the second thin film transistor TR 2 . The first and second sub-pixel electrodes PE 1 and PE 2 are driven by different data signals from each other, and thus different grayscale levels are displayed in the first and second sub-pixel areas PA 1 and PA 2 , respectively.

Referring again to FIG. 3 , the first sub-pixel electrode PE 1 includes a first horizontal trunk portion HS 1 , a first vertical trunk portion VS 1 , and first, second, third, and fourth branch portions B 1 , B 2 , B 3 , and B 4 .

The first horizontal trunk portion HS 1 extends in the first direction D 1 to cross the first sub-pixel area PA 1 , and the first vertical trunk portion VS 1 extends in the second direction D 2 to cross the first sub-pixel area PA 1 . The first vertical trunk portion VS 1 crosses the first horizontal trunk portion HS 1 and is connected to the first horizontal trunk portion HS 1 . In the present exemplary embodiment, the first direction D 1 crosses the second direction D 2 . More particularly, the first direction D 1 is substantially perpendicular to the second direction D 2 .

The first branch portions B 1 are branched from the first horizontal trunk portion HS 1 or the first vertical trunk portion VS 1 . The first branch portions B 1 are spaced apart from each other to allow a slit ST to be defined between two first branch portions B 1 adjacent to each other. Each of the first branch portions B 1 extends in a third direction D 3 inclined with respect to the first direction D 1 and the second direction D 2 when viewed in a plan view.

The second branch portions B 2 are branched from the first horizontal trunk portion HS 1 or the first vertical trunk portion VS 1 . Each of the second branch portions B 2 extends in a fourth direction D 4 inclined with respect to the first direction D 1 and the second direction D 2 when viewed in a plan view, and the fourth direction D 4 crosses the third direction D 3 when viewed in a plan view, however, the first and second branch portions B 1 and B 2 do not cross each other.

The third branch portions B 3 are branched from the first horizontal trunk portion HS 1 or the first vertical trunk portion VS 1 , and the fourth branch portions B 4 are branched from the first horizontal trunk portion HS 1 or the first vertical trunk portion VS 1 . Each of the third branch portions B 3 extends in the fourth direction D 4 and each of the fourth branch portions B 4 extends in the third direction D 3 when viewed in a plan view, such that the third and fourth branch portions B 3 and B 4 do not cross each other.

The second sub-pixel electrode PE 2 includes a second horizontal trunk portion HS 2 , a second vertical trunk portion VS 2 , and fifth, sixth, seventh, and eighth branch portions B 5 , B 6 , B 7 , and B 8 . In the present exemplary embodiment, the second sub-pixel electrode PE 2 may have a size greater than that of the first sub-pixel electrode PE 1 . However, since the structure of the second sub-pixel electrode PE 2 is substantially similar to that of the first sub-pixel electrode PE 1 , detailed descriptions on the second sub-pixel electrode PE 2 will be omitted.

Referring to FIG. 4A , when the first to eighth branch portions B 1 to B 8 have the above-described structure, first, second, third, and fourth domains DM 1 , DM 2 , DM 3 , and DM 4 are defined in the first sub-pixel area PA 1 , and fifth, sixth, seventh, and eighth domains DM 5 , DM 6 , DM 7 , and DM 8 are defined in the second sub-pixel area PA 2 . In the present exemplary embodiment, the first to fourth domains DM 1 to DM 4 and the fifth to eighth domains DM 5 to DM 8 are arranged in a matrix configuration, a row direction of the matrix configuration is substantially in parallel to the first direction D 1 , and a column direction of the matrix configuration is substantially in parallel to the second direction D 2 .

When the electric field is generated between the pixel electrode PE and the common electrode CE, the liquid crystal molecules in the first to eighth domains DM 1 to DM 8 are aligned by the electric field. The liquid crystal molecules in the first domain DM 1 are aligned in a first alignment direction DR 1 by the electric field, the liquid crystal molecules in the second domain DM 2 are aligned in a second alignment direction DR 2 by the electric field, the liquid crystal molecules in the third domain DM 3 are aligned in a third alignment direction DR 3 by the electric field, and the liquid crystal molecules in the fourth domain DM 4 are aligned in a fourth alignment direction DR 4 by the electric field. The first to fourth alignment directions DR 1 to DR 4 are different from each other.

The first to eighth branch portions B 1 to B 8 have the same width with each other and are arranged at regular distances. Thus, when a sum of the width of each branch portion and the distance between the branch portions is referred to as a pitch, the pitch is constant in the first to eighth branch portions B 1 to B 8 . For instance, when each of the first branch portions B 1 has a first width WT, a distance between two adjacent first branch portions of the first branch portions B 1 is a first distance DT, and the first width WT in the first to eighth branch portions B 1 to B 8 and the first distance DT in the first to eighth branch portions B 1 to B 8 are constant, the first branch portions B 1 are arranged with a first pitch PT corresponding to a sum of the first width WT and the first distance DT. The first pitch PT is constant in the first branch portions B 1 .

