Chip card with a bistable display

Details Chip card with a bistable display Chip card with a bistable display

2000-05-30

2002-04-16

Wu, Shean C. (Department: 1756)

Stock material or miscellaneous articles

Liquid crystal optical display having layer of specified...

C252S299010, C235S380000, C345S087000, C345S098000

Reexamination Certificate

active

06372307

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The term “chip card” is taken to mean a card, usually made of plastic and in credit card format, provided with an integrated circuit which is capable of storing and/or processing information electronically, and means for information transmission between the card and an electronic read and/or write system
A smart card is a chip card which contains additional means for checking/controlling access to the card. For example, these means can be an integrated circuit which controls who uses the stored information and for what purpose. This enables data security to be increased.
Chip cards or smart cards are already in widespread use, for example as telephone cards, credit cards, “medicards”, cash cards, and as identity cards for access control.
In the near future, it is expected that this technology will penetrate further into areas such as the “electronic wallet”, i.e. replacement of cash, travel tickets and pay TV.
A desirable feature for chip cards, and one that has already been proposed, is a permanent, visible electronic display on the card which provides information, for example on the amount stored, the amount remaining and date information.
Such a display should be legible even without application of an electric voltage, since neither the thickness nor the production costs of a card allow the installation of a battery. The display must thus be capable of optical storage.
2. Description of the Related Art
For reasons of optical bistability, surface-stabilized ferroelectric liquid-crystal Displays (SSFLCDs) and bistable nematic displays (see E. Lüder et al., 1997 International Symposium, Seminar & Exhibition, Society of Information Display, Boston, Mass., Abstract 9.4, SID 97 DIGEST, pp. 109-112) and surface- and polymer-stabilized cholesteric textures (SSCT or PSCT) have been proposed for such applications.
SSFLCDs are already being used in computer displays, but use in chip cards requires a significantly different property profile, covering, for example in accordance with ISO 7816, compressive strength, impact resistance, flexibility, a low addressing voltage of preferably ≦5 volts, legibility in daylight and in particular low thickness and weight in addition to optical storage capability.
There is therefore a high demand for SSFLCD displays or ferroelectric liquid-crystal mixtures (FLCs) for such displays which, in particular, are up to the demands made of chip cards or smart cards.
Surprisingly, it has now been found that ferroelectric liquid-crystal mixtures having low optical anisotropy (An) values are particularly suitable for use in ferroelectric liquid-crystal (FLC) displays for chip cards.
SUMMARY OF THE INVENTION
The invention therefore relates to a chip card containing a ferroelectric liquid-crystal display containing ferroelectric liquid-crystal layer, wherein the liquid-crystal layer has optical anisotropy values of ≦0.15 in the region of the operating temperature.
DETAILED DESCRIPTION OF THE INVENTION
The chip card according to the invention is particularly practicable since the display can be switched at voltages ≦15 V, generally ≦5 V. It can be written in a broad temperature range and is robust to everyday loads, such as pressure, flexing or thermal deformation.
The display used according to the invention has a high switching angle, a low switching voltage and low temperature dependence. Defect lines can be suppressed. No zig-zag deformations occur, or if they do, they are of such low magnitude that they are unimportant.
The chip card according to the invention is preferably a smart card.
The optical anisotropy is preferably from 0.05 to 0.15, particularly preferably from 0.08 to 0.14, very particularly preferably from 0.10 to 0.14, especially from 0.11 to 0.14, in the temperature region of the operating temperature of the liquid-crystal display. The region of the operating temperature is defined by the operating temperatures of the read/write equipment and is thus generally between −10 and 40° C.
