Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2000-06-23
2003-05-06
Ton, Toan (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
Reexamination Certificate
active
06559905
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-179214, filed Jun. 25, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to an active matrix substrate for a liquid crystal display device and a method of manufacturing the same.
Liquid crystal display devices (LCD) are advantageous since they are formed thin and display color images with low power consumption. By virtue of these advantages, the LCDs are widely used for lap-top personal computers. The image quality of the LCDs is good enough to be employed not only for electric-data display devices but also for TV screens.
Of the LCD devices, an active matrix type LCD is used as a flat panel display capable of providing full-color images with a high quality. The active matrix type LCD is formed of a first glass substrate, a second glass substrate and liquid crystal which is injected between the first and the second glass substrate. In the first glass substrate, thin transistors (TFT), which employ amorphous silicon or poly crystalline silicon as an active layer, are arranged in a matrix form. The second glass substrate is fixed so as to face the first glass substrate with a gap of about 5 &mgr;m interposed between them.
FIG. 1
shows a cross-sectional view of a pixel portion of a conventional active matrix type LCD.
A scanning line
3502
and a storage capacitor line
3503
are formed on a glass substrate
3501
. A gate insulating film
3504
is formed over the lines
3502
and
3503
. Furthermore, a pixel electrode
3505
is selectively formed on the gate insulating film
3504
.
Reference numeral
3506
is a TFT portion, which is formed of a semiconductor layer
3507
, a channel protecting insulating film
3508
formed on the semiconductor layer
3507
, and two doped semiconductor layers
3509
facing each other. The two doped semiconductor layers are formed in contact with the semiconductor layer
3507
while an end portion of each of the doped semiconductor layers is mounted on the channel protecting insulating film
3508
. A source electrode
3510
and a drain electrode
3511
are formed respectively on the two doped semiconductor layers
3509
. The source electrode
3510
is connected to a signal line (not shown). The drain electrode
3511
is connected to the pixel electrode
3505
. A protective insulating film
3512
is formed over the TFT portion
3506
.
With recent technical development, a field of view has been widened. Accordingly, a narrow viewing angle of the LCD has been overcome. In addition to this, since the TFT array can be formed on the glass substrate, a relatively large display having a diagonal length of about 10 to 25 inches has been realized.
However, to realize a high definition TV (HDTV), a large screen having a diagonal length of about 40-60 inches is desired. To manufacture the TFT array for such a large screen, it is necessary to construct an assembly line capable of holding an ultra-large glass substrate larger than 1 m square. A large equipment cost is inevitably required.
A method of making the large screen by jointing a plurality of substrates carrying TFT arrays is disclosed in Japanese Patent Applicaltion KOKAI publication No. 10-268332. However, this method has the following problems. Since the substrates are not jointed accurately, an aperture ratio of the joint portion is low. It is difficult to accurately control the level of the joint portion between the substrates, taking the thickness (5 &mgr;m) of the liquid crystal layer into consideration. Therefore, a large quantity of the substrates are not manufactured.
On the other hand, a mobile data terminal equipment providing electronic data anytime and anywhere was developed by making use of “low power consumption” of the LCD. The mobile data terminal equipment has been used in a wide variety of fields. In future, it is expected that electronic data will be displayed with the same ultra precision as that of printing matter, that is, about 150-300 pixel/inch (ppi).
These mobile data terminal equipments have to be formed light with a low power consumption. When a liquid crystal display is formed on an A4-size glass substrate of about 0.7 mm-thick, the total weight of the display results in 220 g. If the weight of the bezel for fixing the display is included, the total weight of the device will be about 400 g or more.
The weight of the display device can be reduced by about ½ if a plastic substrate is employed. The weight can be further reduced, if a film substrate is used. Such a display device is suitable for use in the mobile data terminal equipment. In these circumstances, attempts have been made to form the TFTs on the plastic substrate or the film substrate. When the TFTs are formed on these substrates, however, it is necessary to reduce the processing temperature. If the TFTs are formed at a low processing temperature, performance of the TFTs may be degraded, with the result that limitations may be imposed on image quality and the number of pixels. Furthermore, the thermal expansion coefficiency of these substrates is high and plastic deformation occurs at a low temperature. For these reasons, it is conceivable that the high definition display device may not be attained.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide an active matrix substrate for achieving the formation of a high definition image at a low cost even if a large substrate or a non-glass substrate is used, and also provide a method for manufacturing the same.
According to a first aspect of the present invention, to attain the aforementioned objects, there is provided a method of manufacturing an active matrix substrate comprising:
a first step of forming a plurality of elements on a first substrate;
a second step of forming wirings on a second substrate;
a third step of transferring some elements selected from the plurality of elements onto the second substrate from the first substrate; and
a fourth step of selectively connecting the some elements transferred onto the second substrate to the wirings.
According to a second aspect of the present invention, there is provided a method of manufacturing an active matrix substrate comprising:
a first step of forming a plurality of elements on a first substrate;
a second step of transferring some elements selected from the plurality of elements onto a second substrate from the first substrate;
a third step of forming wirings on the second substrate after the second step; and
a fourth step of selectively connecting the some elements and the wirings.
In the methods of manufacturing an active matrix substrate according to the first and second aspects, it is preferable that the following steps be carried out.
The third step includes the steps of:
adhering the plurality of elements formed on the first substrate onto the third substrate;
etching away the first substrate; and
transferring the some elements selected from the plurality of elements adhered on the third substrate to the second substrate.
The third step includes the steps of:
forming an adhesion layer on the third substrate;
transferring the plurality of elements formed on the first substrate onto the third substrate via the adhesion layer; and
selectively heating portions of the adhesion layer on which the some elements are formed, to thereby transfer the some elements from the third substrate to the second substrate.
In the aforementioned step, the elements may be removed from the element formation substrate by laser irradiation in place of heat application. Alternatively, the elements formed on the element formation substrate may be transferred on the adhesion layer which is heated and further transferred from the intermediate transfer substrate to the final substrate by UV irradiation.
The third step includes a step of selecting the some elements such that a largest interval of two adjacent elements arbitrarily chosen from the some elements is large
Nguyen Hoan
Ton Toan
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