In the present exemplary embodiment, the first pitch PT may be within a range from about 7.5 micrometers to about 8.5 micrometers, and more particularly, the first pitch PT may be about 8.0 micrometers. Hereinafter, an effect generated when the first pitch PT has the above-described size will be described in details.

FIGS. 5A to 5C are photographs showing variations in brightness of the first to fourth domains depending on pitches of the first to fourth branch portions.

Referring to FIGS. 4C and 5A to 5C , a brightness decrease rate is changed depending on the size the pitch in the branch portions, e.g., with reference to FIG. 4C , the size of the first pitch PT of the first branch portions B 1 , and the brightness decrease rate shows a degree of decrease in the brightness in a percentage value in the first to fourth domains DM 1 to DM 4 (refer to FIG. 4A ) due to the mis-alignment described with reference to FIG. 2A , wherein the opposite substrate 200 is partially lifted off. As the brightness decrease rate increases, the degree of decrease in the brightness becomes greater by the mis-alignment, and as the brightness decrease rate decreases, the degree of decrease in the brightness becomes smaller by the mis-alignment.

As shown in FIGS. 5A to 5C , when the first pitch PT is about 4.0 micrometers (μm), the brightness decrease rate is about 10.6%, and when the first pitch PT is about 6.0 micrometers, the brightness decrease rate is about 13.3%. On the contrary, when the first pitch PT is about 8.0 micrometers, the brightness decrease rate is about 5.3%. Thus, referring to the data shown in FIGS. 5A to 5C , the brightness decrease rate is changed depending on the first pitch PT, and a size of the first pitch PT, which minimizes the brightness decrease rate, may be obtained by using the data shown in FIGS. 5A to 5C .

In the present exemplary embodiment, since the brightness decrease rate becomes minimized when the first pitch PT is about 8.0 micrometers compared to that when the first pitch PT is about 4.0 micrometers or 6.0 micrometers, the first pitch PT may be set to be about 8.0 micrometers. Although the first pitch PT is designed to have about 8.0 micrometers, the first pitch PT may be changed within a range of about ±0.5 micrometers in a manufacturing process of the first branch portions B 1 . Therefore, the first pitch PT may be set to be within a range from about 7.5 micrometers to about 8.5 micrometers.

Hereinafter, as shown in FIGS. 5A to 5C , the reason why the brightness decrease rate becomes minimized when the first pitch PT is about 8.0 micrometers is described.

An electric force generated between an edge of each first branch portion B 1 and the common electrode CE includes a vertical component and a horizontal component. The vertical component mainly causes a first alignment operation allowing the liquid crystal molecules LM of the liquid crystal layer LC to be laid on the first base substrate S 1 , and the horizontal component mainly causes a second alignment operation allowing the liquid crystal molecules LM of the liquid crystal layer LC to be rotated with respect to a rotational axis substantially perpendicular to the first base substrate S 1 . In this case, the distance between the first branch portions B 1 becomes greater when the first pitch PT is about 8.0 micrometers than when the first pitch PT is about 4.0 micrometers or 6.0 micrometers, and thus the horizontal component may increase relatively more than the vertical component.

As an amount of the horizontal component increases, the second alignment operation becomes easier. Accordingly, even though the mis-alignment occurs in the display panel 300 (refer to FIG. 2A ) and the first and second pre-tilt liquid crystals PL 1 and PL 2 are mis-aligned, the liquid crystal molecules LM have a tendency to be aligned more by the horizontal component of the electric force than by the mis-aligned first and second pre-tilt liquid crystals PL 1 and PL 2 . As a result, as in the present exemplary embodiment, when an optimal value of the first pitch PT to allow the brightness decrease rate to be minimized is obtained, the number of liquid crystal molecules mis-aligned by the first and second pre-tilt liquid crystals PL 1 and PL 2 is reduced and the brightness in the first to fourth domains is prevented from being drastically decreased.

FIGS. 6A to 6C are photographs showing variations in brightness of the first to fourth domains depending on a ratio of the width of the first to fourth branch portions to the distance between the first to fourth branch portions of the pixel electrode.

Referring to FIGS. 4C and 6A to 6C , when a value obtained by dividing the first width WT of the first branch portion B 1 by the first distance DT is defined as a width-to-distance ratio and the first pitch PT is constant, the brightness decrease rate is changed depending on the width-to-distance ratio.

