Polymeric material for liquid crystal/polymer composite film, record display medium, and use thereof

A record display medium is provided which can offer a high display contrast and is less likely to cause a lowering of contrast or disappearance of display even in low temperature and high temperature regions. A polymeric material for a liquid crystal/polymer composite film comprising a liquid crystal present in a polymer matrix, a liquid crystal/polymer composite film using the material, and use of the record display medium are also provided. The polymeric material for a liquid crystal/polymer composite film comprising a liquid crystal present in a polymer matrix has a glass transition temperature of 150.degree. C. or above and is insoluble in water.

BACKGROUND OF THE INVENTION 
The present invention relates to a polymeric material useful for 
constructing a liquid crystal/polymer composite film, which is responsive 
to an electric field and heat and can display or record information, a 
liquid crystal/polymer composite film using the polymeric material, a 
record display medium using the composite film, and use of the record 
display medium. The record display medium can be widely used as rewritable 
cards, displays, and other record display media. 
Conventional liquid crystal display devices use a nematic liquid crystal as 
a liquid crystal and features including low power consumption, 
lightweight, and small thickness. By virtue of these features, they have 
been widely used as a display medium for letters and images in watches, 
electronic calculators, personal computers, televisions and the like. For 
general TN and STN liquid crystal display devices, a liquid crystal is 
filled into a liquid crystal cell comprising two glass plates, with a 
transparent electrode, and a predetermined seal provided between the two 
glass plate, and polarizing plates are put on respective both sides of the 
liquid crystal cell so that the liquid crystal cell is sandwiched between 
the polarizing plates. 
The above display devices have problems including that (1) necessity of 
using two polarizing plates results in small viewing angle and 
insufficient brightness results in unsatisfactory visibility, (2) the 
dependency upon the cell thickness is so large that it is difficult to 
realize a display having a large area, (3) a complicate structure of the 
device makes it difficult to fill a liquid crystal into the cell, posing 
problems such as high production cost and imposing a limitation regarding 
a reduction in weight, a reduction in thickness, an increase in area, a 
reduction in power consumption, a reduction in cost and the like on the 
display medium. 
The application of a liquid crystal/polymer composite film, comprising a 
liquid crystal present in a polymeric material as a matrix, to a record 
display medium is expected in order to solve the above problems, and 
research and development of the above composite film have become 
increasingly energetic. 
A large number of record display media using a liquid crystal/polymer 
composite film and processes for producing the same have been proposed in 
the art. One of them is a process for producing a record display medium 
from an emulsion of a liquid crystal dispersed in an aqueous polyvinyl 
alcohol (PVA) solution (Japanese Patent Publication No. 52843/1991). 
The record display medium prepared from an emulsion of a liquid crystal 
dispersed in an aqueous PVA solution is unsatisfactory in display 
characteristics such as contrast, drive voltage, and visibility. Further, 
since a water-soluble resin is used as the polymeric material for the 
matrix, the resultant medium has low moisture resistance. Furthermore, 
since the glass transition temperature (Tg) of the polymeric material is 
low, the resultant record display medium has a problem that when the 
temperature of the matrix of the record display medium becomes the glass 
transition temperature or above, micro motion of the polymer occurs, 
resulting in deteriorated display characteristics (contrast). 
Accordingly, an object of the present invention is to solve the above 
problems of the prior art and to provide a record display medium using a 
liquid/polymer composite, which record display medium has excellent 
contrast, visibility, moisture resistance, and heat resistance and can 
conduct displaying and recording of information such as in the form of a 
card or the like. 
DISCLOSURE OF INVENTION 
The above object can be attained by the present invention. Specifically, 
according to the present invention, there are provided a polymeric 
material, for a liquid crystal/polymer composite film comprising a liquid 
crystal present in a polymer matrix, wherein the polymeric material has a 
glass transition temperature or a decomposition temperature (if the glass 
transition temperature is absent) of 150.degree. C. or above and is 
soluble in an organic solvent and insoluble in water, a liquid 
crystal/polymer composite film using the material, a record display medium 
using the composite film, and use of the record display medium. 
