This application is based upon and claims the benefit of priority from a prior Taiwanese Patent Application No. 097105135, filed on Feb. 14, 2008, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The invention relates to liquid crystal display devices and fabrication methods thereof, and more particularly to horizontal-switching flexible liquid crystal displays and fabrication methods thereof.
2. Description of the Related Art
Liquid crystal display (LCD) devices have several advantages over other display technologies, such as a smaller volume, a lighter weight, and lower power consumption. As such, LCD devices are being applied in a variety of electronic and communication devices including notebook computers, personal digital assistants (PDA), mobile phones and others. Given the trends, technological development of LCD devices are now focusing on lighter and thinner profiles with increased portability.
Limitations of conventional flexible LCD devices are due to uneven deformation of a liquid crystal cell gap. When display regions are affected by applied force causing the LCD to bend, it becomes difficult for the gap of the LC cell to maintain a desirable distance. As such, phase retardation and phase difference of passing light are negatively affected, thus deteriorating display quality of conventional flexible LCD devices.
In order to solve the abovementioned problems such as applied force and retardation due to bending, U.S. Pat. No. 5,699,139, the entirety of which is hereby incorporated by reference, discloses an LCD device forming stress released structures on the edges of the display panel to release stress generated during bending of the substrate.
U.S. Pub. No. 2003/0137630, the entirety of which is hereby incorporated by reference, discloses an LCD device with a trench formed at a peripheral region of the panel. The stress is absorbed to effectively prevent variation of the LC gap.
Further, U.S. Pub. No. 2006/0204675, the entirety of which is hereby incorporated by reference, discloses a flexible LCD device. A rigid display region and a flexible bending buffer region are formed on a flexible substrate. When the substrate is bended, stress and strain are mainly concentrated on the flexible bending buffer region to prevent the rigid display region from deformation.
The conventional methods and structure for releasing stress on the flexible substrate, however, can affect structural strength. In addition, a complex and tedious fabrication process is also required, increasing production costs. Thus, flexible LCD devices, whereby LC layer gap is not affected by applied stress and the structural strength of the substrate remains unchanged, are eagerly desired.
Embodiments of the invention provide horizontal-switching flexible liquid crystal display devices. Orientations of the liquid crystal molecules (i.e., by designing more stable liquid crystal orientations) are changed so that the liquid crystal gap and phase retardation of the LC layer remain unchanged as the substrate is bended.
An exemplary embodiment of the invention provides a horizontal-switching flexible liquid crystal display (LCD) device, comprising: a first substrate and a second substrate opposing to each other with a liquid crystal (LC) layer interposed therebetween, wherein the LC layer is affected by a horizontal field and divided into an upper portion and a lower portion; at least one pair of a patterned pixel electrode and a common electrode, disposed on the first substrate, wherein the pixel electrode and the common electrode are formed on the same plane, thereby generating a horizontal field during operation; a first alignment layer disposed on the first substrate covering the pixel electrode and the common electrode; and a second alignment layer disposed on the second substrate, wherein the first and second alignment layers allow the LC molecules of the LC layer to be in a substantially vertical alignment, and wherein the phase retardation of the horizontal-switching LCD is due to the lower portion of the LC layer.
Another exemplary embodiment of the invention provides a horizontal-switching flexible liquid crystal display (LCD) device, comprising: a first substrate and a second substrate opposing to each other with a liquid crystal (LC) layer interposed therebetween, wherein the LC layer is affected by a horizontal field and divided into an upper portion and a lower portion; a common electrode disposed on the first substrate; a dielectric layer disposed on the common electrode; a patterned pixel electrode disposed on the dielectric layer, wherein the pixel electrode and the common electrode are located at different planes, thereby generating a fringe field during operation; a first alignment layer disposed on the first substrate covering the pixel electrode and the common electrode; and a second alignment layer disposed on the second substrate, wherein the first and second alignment layers allow the LC molecules of the LC layer to be in a substantially vertical alignment, and wherein the phase retardation of the horizontal-switching LCD is due to the lower portion of the LC layer.
An exemplary embodiment of the invention provides a fabrication method for a horizontal-switching flexible liquid crystal display (LCD) device, comprising: forming at least one pair of a patterned pixel electrode and a common electrode on a first substrate, wherein the pixel electrode and the common electrode are formed on the same plane; forming a first alignment layer on the first substrate covering the pixel electrode and the common electrode; forming a second alignment layer on the second substrate, wherein the first alignment layer and the second alignment layer are rubbed along an oriented direction, and an included angle between the rubbed oriented direction and the first and the second alignment layers is substantially perpendicular; assembling the first substrate and the second substrate; filling a liquid crystal layer between the first substrate and the second substrate; and sealing the liquid crystal layer.
