Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
1997-11-19
2004-08-24
Nguyen, Dung (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S139000, C349S143000
Reexamination Certificate
active
06781652
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display panel which is equipped to a word processor, personal computer or other electronic devices, and a method for manufacturing a light reflecting film of the liquid crystal display panel.
More particularly, the invention concerns a liquid crystal display panel which is of a reflection type wherein display is made by reflecting light having entered from the outside without using a back-light and which is small in power consumption, and a method for manufacturing a light reflecting film of the liquid crystal display panel.
2. Description of the Related Art
As a liquid crystal display panel there are a twisted nematic type which darkens due to the presence of two polarizing plates although it can have a high contrast, a super twisted nematic type which can have a high contrast and be driven in a simple way, a phase transition type guest/host type which is high in luminance and less in parallax error because of no need to use a polarizing plate, etc.
In the above-mentioned phase transition type guest/host liquid crystal, dichroic pigment is added to and mixed with the guest molecules in the host liquid crystal and, by varying the arrangement of the liquid crystal molecules by means of the voltage applied to the liquid crystal, the light absorptance of the liquid crystal layer is varied.
FIG. 5
is a typical view of a conventional example, illustrating the section of one pixel of a liquid crystal display panel using a phase transition type guest/host liquid crystal.
In
FIG. 5
, between an active matrix substrate
51
and an opposing substrate
52
, there are formed sequentially from an upper surface of the active matrix substrate
51
thin film transistors
53
, interlayer insulating film
54
, pixel electrodes
55
, light reflecting films
56
formed on the surface of the pixel electrodes, orientation film
57
, phase transition type guest/host liquid crystal
58
, orientation film
59
, opposing electrode
60
, and color filter
61
in this order.
Since
FIG. 5
is intended to illustrate one pixel, the whole of the liquid crystal display panel is not illustrated therein. However, on the upper surface of the active matrix substrate
51
, the thin film transistors
53
corresponding to a numeric value three times as large as the number of the pixels are formed in the form of a matrix. On the upper surface of the active matrix substrate
51
, the pixel electrodes
55
corresponding to a numeric value three times as large as the number of the pixels are formed by being insulated by the interlayer insulating film
54
.
In the above-mentioned liquid crystal display panel, incident light
62
having entered from the outside transmits through the opposing substrate
52
, color filter
61
, opposing electrode
60
, orientation film
59
, phase transition type guest/host liquid crystal
58
and orientation film
57
and then is reflected by the light reflecting film
56
, whereupon the resulting light advances through a path opposite to that through which the incident light entered and goes outside, thus becoming a reflected light
63
.
Also, the pixel electrode
55
is made of aluminum and is provided with fine concavities and convexities in order to scatter and reflect the light having entered thereinto by its surface. And, the concavities and convexities of the pixel electrode
55
are so designed that the light having entered from a direction inclined by an angle of 30° with respect to the direction orthogonal to the pixel electrode
55
may be strongly reflected in this direction orthogonal thereto.
And, the surface of the pixel electrode
55
is chemically formed with the concavities and convexities by etching which uses acid, such as hydrofluoric acid treatment, thereby constituting the light reflecting film
56
.
Between the opposing electrode
60
and the pixel electrode
55
there is sealed the phase transition type guest/host liquid crystal
58
. In its natural state, the phase transition type guest/host liquid crystal
58
is such that the host liquid crystal molecules are helically arranged. In a state where a voltage is applied thereto, the helicoid is released with the result that the molecules are arranged vertically with respect to the opposing substrate
52
. For this reason, the phase transition type guest/host liquid crystal
58
makes it possible to obtain a high contrast without using a polarizing plate.
However, whereas the phase transition type guest/host liquid crystal enables the procurement of a high contrast with no use of a polarizing plate, when driving it the application of a high voltage was needed for releasing the helicoid.
Accordingly, because of its large power consumption, the phase transition type guest/host liquid crystal had the problem that when it was applied to portable electronic devices, the time period in which a battery was used therein was short.
Also, in the pixel electrode of the phase transition type guest/host liquid crystal, time and labour were needed to perform the treatment for producing the light reflecting film whose concavities and convexities causing uniform scatter of light have been formed by etching.
Also, in the fabrication of the light reflecting film having concavities and convexities by etching, there was a limitation with respect to enlarging the depth of the concavities and convexities and so the scattering of light was not sufficient, the resulting structure therefore having a problem with the brightness demanded of the liquid crystal display panel.
Further, while electronic devices are for the most part arranged to reflect light, which is incident thereupon from a direction inclined by an angle of 30° with respect to the direction orthogonal thereto, in this direction orthogonal thereto, there are also electronic devices such as televisions which are wanted to be viewed by a plurality of persons or electronic devices such as wrist watches in which it is better to reflect the incident light from the orthogonal direction in this orthogonal direction. With regard to the light reflecting film of the liquid crystal display panel used in the electronic devices, it was difficult to control the configuration of the concavities and convexities so as to enable the uniform reflection of light whose incident angle was different.
SUMMARY OF THE INVENTION
The present invention has been made in order to solve the above-described problems and an object of the present invention is to provide a liquid crystal display panel whose image plane is high in luminance, by making up the light reflecting film into a porous layer and thereby making the light to be scattered large in amount.
Another object of the present invention is to provide a method for manufacturing the light reflecting film of the liquid crystal display panel, which enables the simple control of the configuration of the porous layer by subjecting the light reflecting film to anodic oxidation.
To attain the above objects, according to a first aspect of the present invention, the liquid crystal display panel according thereto uses a phase transition type guest/host liquid crystal shown in FIG.
1
. It comprises pixel electrodes
15
disposed on an active matrix substrate
11
in the form of a matrix with an interlayer insulating film
14
therebetween and respectively connected to thin film transistors
13
and light reflecting films
16
formed in an upper surface of the pixel electrodes, the light reflecting films consisting of a porous layer.
According to a second aspect of the present invention, the light reflecting film of the liquid crystal display panel of the present invention is arranged such that the porous layer of the same configuration is multilayered.
According to a third aspect of the present invention, the light reflecting film of the liquid crystal display panel of the present invention is arranged such that the porous layer of a different configuration is multilayered.
According to a fourth aspect of the present invention, the liquid crystal display pa
Fish & Richardson P.C.
Nguyen Dung
Semiconductor Energy Laboratory Co,. Ltd.
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