Use of a particular polymer material as the matrix of the liquid 
crystal/polymer composite film comprising a liquid crystal present in a 
matrix can provide a record display medium which has excellent contrast, 
visibility, moisture resistance, and heat resistance and can conduct 
displaying and recording of information such as in the form of a card or 
the like.

BEST MODE FOR CARRYING OUT THE INVENTION 
The present invention will be described in more detail with reference to 
the following preferred embodiments. 
The polymeric material used as a matrix for immobilizing a liquid crystal 
according to one aspect of the present invention is a polymeric material 
for a liquid crystal/polymer composite film comprising a liquid crystal 
present in a polymer matrix, wherein it has a glass transition temperature 
or decomposition temperature of 150.degree. C. or above and is soluble in 
an organic solvent and insoluble in water. 
The polymeric material used as a matrix for immobilizing a liquid crystal 
according to another aspect of the present invention has a glass 
transition temperature or decomposition temperature of 150.degree. C. or 
above, substantially incompatible with the liquid crystal, causes phase 
separation from the liquid crystal, and is not substantially dyable with a 
dichroic dye. When the glass transition temperature or decomposition 
temperature is 150.degree. C. or above, the polymer causes no micro motion 
under usual service conditions, offering a stable record display medium. 
The polymeric material used as a matrix for immobilizing a liquid crystal 
according to a further aspect of the present invention is a polymeric 
material for a liquid crystal/polymer composite film comprising a liquid 
crystal present in a polymer matrix, wherein, when a value obtained by 
differentiating a display density value, for a constructed liquid 
crystal/polymer composite film, with respect to a storage temperature 
value is defined as a function, the function has a sharp peak, with the 
difference between the temperature, at which the maximum value is 
provided, and the phase transition temperature of the liquid crystal used 
being not more than 20.degree. C., the function having a half value width 
of not more than 10.degree. C. 
The polymeric material is incompatible with the liquid crystal and the 
dichroic dye and has excellent transparency and film-forming properties. 
Further, the polymeric material has excellent moisture resistance and heat 
stability and is less likely to be miscible with the liquid crystal, 
offering excellent long-term stability. Further, the polymeric material 
has a glass transition temperature or decomposition temperature of 
150.degree. C. or above and is rigid. When the glass transition 
temperature or decomposition temperature is 150.degree. C. or above, 
viscoelastic relaxation of a polymer chain segment based on micro-Brown 
motion is small. That is, in the polymeric material, the main dispersion 
is small. Even when the micro-Brown motion at the glass transition 
temperature or below is in a frozen state, one or two mechanical 
dispersions (secondary dispersions) occur. Use of a polymeric material 
having small mechanical dispersions as the matrix material is also 
important. The use of such a polymeric material results in improved heat 
resistance of the record display medium. Further, when a water-insoluble 
resin is used, moisture absorption and dissolution of the polymeric 
material as the matrix does not occur, resulting in improved moisture 
resistance of the record display medium. 
Specific examples of the above polymeric material include those comprising 
repeating units represented by the following general formula (1): 
##STR1## 
wherein R.sup.2 and R.sup.4 represent a hydrogen atom, a methyl group, or 
--(CH.sub.2).sub.n --COOR.sup.5 ; R.sup.3 represents a hydrogen atom or a 
methyl group, provided that R.sup.2 and R.sup.4 are not simultaneously a 
hydrogen atom; R.sup.1 and R.sup.5 may be the same or different and 
represent a hydrocarbon radical which may have a hetero atom and/or a 
substituent; and n is an integer of 0 to 5. 
