Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2002-04-03
2004-01-13
Font, Frank G. (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S117000, C349S114000
Reexamination Certificate
active
06678026
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device of a reflective type or a semi-transparent reflective type, which eliminates blurring of patterns on the display, and thus is able to provide a bright and sharp display, and an electronic apparatus comprising such a liquid crystal device.
2. Description of the Related Art
Many liquid crystal display devices which consume small amounts of electrical power are used as display sections in various types of electronic apparatus, such as notebook type personal computers, portable type game machines, electronic notebooks and the like. In particular, in recent years, accompanying the variety display contents, the demand for liquid crystal display devices which are capable of providing display in color is increasing. Furthermore, due to the requirement for lengthening of the battery operation time of the electronic apparatus, color liquid crystal display devices have been developed of a reflective type which do not require any back light device.
Outlines of examples of the structure of color liquid crystal display devices of prior art reflective types will now be described below with reference to the figures.
FIGS. 34A and 34B
are enlarged outline sectional figures showing the essential elements of prior art reflective type color liquid crystal display devices. Among these figures,
FIG. 34A
shows a reflective type liquid crystal display device of a frontal scattering plate type, while
FIG. 34B
shows a liquid crystal display device of an internal reflection scattering plate type.
In the liquid crystal display device of the frontal scattering plate type shown in
FIG. 34A
, a liquid crystal layer
102
is sandwiched between a pair of glass base plates
100
and
101
, and a color filter
104
is provided upon a surface portion on the liquid crystal layer
102
side of one glass base plate
101
(the upper one in the figure), while a light reflective layer
103
is provided upon a surface portion on the liquid crystal layer
102
side of the other glass base plate
100
(the lower one in the figure). Furthermore, for example, a frontal scattering film
105
in which metallic oxide particles are scattered as a filler in a base material made of triallylcyanate or the like of a thickness of 50 to 200 &mgr;m is adhered upon the upper surface side of the glass base plate
101
via a transparent adhesive material or an adhesive sheet (not shown in the figure), and a polarization plate
106
is provided over this.
With this reflective type liquid crystal device of the frontal scattering type, an incident light L
1
, after having passed through the polarization plate
106
, the frontal scattering film
105
, the glass base plate
101
, the liquid crystal layer
102
, and the color filter
104
, is reflected by the surface of the light reflective layer
103
which also serves a drive electrode, and the reflected light is emitted from the liquid crystal device via the liquid crystal layer
102
, the color filter
104
, the glass base plate
101
, the frontal scattering film
105
, and the polarization plate
106
, so as to be visible to the observer E as reflected light L
2
. Here, the light which is emitted from the liquid crystal device is controlled by the state of the liquid crystal layer
102
. In other words, the polarization state of the reflected light is controlled by the alignment state of liquid crystal molecules in the liquid crystal layer
102
, and, when the polarization state of the reflected light agrees with the polarization axis of the polarization plate
106
, the reflected light passes through the polarization plate, so that display of the desired color is performed.
Furthermore, the liquid crystal display device of the internal reflection scattering plate type shown in
FIG. 34B
comprises a pair of glass base plates
100
and
101
and a liquid crystal layer
102
, and a pixel electrode
107
made from an Al thin film or the like, which serves as a light reflective layer, is formed on the surface of the glass base plate
100
toward the liquid crystal layer
102
in a state such as to be provided with concave and convex portions which reflect light randomly. In this structure, upon the surface of the glass base plate
101
at the incident light side towards the liquid crystal layer
102
, there is provided a color filter
104
, and a polarization plate
106
is provided on the upper surface of the glass base plate
101
. In the liquid crystal display device of the internal reflection scattering plate type, an incident light, after having passed through the polarization plate
106
, the glass base plate
101
, the color filter
104
, and the liquid crystal layer
102
, is randomly reflected by the surface of the light reflective layer
107
which is formed in a concave and convex shop so as to serve as a pixel electrode, and the reflected light, after having been converted into polarized light according to the state of the liquid crystal layer
102
, passes through the color filter
104
, the glass base plate
101
, and the polarization plate
106
while being either transmitted or not transmitted by the polarization plate
106
according to its polarization state, so that, when it has been transmitted, it is visible as a color display by being incident upon the naked eye E of the observer as scattered light L
3
′.
By the way, in the prior art structure shown in
FIG. 34A
, the frontal scattering film
105
is used with the objective, when the light reflective layer
103
is a mirror reflection layer, of weakening the strong mirror reflection (regular reflection) in the particular direction which is unique to the mirror finished surface, so as thereby to enable a clear display over as wide a range as possible.
Since this type of the frontal scattering film
105
generally has a structure in which a large number of beads (with, for example, index of refraction n=1.4) of particle diameter approximately 4 &mgr;m (4×10
−6
m) are scattered in the interior of a acrylic resin layer (with, for example, index of refraction n=1.48 to 1.49 approximately) of thickness approximately 25~30 &mgr;m (25~30×10
−6
m), it is widely used in reflective type liquid crystal display devices for portable telephones, and reflective type liquid crystal display devices for portable type information apparatuses or the like.
As liquid crystal display devices for portable apparatuses, in addition to the reflective type, liquid crystal display devices of a semi transparent reflective type which comprises a back light are also known. Conventional semi transparent reflective type liquid crystal devices comprise the reflective layer being constituted as a semi transparent reflective layer. In the case of transmissive display, a transmissive display is performed by causing the light of the back light to arrive to the observer via the semi transparent reflective layer. In contrast, in the case in which the back light is not employed, this display is able efficiently to take advantage of reflected light and to function as a reflective type liquid crystal display device.
However, with the above described frontal scattering film, there is an undesirable tendency for mixing to occur between the different information in different pixels before it is perceived by the eye of the user, so that there is the problem that blurring of the pattern which is displayed on the display can easily occur. The present inventors have believed that in a reflective type liquid crystal display device such as shown in
FIG. 34A
, the pattern which is displayed on the display is blurred due to the scattering which is generated by the frontal scattering film
105
from when the incident light is reflected by the reflecting layer
103
until it reaches the eye of the user, so that, when an attempt is made to perform white display and black display upon adjacent pixels, it becomes difficult to distinguish the boundary between the white display and the black display due to the
Maeda Tsuyoshi
Okumura Osamu
Font Frank G.
Nguyen Sang H.
Seiko Epson Corporation
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