Substrate of electrode for liquid crystal

Details Substrate of electrode for liquid crystal Substrate of electrode for liquid crystal

1996-08-19

1998-10-06

Thomas, Alexander

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

With charge transferring layer of specified composition

349158, G02F 11343

Patent

active

058173838

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELDS

The present invention relates to a substrate of electrode for liquid crystal which comprises a substrate film for liquid crystal and a transparent electrode. More particularly the present invention relates to a substrate of electrode for liquid crystal which employs an aromatic polyester or a polycarbonate containing the particular bisphenol component, as a substrate film for liquid crystal.


BACKGROUND ART

In recent years, electronic instruments are more and more downsized. Liquid crystal displays have been used widely as display portions of lap-top-type personal computers, word processors, portable information instrument terminals, and the like, by making the best use of their features such as lightness, compactness and low energy consumption. As substrate of the transparent electrode for elements of liquid crystal display, though glass has been conventionally used, the use of plastic substrates is now being studied in view of their features such as breakage resistance and lightness.
In case that plastic films are used as the substrates of the transparent electrodes, one of their drawbacks is a low heat resistivity. Namely, in order to obtain high reliability of finally assembled cell, it is necessary to heat up to around 150.degree. C. in the step of assembling the liquid crystal cell, e.g. applying and drying of an orientated membrane and sealing of the cell. Also, for portable instruments, wide liquid crystal displays have been increasingly used, and the STN display has been used in addition to the TN-type display. As for the STN, a phase differential film is used to cancel coloring trouble. If the phase differential film and a transparent electrically conductive film can be integrated, the construction can be conveniently simplified. However, in this case, if the films do not have a particularly higher heat resistance, the products cannot be used because restoration of retardation occurs at the time of assembling of the liquid crystal cell.
Further, when using as substrate films for liquid crystal, the contrast turns bad if a substrate having a low retardation is not used. The retardation is represented by a product of a film thickness d and a birefringence .DELTA.n. Such films are obtained by melt extrusion or solution casting. As the substrate film, one having good surface properties is desirable, and for this purpose, it is desirable to be produced according to the solution casting. The retardation is, however, raised when a certain tension is applied during the drying step of the casted film.
Also, at the time of the cell assembling, sealing is achieved around the cell by using adhesives under heating, and, in some cases, with respect to the above-mentioned substrate film of electrode for liquid crystal, there remains a tension therein due to heat-shrinkage, so that the retardation sometimes appears. When the retardation appears, it is not preferable since the contrast of the liquid crystal cell fades away. Accordingly, preferred materials are those in which retardation is not increased even when a tension applies thereto.
For these requirements, polyethylene terephthalate or polycarbonate is proposed as a material of the plastic substrate film (Y. Umeda, T. Miyashita, and F. Nakano, "Liquid Crystal Plastic Substrates" p. 178, in SID Simp. Dig. Tech. Papers, P. 178, 1982).
However a usual biaxally-orientated film of polyethylene terephthalate has a strict orientation, and thus cannot be used for the liquid crystal cell, since color development happens at the time when inserted between polarizing plates. Also, when using a uniaxially-orientated film of polyethylene terephthalate for avoiding this trouble, it is necessary to conform the optical axis to that of the polarizing plate, and further since its heat resistance is below 100.degree. C., the processing step of cell assembling can take place only under remarkably specific conditions.
On the other hand, with respect to the polycarbonate for the substrate film for liquid crystal, a usual bisphenol A type polycarbonate has bee

REFERENCES:
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patent: 5041521 (1991-08-01), Serini et al.
patent: 5086159 (1992-02-01), Fritsch et al.
patent: 5126428 (1992-06-01), Freitag et al.
patent: 5227458 (1993-07-01), Freitag et al.
Patent Abstracts of Japan, vol. 13, No. 322 (P-902), 20 Jul. 1989, and JP 01 090418, 6 Apr. 1989.

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