Derivatives of itaconic acid wherein R.sup.2 =CH.sup.2 COOR.sup.5 and 
R.sup.3 =R.sup.4 =H may be mentioned as one example of monomers 
constituting repeating units in the polymeric material, and specific 
examples of preferred derivatives of itaconic acid include: diesters of 
itaconic acid containing a branched alkyl group with 3 to 12 carbon atoms 
or a substituted alkyl group, with 2 to 6 carbon atoms, containing a 
substituent of a cyclic structure having 3 to 14 carbon atoms, such as 
diisopropyl itaconate, di-t-butyl itaconate, dicyclohexyl itaconate, 
di-sec-butyl itaconate, di-4-methyl-2-pentyl itaconate, isopropyl-t-butyl 
itaconate, isopropyl-isoamyl itaconate, isopropyl-4-methyl-2-pentyl 
itaconate, isopropyl-2-ethylhexyl itaconate, isopropyl-nonyl itaconate, 
t-butyl-sec-butyl itaconate, t-butyl-isoamyl itaconate, 
t-butyl-4-methyl-2-pentyl itaconate, and t-butyl-2-ethylhexyl itaconate; 
diesters of itaconic acid having a siloxane hydrocarbon radical, such as 
methyl(trimethylsilyl) itaconate, ethyl(trimethylsilyl) itaconate, 
isopropyl(trimethylsilyl) itaconate, cyclohexyl(trimethylsilyl) itaconate, 
t-butyl(trimethylsilyl) itaconate, 
isopropyl(3-tris(trimethylsiloxy)silyl)propyl itaconate, and 
isopropyl-3-(pentamethyl)disiloxanyl)propyl itaconate; diesters of 
itaconic acid containing a hetero atom, such as 
N,N-dimethylaminoethyl-isopropyl itaconate, t-butyl-1-butoxy-2-propyl 
itaconate, 2-cyanoethyl-isopropyl itaconate, glycidyl isopropyl itaconate, 
diethylphosphonomethyl-isopropyl itaconate, and 
2-methylthioethyl-isopropyl itaconate; diesters of itaconic acid 
substituted by a halogen atom, such as perfluorooctylethyl-isopropyl 
itaconate, trifluoromethyl-isopropyl itaconate, pentafluoroethyl-isopropyl 
itaconate, hexafluoroisopropyl-isopropyl itaconate, and 
bis-1-chloroisopropyl itaconate. 
Derivatives of crotonic acid wherein R.sup.2 =R.sup.3 =H and R.sup.4 
=CH.sub.3 may be mentioned as another example of monomers constituting 
repeating units in the general formula (1), and specific examples of 
preferred derivatives of crotonic acid include: esters of crotonic acid 
containing a branched alkyl or cycloalkyl group with 3 to 12 carbon atoms 
or a substituted alkyl group, with 2 to 6 carbon atoms, containing a 
substituent of a cyclic structure having 3 to 14 carbon atoms, such as 
isopropyl crotonate, t-butyl crotonate, cyclohexyl crotonate, sec-butyl 
crotonate, 4-methyl-2-pentyl crotonate, isoamyl crotonate, 2-ethylhexyl 
crotonate, and nonyl crotonate; esters of crotonic acid having a siloxane 
hydrocarbon radical, such as trimethylsilylcrotonate, 
3-tris-(trimethylsiloxy)silylpropyl crotonate, and 
3-((pentamethyl)disiloxanyl)propyl crotonate; esters of crotonic acid 
containing a hetero atom, such as N,N-dimethylaminoethyl crotonate, 
1-butoxy-2-isopropyl crotonate, 2-cyanoethyl crotonate, glycidyl 
crotonate, diethylphosphonomethyl crotonate, and 2-methylthioethyl 
crotonate; esters of crotonic acid substituted by a halogen atom, such as 
perfluorooctylethyl crotonate, trifluoromethyl crotonate, pentafluoroethyl 
crotonate, hexafluoroisopropyl crotonate, and 1-chloroisopropyl crotonate. 