The tilted smectic, optically active (ferroelectric) liquid crystal (FLC) preferably consists of a mixture of low-molecular-weight compounds of the formula (I) given below and possibly further mixture components. The working phase is a chiral tilted phase, preferably the S
c
* phase. The mixtures preferably comprise a non-optically active base mixture, preferably in a proportion of >50%, and one or more optically active compounds (dopants), which may themselves be liquid-crystalline, but need not be liquid-crystalline.
The spontaneous polymerization of the mixture is generally in the range from 0.1 to 100 nCcm
−2
, preferably from 3 to 60 nCcm
−2
, particularly preferably from 5 to 40 nCcm
−2.
Compounds which are suitable for the preparation of a chip-card display mixture according to the invention can be described, for example, by the general formula (I)
R
1
(—A
1
—M
1
)
a
(—A
2
—M
2
)
b
—A
3
—(M
4
—A
4
)
c
—(M
5
—A
5
)
d
—R
2
  (I)
where the symbols and indices are defined as follows:
R
1
is
a) hydrogen, —F, —Cl, —CF
3
, —OCF
3
or —CN,
b) a straight-chain or branched alkyl radical (with or without an asymmetrical carbon atom) having 1 to 20 carbon atoms, where
1) one or more non-adjacent and non-terminal —CH
2
— groups may be replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—or —Si(CH
3
)
2
—, and/or
2) one or more —CH
2
—groups may be replaced by —CH═CH—, —C≡C—, cyclopropane-1,2-diyl, 1,4-phenylene, 1,4-cyclo-hexylene or 1,3-cyclopentylene, and/or
3) one or more H atoms may be replaced by F, CN and/or Cl, and/or
4) the terminal —CH
3
group may be replaced by one of the following chiral groups (optically active or racemic):
R
3
, R
4
, R
5
, R
6
and R
7
are identical or different and are
a) hydrogen
b) a straight-chain or branched alkyl radical (with or without an asymmetrical carbon atom) having 1 to 16 carbon atoms, where
b1) one or more non-adjacent and non-terminal —CH
2
— groups may be replaced by —O—, and/or
2) one or two —CH
2
— groups may be replaced by —CH═CH—,
c) R
4
and R
5
together may alternatively be —(CH
2
)
4
— or —(CH
2
)
5
— if they are bonded to an oxirane, dioxolane, tetrahydrofuran, tetrahydropyran, butyrolactone or valerolactone system;
R
2
is a straight-chain or branched alkyl radical (with or without an asymmetrical carbon atom) having 1 to 20 carbon atoms, where
a)one or more non-adjacent and non-terminal —CH
2
— groups may be replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O— or —Si(CH
3
)
2
—, and/or
b) one or more —CH
2
— groups may be replaced by —CH═CH—, —C≡—C—, cyclopropane-1,2-diyl, 1,4-phenylene, 1,4-cyclohexylene or 1,3-cyclopentylene;
M
1
, M
2
, M
4
and M
5
are identical or different and are a single bond or —CO—O—, —CO—S—, —CS—O—, —CS—S—, —CH
2
—O—, —CH
2
—S—, —CH
2
—CH
2
—, —CH═CH—, —C≡C—, —CH
2
—CH
2
—CO—O—, —CH
2
CH
2
CH
2
O—, —CH
2
CH
2
CH
2
CH
2
—, (E)—CH═CHCH
2
O—, and their mirror-image arrangements; or a single bond,
A
1
and A
5
are identical or different and are cyclohexane-1,4-diyl, 1-cyanocyclohexane-1,4-diyl, 1,3-dioxane-2,5-diyl, 5-cyano-1,3-dioxane-2,5-diyl, 1,3-dioxaborinane-2,5-diyl or 1-alkyl-1-silacyclohexane-1,4-diyl;
A
2
and A
4
are identical or different and are cyclohexane-1,4-diyl, 1-cyanocyclohexane-1,4-diyl, 1,3-dioxane-2,5-diyl, 5-cyano-1,3-dioxane-2,5-diyl, 1,3-dioxaborinane-2,5-diyl or 1-alkyl-1-silacyclohexane-1,4-diyl, 1,4-phenylene, 2-fluoro-1,4-phenylene, 2,3-difluoro-1,4-phenylene, pyrimidine-2,5-diyl, pyridine-2,5-diyl or 2-fluoropyridine-3,6-diyl;
A
3
is 1,4-phenylene, in which one or more H atoms may be replaced by F, Cl, CH
3
, C
2
H
5
, OCH
3
, CF
3
, OCF
3
and/or CN, pyrazine-2,5-diyl, in which one or two H atoms may be replaced by F, Cl and/or CN, pyridazine-3,6-diyl, in which one or two H atoms may be replaced by F, Cl and/or CN, pyridine-2,5-diyl, in which one or more H atoms may be replaced by F, Cl and/or CN, pyrimidine-2,5-diyl, in which one or two H atoms may be replaced by F, Cl and/or CN, 1,3,4-thiadiazole-2,5-diyl,

Affiliated with

Also associated with

Rating

Chip card with a bistable display does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Chip card with a bistable display, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Chip card with a bistable display will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2850369