Liquid crystal cells – elements and systems – Nominal manufacturing methods or post manufacturing...
Reexamination Certificate
1999-01-26
2002-09-03
Sikes, William L. (Department: 2871)
Liquid crystal cells, elements and systems
Nominal manufacturing methods or post manufacturing...
C349S086000, C349S089000, C349S106000, C349S032000
Reexamination Certificate
active
06445438
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device (hereinafter, ref erred to as an LCD device) having wide viewing angle display characteristics, and a method for fabricating the same.
2. Description of the Related Art
Japanese Laid-Open Publication Nos. 6-301015 and 7-120728 disclose a technique of providing wide viewing angle characteristics for an LCD device. Such a technique includes steps of: dividing a liquid crystal layer into liquid crystal domains by surrounding regions thereof corresponding to pixels by a polymer wall; and aligning liquid crystal molecules in the respective liquid crystal domains in an axial symmetrical manner. Such a technique is called an axial symmetrically aligned microcell (ASM) technique. Using the ASM technique, an LCD device having a reduced change in contrast when the angle at which an observer views the LCD device changes in any direction (i.e., having wide viewing angle characteristics) is obtained.
In such an ASM mode, the control of the position of a symmetric axis (the axial position) is important. For example, as shown in
FIG. 14
, respective pixels have different axial positions
500
a
to
500
f
. When an observer views the LCD device while tilting the LCD device, the area of each pixel where the contrast changes and the area thereof where the contrast does not change vary depending on the pixels. As a result, the variation in the axial position among the pixels is observed as a difference in brightness among the pixels, thereby significantly reducing the display quality. This phenomenon is perceived by the observer as “roughness” of the screen.
Japanese Laid-Open Publication No. 8-292423 proposes a structure for overcoming the above problem, where concave portions or protrusions are formed for respective pixels for controlling the axial positions of the pixels. More specifically, an overcoat resin layer is formed on a colored layer, and a concave portion is formed on the overcoat resin layer. However, the publication does not disclose any concrete method for fabricating such a structure. The publication neither teaches nor suggests any other method for forming a concave portion other than a method for forming a concave portion on the overcoat resin layer.
Fujitsu Ltd. suggests a multi-domain vertical alignment (MVA) mode LCD device as another LCD device having wide viewing angle characteristics. The MVA mode utilizes a vertical alignment type liquid crystal cell and forms pyramid type protrusion structures on each of surfaces of a pair of glass substrates facing each other. The directions in which liquid crystal molecules fall are determined depending on respective tilted surfaces of the pyramid type protrusion structures. In other words, the directions in which liquid crystal molecules fall are not uniform over the liquid crystal cell, which enables the production of an LCD device having wide viewing angle characteristics. In the MVA mode, the protrusion structure is not necessarily disposed in the center of each pixel.
The above conventional method for fabricating the ASM mode LCD device includes several repetitions of a spin coat step and a photolithography step for forming concave portions in respective pixels. When a film is formed using the spin coat method, however, it is difficult to control the thickness of the film with high precision. Moreover, when a multilayer film is formed using the spin coat method, if a layer formed by a first spin coat step is uneven, a layer formed by a subsequent spin coat step is affected by the unevenness of the underlying layer. This further makes it difficult to control the thickness of the film with high precision. In addition, several repetition of the photolithography step (including resist application, light exposure, and development) increases the possibility of an occurrence of a factor which can reduce the yield, such as positional displacement and attachment of foreign matters. For the above reasons, in the conventional fabrication method, it is difficult to simplify the steps and suppress the production cost.
In the conventional method, a number of steps are required to form concave portions on a color filter layer substrate, thereby reducing the yield. Moreover, since colored layers constituting color filter layers are formed by the spin coat method, the thickness of the layers is not likely to be uniform, degrading the display characteristics of the color filter layers (Y value and chromaticity). In particular, when a thick layer is required, it is not possible to control the thickness over a wide area of the layer. Moreover, since an overcoat resin layer needs to be formed on each colored layer, such problems that the concave portions of respective pixels are not uniform and that the concave portions are buried within the overcoat resin, arise.
SUMMARY OF THE INVENTION
The liquid crystal display device of this invention includes a first substrate, a second substrate opposing the first substrate, and a liquid crystal layer sandwiched between the first and the second substrates, wherein the liquid crystal layer includes a polymer region and a liquid crystal domain surrounded by the polymer region in which liquid crystal molecules are oriented in an axial symmetrical manner, the first substrate includes a dry film having a concave portion on a surface facing the liquid crystal layer, and a symmetric axis in the liquid crystal domain substantially extends through the concave portion and is substantially perpendicular to the first substrate.
In one embodiment of the invention, the dry film is a colored film.
In another embodiment of the invention, the colored film is located on a colorless film having an opening.
In still another embodiment of the invention, the dry film is a colorless film, the colorless film has an opening, and the colorless film is located on a colored film.
In still another embodiment of the invention, the second substrate includes a channel portion in which a rare gas is enclosed and an anode electrode and a cathode electrode disposed inside the channel portion, and a potential difference is provided in the liquid crystal domain by applying a voltage between the anode electrode and the cathode electrode to generate plasma discharge in the channel portion.
Alternatively, the liquid crystal display device of this invention includes a first substrate, a second substrate opposing the first substrate, and a liquid crystal layer sandwiched between the first and the second substrates, wherein the liquid crystal layer includes a polymer region and a liquid crystal domain surrounded by the polymer region in which liquid crystal molecules are oriented in an axial symmetrical manner, the first substrate includes a transparent electrode having a concave portion on a surface facing the liquid crystal layer, and a symmetric axis in the liquid crystal domain substantially extends through the concave portion and is substantially perpendicular to the first substrate.
In another embodiment of the invention, the second substrate includes a channel portion in which a rare gas is enclosed and an anode electrode and a cathode electrode disposed inside the channel portion, and a potential difference is provided in the liquid crystal domain by applying a voltage between the anode electrode and the cathode electrode to generate plasma discharge in the channel portion.
According to another aspect of the invention, a method for fabricating a liquid crystal display device is provided. The method includes the steps of: forming a dry film on a first substrate; forming a concave portion on the dry film; arranging the first substrate to face a second substrate so that the concave portion of the dry film is located inside; injecting a precursor mixture of a polymerizable material and a liquid crystal material in a space between the first and second substrates; forming a polymer region and a liquid crystal domain surrounded by the polymer region in which liquid crystal molecules are oriented in an axial symmetrical manner by su
Fujii Toshio
Horie Wataru
Nagayasu Takayoshi
Chowdhury Tarifu R.
Sharp Kabushiki Kaisha
Sikes William L.
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