Derivatives of metaconic acid wherein R.sup.2 =H, R.sup.3 =CH.sub.3 and 
R.sup.4 =COOR.sup.5 may be mentioned as a further example of monomers 
constituting repeating units in the general formula (1), and specific 
examples of preferred derivatives of metaconic acid include: esters of 
metaconic acid having a hydrocarbon radical, such as dimethyl metaconate, 
diethyl metaconate, diisopropyl metaconate, dibutyl metaconate, di-t-butyl 
metaconate, dipentyl metaconate, dihexyl metaconate, diheptyl metaconate, 
dioctyl metaconate, di-2-ethylhexyl metaconate, dinonyl metaconate, 
didecyl metaconate, diundecyl metaconate, didodecyl metaconate, ditridecyl 
metaconate, diisotridecyl metaconate, dicyclohexyl metaconate, 
di-4-methyl-2-pentyl metaconate, isopropyl-t-butyl metaconate, 
isopropyl-isoamyl metaconate, isopropyl-4-methyl-2-pentyl metaconate, 
isopropyl-2-ethylhexyl metaconate, isopropyl-nonyl metaconate, 
t-butyl-sec-butyl metaconate, t-butyl-isoamyl metaconate, 
t-butyl-4-methyl-2-pentyl metaconate, t-butyl-2-ethylhexyl metaconate, 
diphenyl metaconate, and ditoluyl metaconate; diesters of metaconic acid 
having a silicon atom, such as methyl-(trimethylsilyl) metaconate, 
ethyl-(trimethylsilyl) metaconate, isopropyl-(trimethylsilyl) metaconate, 
cyclohexyl-(trimethylsilyl) metaconate, t-butyl-(trimethylsilyl) 
metaconate, isopropyl-(3-tris(trimethylsiloxy)silyl)propyl metaconate, and 
isopropyl-3-((pentamethyl)disiloxanyl)propyl metaconate; hetero 
atom-substituted diesters of metaconic acid, such as 
N,N-dimethylaminoethyl-isopropyl metaconate, t-butyl-1-butoxy-2-propyl 
metaconate, 2-cyanoethyl-isopropyl metaconate, glycidyl-isopropyl 
metaconate, diethylphosphomethyl-isopropyl metaconate, and 
2-methylthioethyl-isopropyl metaconate; diesters of metaconic acid having 
a halogen atom, such as perfluorooctylethyl-isopropyl metaconate, 
trifluoromethyl-isopropyl metaconate, pentafluoroethyl-isopropyl 
metaconate, hexafluoroisopropyl-isopropyl metaconate, and 
bis-1-chloroisopropyl metaconate. 
Specific examples of additional preferred monomers constituting repeating 
units in the general formula (1) include those comprising repeating units 
represented by the following general formula (2): 
##STR2## 
In the general formula (2), R.sup.1 and R.sup.6 may be the same or 
different and represent a hydrocarbon radical optionally having a hetero 
atom and/or a substituent, and specific examples thereof include alkyl, 
alkenyl, aryl, cycloalkyl, and cycloalkenyl groups. These groups may 
contain a silicon, nitrogen, oxygen, sulfur, or phosphorus atom as a 
hetero atom and a halogen atom or the like as a substituent. 
Specific examples of diesters of fumaric acid represented by the general 
formula (2) include: esters of fumaric acid having a hydrocarbon radical, 
such as dimethyl fumarate, diethyl fumarate, diisopropyl fumarate, dibutyl 
fumarate, di-t-butyl fumarate, dipentyl fumarate, dihexyl fumarate, 
diheptyl fumarate, dioctyl fumarate, di-2-ethylhexyl fumarate, dinonyl 
fumarate, didecyl fumarate, diundecyl fumarate, didodecyl fumarate, 
ditridecyl fumarate, diisotridecyl fumarate, dicyclohexyl fumarate, 
di-4-methyl-2-pentyl fumarate, isopropyl-t-butyl fumarate, 
isopropyl-isoamyl fumarate, isopropyl-4- methyl-2-pentyl fumarate, 
isopropyl-2-ethylhexyl fumarate, isopropyl-nonyl fumarate, 
t-butyl-sec-butyl fumarate, t-butyl-isoamyl fumarate, 
t-butyl-4-methyl-2-pentyl fumarate, t-butyl-2-ethylhexyl fumarate, 
diphenyl fumarate, and ditoluyl fumarate; diesters of fumaric acid having 
a silicon atom, such as methyl-(trimethylsilyl) fumarate, 
ethyl-(trimethylsilyl) fumarate, isopropyl-(trimethylsilyl) fumarate, 
cyclohexyl-(trimethylsilyl) fumarate, t-butyl-(trimethylsilyl) fumarate, 
isopropyl-(3-tris(trimethylsiloxy)silyl)propyl fumarate, and 
isopropyl-3-((pentamethyl)disiloxanyl)propyl fumarate; hetero 
atom-substituted diesters of fumaric acid, such as 
N,N-dimethylaminoethyl-isopropyl fumarate, t-butyl-1-butoxy-2-propyl 
fumarate, 2-cyanoethyl-isopropyl fumarate, glycidyl-isopropyl fumarate, 
diethylphosphomethyl-isopropyl fumarate, and 2-methylthioethyl-isopropyl 
fumarate; diesters of fumaric acid having a halogen atom, such as 
perfluorooctylethyl-isopropyl fumarate, trifluoromethyl-isopropyl 
fumarate, pentafluoroethyl-isopropyl fumarate, 
hexafluoroisopropyl-isopropyl fumarate, and bis-1-chloroisopropyl 
fumarate. 
