Stock material or miscellaneous articles – Liquid crystal optical display having layer of specified...
Reexamination Certificate
2000-11-29
2004-04-20
Zacharia, Ramsey (Department: 1773)
Stock material or miscellaneous articles
Liquid crystal optical display having layer of specified...
C428S001600, C428S212000, C428S220000, C428S412000, C428S421000, C428S447000, C428S474400, C428S480000, C428S500000, C428S522000, C428S532000, C525S050000
Reexamination Certificate
active
06723392
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a light-scattering sheet (film) for liquid crystal devices useful for the high-luminance display of images, a method of producing the sheet, a light-scattering composite sheet utilizing said sheet, a liquid crystal display device, and a method of producing said light-scattering composite sheet.
BACKGROUND ART
The liquid crystal display (LCD) device is utilized broadly in the display segments of personal computers, word processors, LC televisions, chronometers, desktop calculators and other electrical and electronic products. Since the liquid crystal by itself does not emit light, a backlight for illuminating the liquid crystal cell from the back side is used in liquid crystal display devices to the exclusion of low-luminance applications such as watches and desktop calculators.
Recent years have witnessed advances in the construction of infrastructures for telecommunications systems such as internets and in the network consolidation of information through the computer-communications equipment integration. By network consolidation, the access to information is freed from restrictions as to time and place. For an efficient utilization of such networks, portable information terminals such as PDA (personal digital assistance) have recently been developed. Moreover, in lieu of notebook-sized personal computers, further-downsized mobile personal computers of reduced thickness and weight are under development.
Since portability is required of these devices, it is necessary to reconcile the need for a longer battery operating time with the need for reduced thickness and downsizing of communications devices. Therefore, display devices for use in such portable telecommunications equipment must be of reduced thickness, reduced weight and low power consumption. Particularly for attaining the low power consumption goal, a technology for brightening the display screen by exploiting natural light has been sought for replacing the conventional technology using a backlight. The display mode which is considered to be most promising is a reflecting liquid crystal display device. Particularly, to keep abreast with the increasing versatility of data accompanying the ever-continuing advances in multimedia, there is a demand for reflecting-mode liquid crystal display devices not only capable of color display and high image-quality (high-definition) display but also of low production cost.
As the reflecting liquid crystal display device, there is known a variety of devices such as TN (twisted nematic) and STN (super twisted nematic) devices but for color display and high-definition display, devices utilizing a polarizer (one polarizer plate type) is preferred. For example, the R-OCB mode in which the liquid crystal layer is of the HAN (hybrid aligned nematic) alignment has excellent characteristics such as low voltage, wider viewing angle, high-speed response, middle color rendition and high contrast. As the display device capable of forming a high-definition image on the screen, active matrix type liquid crystal display devices such as TFT (thin film transistor) which control all pixels each independently are also generally available. However, TFT and other active matrix type liquid crystal display devices must be fabricated using glass substrates because hundreds of thousands or more transistors must be formed on a substrate. In contrast, STN (super twisted nematic) liquid crystal display devices which perform matrix image displays using bar electrodes are inexpensive as compared with TFT devices and, in addition, plastic substrates can be used as the substrates for electrodes (support plates) and reflecting-mode plastic LCDs can be fabricated.
In the reflecting type LCD, the brightness of the screen is insured in such a manner that the light incident on the liquid crystal layer (natural light, ambient light) is efficiently taken in and reflected with a reflector and the reflected light is appropriately scattered (for the prevention of total reflection). When a sufficient brightness level cannot be obtained, depending on the environment of use, even if the natural or ambient light is fully exploited, a front light is at times used for supplying light from the side of the display screen of the LCD. As the reflector, a light-reflecting back electrode system utilizing light reflective electrodes and a laminate sheet such that a reflecting film has been laminated on the surface of the electrode-carrying substrate can be employed. For example, in Japanese Patent Application Laid-Open No. 22887/1998 (JP-63-22887A) and Photofabrication Symposium '92 sponsored by the Japanese Society of Printing, the fundamental technology about reflecting type LCD and the liquid crystal device given an enlarged viewing angle through the prevention of total reflection by means of a surface-corrugated metal thin film as the back electrode (lower electrode) were introduced. Such a reflecting liquid crystal display device is designed to scatter light for avoiding specular reflection and for this purpose, it includes a reflector (or a light-reflecting back electrode) whose surface has been appropriately roughened. However, it requires an elaborate processing technique and a high cost. Moreover, when the display is to be a color display, a color filter is used in addition to said polarizer. In case a color filter is used, the proportion of loss of reflected light is increased and the above diffusion plate system cannot impart enough brightness to the display screen. In the color system, it is particularly important to impart high luminance by directing diffused light in a given direction (directed diffusion). In order to increase this directionality with the diffusion-reflector system, it is necessary to precisely control the geometry and distribution pattern of reflector surface irregularities but this is a costly procedure.
For the purpose of insuring a high luminance by scattering reflected light, there has been disclosed a technology in which, in lieu of a light-diffusing reflector, the liquid crystal layer is constituted as a dispersed structure such that the liquid crystal and a high polymer are interdispersed (Japanese Patent Application Laid-Open No. 258624/1994). Also known is a liquid crystal display device in which a transmitting type light-scattering sheet is used in lieu of a diffuser plate.
For example, a technology comprising forming a light-scattering transparent resin layer either internally or externally of a liquid crystal cell is known. As an example of the display device having a light-scattering layer within the liquid crystal cell, Japanese Patent Application Laid-Open No. 98452/1995 (JP-7-98452A) discloses a display device comprising a transparent resin layer (light-scattering layer) containing a dispersion of fine particles as interposed between the electrode and substrate sheet (electrode-supporting substrate) of the electrode plate. Moreover, Japanese Patent Application Laid-Open No. 318926/1995 (JP-7-318926A) discloses a display device comprising a support plate carrying a transparent electrode, a liquid crystal layer, and as interposed therebetween, a diffusion layer comprising randomly oriented liquid crystalline polymer molecules. Meanwhile, Japanese Patent Application Laid-Open No. 261171/1995 (JP-7-261171A) discloses a display device having a light diffusing layer externally of a liquid cell, specifically a display device comprising a polarizer film on the outer surface of an electrode plate and, as formed on the surface of said polarizer film, a light-scattering layer comprising a phase-separated dispersion of two or more kinds of resins varying in refractive index. Japanese Patent Application Laid-Open No. 8430/1986 (JP-61-8430B) discloses a liquid crystal display device comprising a polarizer layer formed on the front side of a liquid crystal cell and, as formed thereon, a light-scattering layer. However, the polarizer plate usually has a highly sophisticated surface hardness characteristic and an adequate anti-glare characteristic. There
Hiraishi Masanori
Jinnai Hiroshi
Nishida Yoshiyuki
Takahashi Hiroshi
Takemoto Hiroyuki
Daicel Chemical Industries Ltd.
Zacharia Ramsey
LandOfFree
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