More particularly, in a case that first pitch PT is constant, e.g., about 6.0 micrometers, the brightness decrease rate is about 13.3% when the width-to-distance ratio is about 1, and the brightness decrease rate is about 11.1% when the width-to-distance ratio is greater than 1. On the contrary, the brightness decrease rate is about 8.7% when the width-to-distance ratio is smaller than 1. Referring to the data shown in FIGS. 6A to 6C , the brightness decrease rate is changed depending on the width-to-distance ratio, and in the present exemplary embodiment, the width-to-distance ratio may be set to have a value smaller than 1 to minimize the brightness decrease rate.

Hereinafter, the reason why the brightness decrease rate is minimized when the width-to-distance ratio is smaller than 1 will be described. When the width-to-distance ratio is smaller than 1, the first distance DT between the first branch portions B 1 is greater than the first width WT. Accordingly, as described earlier with reference to FIGS. 5A to 5C , the amount of the horizontal component becomes greater than the amount of the vertical component of the electric force generated between each edge of the first branch portions B 1 and the common electrode CE. Therefore, the mis-alignment occurs in the display panel 300 (refer to FIG. 2A ), and the liquid crystal molecules have a tendency to be aligned more by the horizontal component of the electric force than by the first and second pre-tilt liquid crystals PL 1 and PL 2 . As a result, as in the present exemplary embodiment, when the optimal width-to-distance ratio, which minimizes the brightness decrease rate, is obtained, the number of liquid crystal molecules mis-aligned by the first and second pre-tilt liquid crystals PL 1 and PL 2 is reduced and the brightness in the first to fourth domains is prevented from being drastically decreased.

FIGS. 7A to 7D are photographs showing variations in brightness of the first to fourth domains depending on a thickness of the liquid crystal layer LC of FIG. 4C .

Referring to FIGS. 4C and 7A to 7D , the brightness decrease rate is changed depending on a thickness CG of the liquid crystal layer LC. More particularly, the brightness decrease rate is about 9.6% when the liquid crystal layer LC has the thickness CG of about 2.5 micrometers, and the brightness decrease rate is about 11.2% when the liquid crystal layer LC has the thickness CG of about 3.0 micrometers. In addition, the brightness decrease rate is about 12.7% when the liquid crystal layer LC has the thickness CG of about 3.5 micrometers, and the brightness decrease rate is about 13.3% when the liquid crystal layer LC has the thickness CG of about 4.0 micrometers. Therefore, referring to the data shown in FIGS. 7A to 7D , the brightness decrease rate is changed depending on the thickness CG of the liquid crystal layer LC, and the thickness CG of the liquid crystal layer LC, which minimizes the brightness decrease rate, may be obtained using the data.

In the present exemplary embodiment, since the brightness decrease rate is minimized when the liquid crystal layer LC has the thickness CG of about 2.5 micrometers compared to that when the liquid crystal layer LC has the thickness CG of about 3.0, 3.5, or 4.0 micrometers, the liquid crystal layer LC may be set to have the thickness CG of about 2.5 micrometers. Also, when considering tolerance in the thickness CG of the liquid crystal layer LC, the liquid crystal layer LC may have a thickness within a range from about 2.2 micrometers to about 2.8 micrometers.

In general, as the thickness CG of the liquid crystal layer LC decreases, the brightness decrease rate becomes smaller. However, when the liquid crystal layer LC has the thickness CG less than about 2.2 micrometers, the brightness in the domains where the mis-alignment does not occur may drastically decrease. Thus, the liquid crystal layer LC has the thickness CG within a range from about 2.2 micrometers to about 2.8 micrometers.

Hereinafter, the reason why the brightness decrease rate is changed depending on the thickness CG of the liquid crystal layer LC is described. As the thickness CG of the liquid crystal layer LC becomes smaller, a distance between the first branch portions B 1 and the common electrode CE decreases and the size of the electric force increases. Thus, although the mis-alignment occurs in the display panel 300 (refer to FIG. 2A ) and the first and second pre-tilt liquid crystals PL 1 and PL 2 are mis-aligned, the liquid crystal molecules LM have a tendency to be aligned more by the electric force than by the first and second pre-tilt liquid crystals PL 1 and PL 2 , which are mis-aligned. Accordingly, as in the present exemplary embodiment, when the optimal thickness CG of the liquid crystal layer LC is obtained, the number of liquid crystal molecules mis-aligned by the first and second pre-tilt liquid crystals PL 1 and PL 2 decreases in the liquid crystal layer LC and the brightness in the first to fourth domains is prevented from being drastically decreased.

FIGS. 8A to 8C are photographs showing variations in brightness of the first to fourth domains depending on a bend elastic constant of the liquid crystal molecules in the liquid crystal layer of FIG. 4C .