Presence of repeating units represented by the general formula (1) or (2) 
suffices for the polymer comprising repeating units represented by the 
general formula (1) or (2). Further, the following additional repeating 
units may be incorporated by copolymerization at the time of the 
production of the polymer. 
Additional repeating units usable herein include half esters of fumaric 
acid of the types described above; polymerizable organic acids, such as 
(meth)acrylic acid, itaconic acid, citraconic acid, and maleic acid; 
esters of (meth)acrylic acid, such as methyl (meth)acrylate, ethyl 
(meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, hexyl 
(meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and 
cyclohexyl (meth)acrylate; nitrogen-containing acrylic compounds, such as 
amide (meth)acrylate, N,N-dimethylamide (meth)acrylate, and 
N,N-dimethylaminoethyl (meth)acrylate; vinyl ethers, such as methyl vinyl 
ether, ethyl vinyl ether, and isobutyl vinyl ether; vinyl esters, such as 
vinyl acetate and vinyl pivalate; allyl esters, such as allyl acetate and 
allyl benzoate; maleimides; and .alpha.-olefins, such as styrene, vinyl 
toluene, vinyl pyridine, vinyl chloride, vinylidene chloride, ethylene, 
and propylene. 
Polymeric materials usable as the matrix in the present invention may be 
used alone or as a mixture of two or more. The content of the repeating 
units represented by the general formula (1) or (2) in the polymeric 
material is not particularly limited. It is preferably not less than 50% 
by mole from the viewpoint of developing good display characteristics in 
the record display medium. Other thermoplastic resin(s) may be 
incorporated into the polymeric material according to the present 
invention. The incorporation of other resin(s) results in further improved 
adhesion of the substrate and the protective layer to the liquid 
crystal/polymer composite film. Preferred thermoplastic resins include a 
vinyl chloride/vinyl acetate copolymer, a polyester resin, a polyurethane 
resin, a polystyrene resin, and an acrylic resin. A plurality of 
thermoplastic resins may be incorporated into the polymer in order to 
further improve the adhesion. The amount of the above thermoplastic resin, 
if used, is 0 to 1,000 parts by weight, preferably 200 to 500 parts by 
weight, more preferably 300 to 400 parts by weight, based on 100 parts by 
weight of the polymeric material. 
The polymeric materials used in the matrix in the present invention may be 
produced by any conventional method without a particular limitation. For 
example, they may be prepared by polymerizing a monomer to be served as 
repeating units represented by the general formula (1) or (2) and, if 
necessary, other monomer(s) in the presence of a radical polymerization 
initiator at 0.degree. to 150.degree. C. for 1 to 100 hr. Polymerization 
initiators usable herein include benzoyl peroxide, diisopropyl 
peroxycarbonate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxypivalate, 
t-butyl peroxydiisobutyrate, lauroyl peroxide, and azobisisobutyronitrile. 