Another exemplary embodiment of the invention provides a fabrication method for a horizontal-switching flexible liquid crystal display (LCD) device, comprising: providing a first substrate; forming an entire common electrode on the first substrate; forming a dielectric layer on the common electrode; forming a patterned pixel electrode on the dielectric layer, wherein the pixel electrode and the common electrode are formed at different planes; forming a first alignment layer on the first substrate covering the pixel electrode and the common electrode; forming a second alignment layer on the second substrate, wherein the first alignment layer and the second alignment layer are rubbed along an oriented direction, and an included angle between the rubbed oriented direction and the first and the second alignment layers is substantially perpendicular; assembling the first substrate and the second substrate; filling a liquid crystal layer between the first substrate and the second substrate; and sealing the liquid crystal layer.
The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.
Embodiments of the invention provide flexible LCD structures. Using specific orientation of liquid crystal molecules configured with a special electrode structural design, the liquid crystal layer gap of the embodiments of the invention has changed, while the phase retardation remains stable, thus maintaining stable optical performances as the display panel is bended. Specifically, a predetermined mode of liquid crystal orientations is used to fabricate an LCD device which is less sensitive to LC cell gap variations. Thus, phase retardation of passing light through the LC layer is not affected, thereby maintaining stable optical performance.
A second alignment layer 202 is disposed on the second substrate 201, wherein the first alignment layer 205 and the second alignment layer 202 allow LC molecules of the LC layer to be in a substantially vertical alignment. The driving electric field E of the horizontal-switching flexible LCD device is primarily distributed in the lower region 203b of LC layer from the pixel electrode 206 to the common electrode 207. Moreover, since the phase retardation of the horizontal-switching LCD is due to the lower portion 203b of the LC layer, phase and retardation of the lower portion 203b of the LC layer remain constant even if the LC cell gap varies due to deformation of the second substrate (upper substrate) 201.
One of the first substrate 208 and the second substrate 201 can be a flexible substrate. For example, the second substrate 201 is a flexible substrate including a polycarbonate (PC) substrate, a polyethersulfone (PES) substrate, a polyethylene terephthalate (PET) substrate, a polyimide (PI) substrate, a p-nitrophenylbutyrate (PNB) substrate, a polyetheretherketone (PEEK) substrate, a polyethylenenaphthalate (PEN) substrate, a polyetherimide (PEI) substrate, or a polyacrylate (PAR) substrate. Alternatively, both the first substrate and the second substrate can be flexible. According to an embodiment of the invention, the upper substrate is adapted to a flexible substrate such that deformation occurs at one side of the LCD panel. Since phase retardation is contributed from the other side of the LCD panel, the entity of the phase retardation remains constant regardless of variation of the LC cell gap, i.e., optical performance of the LCD device is unaffected.
The first substrate 208 can be an active matrix substrate including an array of active devices (not shown) corresponding to each pixel of the horizontal-switching LCD device 200. The second substrate 201 can be a color filter (CF) substrate, including color filter structures and a black matrix among the color filter structures. The shape of the pixel electrode 206 can be striped, square, zigzagged, serpentine, polygonal, or circular. Similarly, the shape of the common electrode 207 can be striped, square, zigzagged, serpentine, polygonal, or circular.
According to another embodiment of the invention, the first alignment layer 205 and the second alignment layer 202 are separately performed a rubbing procedure, such that liquid crystal molecules in the LC layer are substantially vertically oriented. For example, the liquid crystal molecules in the LC layer are respectively aligned to the first alignment layer and the second alignment layer in a range of about 90°±15°.
In referring to
A first alignment layer 305 is disposed on the first substrate 308 covering the pixel electrode 306, and a second alignment layer 302 is disposed on the second substrate 301. The first alignment layer 305 and the second alignment layer 302 are separately performed a rubbing procedure such that liquid crystal molecules in the LC layer are substantially vertically oriented. For example, the liquid crystal molecules in the LC layer are respectively aligned to the first alignment layer and the second alignment layer in a range of about 90°±15°.
One of the first substrate 308 and the second substrate 301 can be a flexible substrate. Alternatively, both the first substrate and the second substrate can be flexible. The first substrate 308 can be an active matrix substrate including an array of active devices (not shown) corresponding to each pixel of the horizontal-switching LCD device 300. The second substrate 301 can be a color filter (CF) substrate, including color filter structures and a black matrix among the color filter structures. The shape of the pixel electrode 306 can be striped, square, zigzagged, serpentine, polygonal, or circular.
In referring to
One or both of the first substrate 407 and the second substrate 401 can be a flexible substrate. For example, the second substrate 401 is a flexible substrate including a polycarbonate (PC) substrate, a polyethersulfone (PES) substrate, a polyethylene terephthalate (PET) substrate, a polyimide (PI) substrate, a p-nitrophenylbutyrate (PNB) substrate, a polyetheretherketone (PEEK) substrate, a polyethylenenaphthalate (PEN) substrate, a polyetherimide (PEI) substrate, or a polyacrylate (PAR) substrate.
Note that there are additional structural elements and fabrication steps not mentioned here, which are required to complete the horizontal-switching LCD device, but which are not essential to an understanding of the invention. For simplicity, detailed description is omitted.
While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
Number | Date | Country | Kind |
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TW097105135 | Feb 2008 | TW | national |