Referring to FIGS. 4C and 8A to 8C , the brightness decrease rate is changed depending on the bend elastic constant of the liquid crystal molecules LM of the liquid crystal layer LC. More particularly, the brightness decrease rate is about 16.2% when the liquid crystal molecules LM have the bend elastic constant of about 16.1 pN, the brightness decrease rate is about 13.3% when the liquid crystal molecules LM have the bend elastic constant of about 13.1 pN, and the brightness decrease rate is about 9.8% when the liquid crystal molecules LM have the bend elastic constant of about 10.1 pN. Thus, referring to the data shown in FIGS. 8A to 8C , the brightness decrease rate is changed depending on the bend elastic constant, and the bend elastic constant, which minimizes the brightness decrease rate, is obtained by using the data described above.

In the present exemplary embodiment, since the brightness decrease rate is more reduced when the bend elastic constant of the liquid crystal layer LC is about 10.1 pN than when the bend elastic constant of the liquid crystal layer LC is about 13.1 pN or 16.1 pN, the bend elastic constant may be set to have the optimal value of about 10.1 pN. However, when the liquid crystal layer LC has the bend elastic constant less than about 10, the brightness in the domains where the mis-alignment does not occur may drastically decrease. Thus, in the present exemplary embodiment, the liquid crystal layer LC has the bend elastic constant in a range from about 10.0 pN to about 13.0 pN.

Hereinafter, the reason why the brightness decrease rate is more reduced when the bend elastic constant of the liquid crystal layer LC is about 10.1 pN than when the bend elastic constant of the liquid crystal layer LC is about 13.1 pN or 16.1 pN is described. As the bend elastic constant of the liquid crystal layer LC becomes smaller, the liquid crystal molecules LM have a tendency to be aligned more by the electric force generated in the liquid crystal layer LC than by interaction between the liquid crystal molecules LM including the first and second pre-tilt liquid crystals PL 1 and PL 2 . Thus, although the mis-alignment occurs in the display panel 300 (refer to FIG. 2A ) and the first and second pre-tilt liquid crystals PL 1 and PL 2 are mis-aligned, the liquid crystal molecules LM have the tendency to be aligned more by the electric force than by the first and second pre-tilt liquid crystals PL 1 and PL 2 , which are mis-aligned. Accordingly, as in the present exemplary embodiment, in the case that the optimal bend elastic constant of the liquid crystal layer LC is obtained, a control capability of the electric force used to control the liquid crystal molecules LM is improved. As a result, the number of liquid crystal molecules mis-aligned by the first and second pre-tilt liquid crystals PL 1 and PL 2 decreases in the liquid crystal layer LC, and the brightness in the first to fourth domains is prevented from being drastically decreased.

FIGS. 9A to 9F are photographs showing variations of brightness in the first to fourth domains depending on a dielectric anisotropy value of the liquid crystal molecules of the liquid crystal layer of FIG. 4C .

Referring to FIGS. 4C and 9A to 9F , the brightness decrease rate is changed depending on intensity of the dielectric anisotropy Δ∈ of the liquid crystal molecules LM in the liquid crystal layer LC. More particularly, on the assumption that the bend elastic constant of the liquid crystal molecules LM is constant, the brightness decrease rate is about 10.4% when the dielectric anisotropy is about −3.5, the brightness decrease rate is about 10.8% when the dielectric anisotropy is about −3.2, and the brightness decrease rate is about 13.3% when the dielectric anisotropy is about −2.8. In addition, the brightness decrease rate is about 13.4% when the dielectric anisotropy is about −2.5, the brightness decrease rate is about 24.0% when the dielectric anisotropy is about −2.2, and the brightness decrease rate is about 25.7% when the dielectric anisotropy is about −1.9. Referring to the data shown in FIGS. 9A to 9F , the brightness decrease rate is changed depending on the intensity of dielectric anisotropy, and the dielectric anisotropy value, which minimizes the brightness decrease rate, is obtained by using the data described above.

In the present exemplary embodiment, since the brightness decrease rate is more reduced when the intensity of dielectric anisotropy is about −3.2 or −3.5 than that when the intensity of dielectric anisotropy is about −2.8, −2.5, −2.2, or −1.9, the optimal dielectric anisotropy value may be set to be within a range from about −3.2 to about −3.5.

Meanwhile, as the dielectric anisotropy value becomes greater, the liquid crystal molecules LM have a tendency to be aligned more by the electric force generated in the liquid crystal layer LC than by interaction between the liquid crystal molecules LM including the first and second pre-tilt liquid crystals PL 1 and PL 2 . Accordingly, as in the present exemplary embodiment, when the optimized dielectric anisotropy value is obtained, a control capability of the electric force on the alignment of the liquid crystal molecules LM is improved. As a result, the number of liquid crystal molecules mis-aligned by the first and second pre-tilt liquid crystals PL 1 and PL 2 decreases in the liquid crystal layer LC, and the brightness in the first to fourth domains is prevented from being drastically decreased.