The polymeric materials comprising repeating units represented by the 
general formula (1) or (2) have a high glass transition temperature, and, 
in addition, when a very bulky substituent is introduced into the 
backbone, the secondary dispersion can be reduced. Further, despite the 
high glass transition temperature, the polymeric materials can be readily 
dissolved in a general-purpose solvent, such as toluene or methyl ethyl 
ketone, to prepare a homogeneous preparation, enabling the preparation of 
a homogeneous solution of the liquid crystal and the polymeric material. 
Furthermore, for the polymeric materials, since the carbon--carbon bond in 
the backbone cannot be easily rotated due to the presence of a bulky 
substituent bonded to the backbone, the polymeric materials are rigid. 
Therefore, they have low compatibility with the liquid crystal and is less 
likely to be dyed with a dichroic dye, enabling the preparation of record 
display media having a high contrast. 
The polymer matrix used in the record display medium according to the 
present invention comprises a polymer comprising repeating units 
represented by the following formula (A) and has an average molecular 
weight of 200,000 to 800,000: 
##STR3## 
An average molecular weight of less than 200,000 is unsatisfactory, e.g., 
because of low film strength of the liquid crystal/polymer film. An 
average molecular weight exceeding 800,000 is also unsatisfactory, e.g., 
because the solubility of the polymer matrix in the solvent is low, making 
it difficult to prepare a coating solution for the composite film. The 
average molecular weight is preferably in the range of from 300,000 to 
550,000. 
The above polymer may be a homopolymer consisting of repeating units 
represented by the formula (A). Alternatively, it may be a copolymer 
comprising the repeating units represented by the formula (A) and up to 
10% by mole, preferably 1 to 10% by mole of other copolymerizable 
monomer(s). Copolymerizable monomers usable herein include, for example, 
styrene, vinyl chloride, vinyl acetate, and acrylonitrile. Among them, 
styrene is preferred, e.g., because the resultant copolymer resin has a 
high glass transition temperature. 
The homopolymer or the copolymer may be used alone as the polymer. 
Alternatively, it may be used in the form of a polymer blend with up to 
10% by weight, preferably 1 to 10% by weight of other polymer(s). Other 
polymers which may be blended with the above polymer include, for example, 
polystyrene, polyvinyl chloride, polyvinyl acetate, polyester, and 
polyacrylonitrile. Among them, polystyrene is preferred, e.g., because the 
polymer blend has a high glass transition temperature. 
The above polymer matrix may be easily produced by a conventional 
polymerization method and, in addition, may be commercially available, for 
example, from Soken Chemical Engineering Co., Ltd. under the trade 
designation "PMMA M1002B." 
According to a preferred embodiment of the present invention, the polymer 
matrix contains at least one plasticizer in an amount up to 15% by weight, 
preferably in the range of from 0.01 to 15.0% by weight, based on the 
polymer matrix. Plasticizers usable herein include phthalic ester 
plasticizers, such as di-n-octyl phthalate, di-(2-ethylhexyl) phthalate, 
dinonyl phthalate, diisodecyl phthalate, and ditridecyl phthalate, and 
other conventional plasticizers, such as esters of dibasic esters, glycol 
esters, fatty esters, epoxy plasticizers and phosphoric esters. Use of 
these plasticizers results in enhanced processability of the polymer 
matrix and, at the same time, offers advantages such as increased 
flexibility, elasticity, and deflectability of the composite film. 
The polymeric material of the present invention, even when any liquid 
crystal (nematic, smectic, or cholesteric) is present therein, is less 
likely to be dyed with the liquid crystal or the dichroic dye and, hence, 
can offer a high contrast in the form of a record display medium. Examples 
of smectic liquid crystals which may be preferably used in the present 
invention include sodium myristate, sodium palmitate, sodium benzoate, 
ethyl p-azoxybenzoate, p-decyloxybenzylidene-p'-amino-2-methylbutyl 
cinnamate, p-hexyloxybenzylidene-p'-amino-2-chloropropyl cinnamate, and 
mixtures thereof. 
