Patent Application
20060170843
The present invention relates to liquid crystal display (LCD) devices, and more particularly to a reflection type LCD device.
Among LCD products, there have been the following three types of LCD devices commercially available: a reflection type LCD device utilizing ambient light, a transmission type LCD device utilizing backlight, and a semi-transmission type LCD device equipped with a half mirror and a backlight.
The reflection type LCD has been widely used as a portable display device such as in an electronic calculator or a personal digital assistant (PDA), because this type of LCD does not require a backlight and has low power consumption.
As shown in
The liquid crystal layer 15 includes a plurality of liquid crystal molecules (not labeled) of the twisted nematic (TN) type. The molecules align according to an electric field generated when a voltage is applied.
However, the reflection type LCD 10 has the following problems. The TN type molecules have a slow response time and may take unduly long to display images. In addition, the viewing angle characteristics of the reflection type LCD 10 may not be wide enough to meet the desired standards for a modern, high quality display.
What is needed, therefore, is a liquid crystal display device that overcomes the above-described deficiencies.
In a preferred embodiment, a reflective liquid crystal display (LCD) device includes a first substrate and a second substrate. A liquid crystal layer having liquid crystal molecules is interposed between the first and second substrates. The liquid crystal molecules are bend-aligned to cause the reflective liquid crystal display device to operate in an optically compensated bend (OCB) mode. A first alignment layer and a second alignment layer are respectively disposed between the liquid crystal layer and the first and second substrates.
The reflective LCD device preferably further includes a first retardation film and a second retardation film both disposed at an outer surface of the first substrate.
According to another embodiment, the reflective LCD device may further include a compensation layer disposed between the first retardation film and the first substrate.
In certain of various embodiments of the reflective LCD device, one or more retardation films and the compensation layer can compensate for color, with the compensation layer also improving the viewing angle. This helps ensure that the reflective LCD device provides a good quality display image. In addition, the alignment and a pretilt angle of the liquid crystal molecules ensure that the liquid crystal molecules realign in a very short time upon a change in a driving electric field.
Other advantages and novel features will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.
A first alignment layer 231 and a reflection electrode 241 are disposed between the liquid crystal layer 25 and the first substrate 21. A second alignment layer 232 and a common electrode 242 are disposed between the liquid crystal layer 25 and the second substrate 22. A polarizer 26 is disposed at an outer side of the second substrate 22. The liquid crystal molecules are bend-aligned so that the reflective LCD device 20 operates in an optically compensated bend (OCB) mode. A pretilt angle of the liquid crystal molecules adjacent to the substrates 21 and 22 is in a range of 0° to 15°. The reflection electrode 241 is made of metal with a high reflective ratio, such as aluminum (Al). The common electrode 242 is made of a transparent conductive material, such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO).
A retardation film 271 is disposed between the polarizer 26 and the second substrate 22. The retardation film 271 is a quarter-wave plate.
The liquid crystal molecules in the reflective LCD device 20 are bend-aligned to have a pre-tilt angle, which ensures that the liquid crystal molecules can more easily adjust their orientation when a voltage is applied to the reflective LCD device 20 and a change in a driving electric field is effected. Thereby, the reflective LCD device 20 has a fast response time. Moreover, the retardation film 271 facilitates the reflective LCD device 20 to display a good quality image.
Liquid crystal molecules in the reflective LCD device 40 are bend-aligned to have a pre-tilt angle, which ensures that the liquid crystal molecules can more easily adjust their orientation when a voltage is applied to the reflective LCD device 40 and a change in a driving electric field is effected. Thereby, the reflective LCD device 40 has a fast response time. Moreover, the retardation films and the compensation layer 48 are used for compensating for color, so as to ensure that the reflective LCD device 40 displays a good quality image.
Various modifications and alterations of the above-described embodiments are possible. For example, the compensation layer may be a biaxial compensation film, a single compensation film, an A-plate compensation film, or a discotic molecular film. In addition, the LCD device may employ a single compensation layer at the first substrate instead of at the second substrate. Furthermore, any one or more or all of the retardation films and the compensation layer may be disposed on or at inner surfaces of either of the first and/or second substrates.
It is to be further understood that even though numerous characteristics and advantages of the present embodiments have been set out in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 94102622 | Jan 2005 | TW | national |