FIG. 10A is a schematic perspective view of the curved display device according to an embodiment of the inventive concept. FIG. 10B is a schematic perspective view of a pixel and the first and second alignment layers corresponding to the pixel according to an embodiment of the inventive concept. FIG. 10C is a schematic plan view of the first alignment layer. FIG. 10D is a schematic plan view of the second alignment layer. FIG. 10E is a schematic plan view of an overlapping area between the first and second alignment layers, a lower polarization plate, and an upper polarization plate. FIG. 10F is a schematic view illustrating a state in which a user recognizes an image displayed on the curved display device according to an embodiment of the inventive concept.

As shown in FIG. 10A , curved display panel 300 of FIGS. 4A to 4C having the display substrate 100 , liquid crystal layer LC and opposite substrate 200 may also include a lower polarization plate POL 1 and an upper polarization plate POL 2 .

As shown in FIG. 10B a pixel PX, in alignment with first and second alignment layers AL 1 and AL 2 , includes first to fourth domains DM 1 , DM 2 , DM 3 , and DM 4 and the first and second alignment layers AL 1 and AL 2 corresponding to the pixel PX.

The second alignment layer AL 2 includes a first lower alignment area L_AA 1 , a second lower alignment area L_AA 2 , a third lower alignment area L_AA 3 , and a fourth lower alignment area L_AA 4 . The first to fourth lower alignment areas L_AA 1 , L_AA 2 , L_AA 3 , and L_AA 4 may correspond to overlap the first to fourth domains DM 1 , DM 2 , DM 3 , and DM 4 , respectively, in a sixth direction D 6 that is a normal direction of the pixel PX and a seventh direction D 7 that is opposite to the sixth direction D 6 .

The first domain DM 1 , the second domain DM 2 , the third domain DM 3 , and the fourth domain DM 4 may one-to-one correspond to the first lower alignment area L_AA 1 , the second lower alignment area L_AA 2 , the third lower alignment area L_AA 3 , and the fourth lower alignment area L_AA 4 . The second pre-tilt liquid crystal molecules PL 2 (refer to FIGS. 4B and 4C ) may be pre-tilted by the second reactive mesogens RM 2 that are polymerized with each other on each of the first to fourth lower alignment areas L_AA 1 , L_AA 2 , L_AA 3 , and L_AA 4 . As the electrical fields are formed in the liquid crystal layer LC, the second pre-tilt liquid crystals PL 2 may be more quickly aligned in a parallel direction than the liquid crystal molecules LM that are not pre-tilted. Liquid crystal molecules may be quickly rearranged from a vertically aligned state to a parallely aligned state.

First liquid crystal molecules, which are adjacent to the first alignment layer AL 1 , of the liquid crystal molecules LM are defined, and the first liquid crystal molecules are aligned to be parallel to the first pre-tilt liquid crystals PL 1 by electric fields applied to the liquid crystal layer LC. Second liquid crystal molecules, which are adjacent to the second alignment layer AL 2 , of the liquid crystal molecules LM are defined, and the second liquid crystal molecules are aligned to be parallel to the second pre-tilt liquid crystals PL 2 by the electric fields. When the electrical fields are applied to the liquid crystal layer LC, the second liquid crystal molecules and the second pre-tilt liquid crystals PL 2 may be aligned in a direction parallel to an extension direction of the first branch parts (see reference numeral B 1 of FIG. 2A ) on the first lower alignment area L_AA 1 . Here, the extension direction of the first branch parts may be substantially parallel to the first liquid crystal alignment direction DR 1 of FIG. 10C . The first liquid crystal alignment direction DR 1 may represent a mean direction of parallely aligned directions when the second liquid crystal molecules and the second pre-tilt liquid crystals PL 2 are parallely aligned on the first lower alignment area L_AA 1 .

Similarly, when the electric fields are applied to the liquid crystal layer LC, the second liquid crystal molecules and the second pre-tilt liquid crystals PL 2 are aligned in a second liquid crystal alignment direction DR 2 on the second lower alignment area L_AA 2 , the second liquid crystal molecules and the second pre-tilt liquid crystals PL 2 are aligned in a third liquid crystal alignment direction DR 3 on the third lower alignment area L_AA 3 , and the second liquid crystal molecules and the second pre-tilt liquid crystals PL 2 are aligned in a fourth liquid crystal alignment direction DR 4 on the fourth lower alignment area L_AA 4 .

The second liquid crystal alignment direction DR 2 may represent a mean direction of parallely aligned directions when the second liquid crystal molecules and the second pre-tilt liquid crystals PL 2 are parallely aligned on the second lower alignment area L_AA 2 .

The third liquid crystal alignment direction DR 3 may represent a mean direction of parallely aligned directions when the second liquid crystal molecules and the second pre-tilt liquid crystals PL 2 are parallely aligned on the third lower alignment area L_AA 3 .

The fourth liquid crystal alignment direction DR 4 may represent a mean direction of parallely aligned directions when the second liquid crystal molecules and the second pre-tilt liquid crystals PL 2 are parallely aligned on the fourth lower alignment area L_AA 4 .

Referring again to FIG. 10B , the first alignment layer AL 1 includes a first upper alignment area U_AA 1 , a second upper alignment area U_AA 2 , a third upper alignment area U_AA 3 , and a fourth upper alignment area U_AA 4 . The upper alignment areas U_AA 1 , U_AA 2 , U_AA 3 , and U_AA 4 may respectively correspond to overlap the domains DM 1 , DM 2 , DM 3 , and DM 4 in a sixth direction D 6 and seventh direction D 7 .

In this embodiment, the first alignment layer AL 1 includes the first reactive mesogens RM 1 . However, an amount of the first reactive mesogens RM 1 may be less than that of the second reactive mesogens RM 2 as described above. In another embodiment, the amount of first reactive mesogens RM 1 may be negligibly less in comparison to that of second reactive mesogens RM 2 .

Thus, the amount of first pre-tilt liquid crystals PL 1 on each of the first, second, third, and fourth upper alignment areas U_AA 1 , U_AA 2 , U_AA 3 , and U_AA 4 may be negligibly less in comparison to that of second pre-tilt liquid crystals PL 2 . Also, the amount of the first liquid crystal molecules may be negligibly less in comparison to that of second liquid crystal molecules. When a degree of an arrangement of the second liquid crystal molecules of the first lower alignment area L_AA 1 in the first liquid crystal alignment direction DR 1 is defined as a first scalar value, and a degree of an arrangement of the first liquid crystal molecules of the first upper alignment area U_AA 1 in the first liquid crystal alignment direction DR 1 is defined as a second scalar value, the second scalar value may be significantly less than the first scalar value. Additionally, since the first liquid crystal molecules are not substantially pre-tilted, a parallely aligned rate of the first liquid crystal molecules on the first upper alignment area U_AA 1 may be significantly less than that of the second liquid crystal molecules on the first lower alignment area L_AA 1 . Also, the number of first liquid crystal molecules that are aligned in parallel to the first liquid crystal alignment direction DR 1 may be significantly less than that of second liquid crystal molecules that are aligned in parallel to the first liquid crystal alignment direction DR 1 .

Similarly, when the electric fields are applied to the liquid crystal layer LC, the first liquid crystal molecules may be weakly aligned in the second liquid crystal alignment direction DR 2 on the second upper alignment area U_AA 2 , be weakly aligned in the third liquid crystal alignment direction DR 3 on the third upper alignment area U_AA 3 , and be weakly aligned in the fourth liquid crystal alignment direction DR 4 on the fourth upper alignment area U_AA 4 .

Referring to FIGS. 10A to 10E , when viewed in the fifth direction D 5 , the first and second alignment layers AL 1 and AL 2 have (refer to FIG. 10E ) first to sixth overlapping areas OVA 1 , OVA 2 , OVA 3 , OVA 4 , OVA 5 , and OVA 6 which overlap each other.

When the electric fields are applied to the liquid crystal layer LC, an optical axis direction of the liquid crystal layer LC may be equal to a mean value of the parallely aligned direction of the second liquid crystal molecules on the lower alignment areas L_AA 1 , L_AA 2 , L_AA 3 , and L_AA 4 and the parallely aligned direction of the first liquid crystal molecules on the upper alignment areas U_AA 1 , U_AA 2 , U_AA 3 , and U_AA 4 .

The second overlapping area OVA 2 may be an area on which the second lower alignment area L_AA 2 and the first upper alignment area U_AA 1 overlap each other. Since the first liquid crystal molecules are not substantially pre-tilted, and the second liquid crystal molecules are more pre-tilted, a parallely aligned rate of the first liquid crystal molecules on the first overlapping area OVA 1 may be significantly less than that of the second liquid crystal molecules. Also, the number of first liquid crystal molecules that are aligned in parallel to the second liquid crystal alignment direction DR 2 may be significantly less than that of second liquid crystal molecules that are aligned in parallel to the first liquid crystal alignment direction DR 1 .

Thus, when the electric fields are applied to the liquid crystal layer LC, the optical axis direction of the liquid crystal layer LC on the second overlapping area OVA 2 may be substantially parallel to the second liquid crystal alignment direction DR 2 . Similarly, when the electric fields are applied to the liquid crystal layer LC, an optical axis direction of the liquid crystal layer LC on the fifth overlapping area OVA 5 may be substantially parallel to the fourth liquid crystal alignment direction DR 4 .

The parallely aligned direction of the second liquid crystal molecules on the first overlapping area OVA 1 may be the substantially same as that of the first liquid crystal molecules. Thus, the optical axis direction of the liquid crystal layer LC on the first overlapping area OVA 1 is substantially parallel to the first liquid crystal alignment direction DR 1 . Similarly, an optical axis direction of the liquid crystal layer LC on the third overlapping area OVA 3 is substantially parallel to the second liquid crystal alignment direction DR 2 , an optical axis direction of the liquid crystal layer LC on the fourth overlapping area OVA 4 is substantially parallel to the third liquid crystal alignment direction DR 3 , and an optical axis direction of the liquid crystal layer LC on the sixth overlapping area OVA 6 is substantially parallel to the fourth liquid crystal alignment direction DR 4 .

The lower polarization plate POL 1 has a first transmission axis PA 1 , and the upper polarization plate POL 2 has a second transmission axis PA 2 . The first transmission axis PA 1 and the second transmission axis PA 2 are substantially perpendicular to each other. For example, when the first transmission axis PA 1 is parallel to the ninth direction D 9 , the second transmission axis PA 2 is parallel to the eighth direction D 8 . For convenience of description, FIG. 10E illustrates the lower and upper polarization plates POL 1 and POL 2 each of which has a size relatively less than that of each of the first and second alignment layers AL 1 and AL 2 .

Referring to FIGS. 10A to 10F , the optical axis direction of the liquid crystal layer LC is not parallel to the directions of the first transmission axis PA 1 of the lower polarization plate POL 1 and the second transmission axis PA 2 of the upper polarization plate POL 2 within each of the first to sixth overlapping areas OVA 1 , OVA 2 OVA 3 , OVA 4 , OVA 5 , and OVA 6 of the curved display device 500 according to an embodiment of the inventive concept. Thus, the user USER may see light passing through the first to sixth overlapping areas OVA 1 , OVA 2 OVA 3 , OVA 4 , OVA 5 , and OVA 6 .

FIG. 11A is a schematic perspective view of a curved display panel according to a comparative example of the inventive concept. FIG. 11B is a schematic perspective view of a pixel and first and second alignment layers corresponding to the pixel, which are included in the curved display device according to a comparative example of the inventive concept. FIG. 11C is a schematic plan view of the first alignment layer. FIG. 11D is a schematic plan view of the second alignment layer. FIG. 11E is a schematic plan view of overlapping areas between the first and second alignment layers and polarization plates.

As shown in FIG. 11A , curved display panel 1000 is similar to the display panel of FIGS. 2B, 4C and 10A in that it may include a second base substrate s 2 , a second alignment layer all, a liquid crystal layer 1 c , a first alignment layer all, a first base substrate s 1 , a lower polarization plate poll and an upper polarization plate pol 2 .

Referring to FIGS. 11A to 11E , a curved display panel 1000 according to a comparative example includes a first alignment layer al 1 including reactive mesogens that are polymerized with each other and a second alignment layer al 2 including reactive mesogens that are polymerized with each other. The first and second alignment layers al 1 and al 2 may include the reactive mesogens having the substantially same amount. Thus, first liquid crystal molecules of a liquid crystal layer 1 c are pre-tilted by the first alignment layer al 1 , and second liquid crystal molecules of the liquid crystal layer 1 c are pre-tilted by the second alignment layer al 2 .

Also, a pre-tilt angle of the first liquid crystal molecules may be the same as a pre-tilt angle of the second liquid crystal molecules. When electric fields are applied to the liquid crystal layer 1 c , the second liquid crystal molecules on lower alignment areas 1 _aa 1 , l_aa 2 , l_aa 3 , and l_aa 4 (see FIG. 11B ) provided on the second alignment layer al 2 and the first liquid crystal molecules on upper alignment areas u_aa 1 , u_aa 2 , u_aa 3 , and u_aa 4 provided on the first alignment layer al 1 are parallely aligned in the same direction. Since all of the first and second liquid crystal molecules are pre-tilted, rates at which the first and second liquid crystal molecules are parallely aligned may be similar to each other.

In detail, referring to FIGS. 11C and 11D , when a driving voltage is applied to apply the electric fields, the second liquid crystal molecules on the first lower alignment area l_aa 1 and the first liquid crystal molecules on the first upper alignment area u_aa 1 are parallely aligned in a first liquid crystal alignment direction DR 1 , and the second liquid crystal molecules on the second lower alignment area l_aa 2 and the first liquid crystal molecules on the second upper alignment area u_aa 2 are parallely aligned in a second liquid crystal alignment direction DR 2 . The second liquid crystal molecules on the third lower alignment area l_aa 3 and the first liquid crystal molecules on the third upper alignment area u_aa 3 are parallely aligned in a third liquid crystal alignment direction DR 3 , and the second liquid crystal molecules on the fourth lower alignment area l_aa 4 and the first liquid crystal molecules on the fourth upper alignment area u_aa 4 are parallely aligned in a fourth liquid crystal alignment direction DR 4 .

Referring to FIG. 11E , when viewed in a fifth direction D 5 (see FIG. 11B ), the first and second alignment layers al 1 and al 2 have overlapping areas which overlap each other. The overlapping areas include a first overlapping area ova 1 , a second overlapping area ova 2 , a third overlapping area ova 3 , a fourth overlapping area ova 4 , a fifth overlapping area ova 5 , and a sixth overlapping area ova 6 .

In case of the curved display panel 1000 according to the comparative example of the inventive concept, the first and second liquid crystal molecules are pre-tilted at the same pre-tilt angle on the second overlapping area ova 2 . Thus, an optical axis direction of the liquid crystal layer 1 c on the second overlapping area ova 2 is substantially parallel to an eighth liquid crystal alignment direction DR 8 that is the sum of the first and second liquid crystal alignment directions DR 1 and DR 2 . Similarly, an optical axis direction of the liquid crystal layer 1 c on the fifth overlapping area ova 5 is substantially parallel to a tenth liquid crystal alignment direction DR 10 that is the sum of the third and fourth liquid crystal alignment directions DR 3 and DR 4 .

The curved display device 1000 according to the comparative example of the inventive concept may also include lower polarization plate pol 1 and upper polarization plate pol 2 . Here, a first transmission axis pa 1 of the lower polarization plate pol 1 and a second transmission axis pa 2 of the upper polarization plate pol 2 are perpendicular to each other. For example, when the first transmission axis pa 1 of the lower polarization plate pol 1 is parallel to the ninth direction D 9 , the second transmission axis pa 2 of the upper polarization plate pol 2 is parallel to the eighth direction D 8 . The eighth direction D 8 may be parallel to the eighth liquid crystal alignment direction DR 8 or the tenth liquid crystal alignment direction DR 10 .

Thus, when the driving voltage is applied to apply the electric fields in the curved display panel 1000 according to the comparative example of the inventive concept, the optical axis direction of the liquid crystal layer 1 c within the second and fifth overlapping areas ova 2 and ova 5 may be parallel to a direction of the first transmission layer pa 1 of the lower polarization plate pol 1 or the second transmission layer pa 2 of the upper polarization plate pol 2 .

When the direction of the first transmission axis pa 1 of the lower polarization plate pol 1 is parallel to the optical axis direction of the liquid crystal layer 1 c within each of the second and fifth overlapping areas ova 2 and ova 5 , light passing through the lower polarization plate pol 1 may be blocked by the second transmission axis pa 2 of the upper polarization plate pol 2 after passing through the second and fifth overlapping areas ova 2 and ova 5 .

Also, when the direction of the second transmission axis pa 2 of the upper polarization plate pol 2 is parallel to the optical axis direction of the liquid crystal layer 1 c within each of the second and fifth overlapping areas ova 2 and ova 5 , light passing through the lower polarization plate pol 1 may be blocked without passing through the second and fifth overlapping area ova 2 and ova 5 . Thus, the user may see light of the second and fifth overlapping areas ova 2 and ova 5 .

That is, in the curved display panel 1000 according to the comparative example of the inventive concept, the first liquid crystal molecules on the lower alignment areas 1 _aa 1 , l_aa 2 , l_aa 3 , l_aa 4 of the second alignment layer al 2 and the first liquid crystal molecules on the upper alignment areas u_aa 1 , u_aa 2 , u_aa 3 , and u_aa 4 of the first alignment layer al 1 are aligned in the same direction. Thus, when the first and second substrates are curved, the user does not see light to cause texture defects by which the light is darkly seen within the pixel.

On the other hand, according to the curved display device according to the embodiment of inventive concept, which is described with reference to FIGS. 10A to 10F , the pre-tilted degrees of the first and second liquid crystal molecules are different from each other by the first and second alignment layers. Thus, even though the curved display device is curved, the texture defects may not occur to improve the display quality of the curved display device.

Although the exemplary embodiments of the present invention have been described, it is understood that the present invention should not be limited to these exemplary embodiments but various changes and modifications can be made by one ordinary skilled in the art within the spirit and scope of the present invention as hereinafter claimed.