Liquid crystals which, when used with the polymeric material of the present 
invention, can offer high contrast and heat resistance include a smectic 
liquid crystal composition comprising: at least one member selected from 
compounds represented by the following general formula (I) 
##STR4## 
wherein R.sup.7 represents an alkyl or alkoxy group having 8 to 18 carbon 
atoms; and at least one member selected from compounds represented by the 
following general formulae (II) to (VII) 
##STR5## 
wherein R.sup.8, R.sup.10, R.sup.11, and R.sup.12 represent an alkyl group 
having 2 to 18 carbon atoms, R.sup.9, R .sup.13, R .sup.14, R.sup.15, and 
R.sup.16 represent an alkyl or alkoxy group having 2 to 18 carbon atoms, 
and X represents a halogen atom or an alkyl or alkoxy group having 2 to 18 
carbon atoms. 
Among these liquid crystals, 4-alkyl-4'-cyanobiphenyl or 
4-alkoxy-4'-cyanobiphenyl, having 8 to 18 carbon atoms, represented by the 
general formula (I) exhibits a stable smectic liquid crystal phase around 
room temperature and, in the form of a liquid crystal/polymer composite 
film type record display medium, provides a good contrast. Any one of 
these compounds may be used. In order to provide a stable smectic liquid 
crystal phase in a wider temperature range, at least two of these 
compounds may be properly selected and used in combination. 
4-Alkyl-4'-cyanobiphenyl or 4-alkoxy-4'-cyanobiphenyl compounds, having 7 
or less carbon atoms, when used alone, do not exhibit a smectic liquid 
crystal phase. However, the addition of the above compound having 8 to 18 
carbon atoms to these compounds enables adjustment to be made to a 
temperature region where a smectic liquid crystal phase is exhibited. 
Further, it can provide a more stable smectic liquid crystal phase. In 
this case, preferably, the 4-alkyl or 4-alkoxy-4'-cyanobiphenyl compound 
having 8 to 18 carbon atoms is added in an amount of at least 40% by 
weight to all the 4-alkyl or 4-alkoxy-4'-cyanobiphenyl compounds from the 
viewpoint of providing a stable smectic liquid crystal phase. 
The above compounds are known in the art (for example, Kusabayashi, 
"EKISHOU ZAIRYO," p. 229, published by Kodansha Ltd. (1991)), and, for 
example, 4-alkyl-4'-bromovinylphenyl or 4-alkoxy-4'-bromobiphenyl can be 
reacted with copper cyanide to give a corresponding 
4-alkyl-4'-cyanobiphenyl or 4-alkoxy-4'-cyanobiphenyl. Some of these 
compounds are commercially available. 
However, mere use of a compound, having a high smectic liquid crystal phase 
to nematic liquid crystal phase transition temperature or a smectic liquid 
crystal phase to isotropic phase transition temperature, as the compound 
represented by the general formula (I), gives rise to an increase in 
melting point and, when the record display medium is allowed to stand at a 
low temperature, causes the alignment of the liquid crystal to be 
disturbed, resulting in a lowering of contrast or disappearance of display 
in the record display area. 
For this reason, the present inventors have made studies with a view to 
increasing the phase transition temperature between the smectic liquid 
crystal phase and the nematic liquid crystal phase or between the smectic 
liquid crystal phase and the isotropic phase while keeping the melting 
temperature low and, as a result, have found that the addition of at least 
one of the compounds represented by the general formulae (II) to (VII) to 
the compound represented by the general formula (I) can realize this. 
The 4-alkylphenyl 4-alkoxybenzoate ester compounds or 4-alkoxyphenyl 
4-alkoxybenzoate ester compounds represented by the general formula (II) 
are known in the art (for example, Fluessige Kristalle in Tabellen, VED 
Deutscher Verlag fuer Grundstoffindustrie Leipzig, pp. 63-69, 1976) and 
can be prepared, for example, by esterifying a 4-alkylphenol with a 
4-alkoxy benzoate using a dicyclohexylcarbodiimide or the like as a 
dehydrating agent, and some of these compounds are commercially available. 
The 4-alkoxybiphenyl-4'-carboxylic acid alkyl ester compounds represented 
by the general formula (III) are known in the art for example, Mol. 
Cryst. Liq. Cryst., 37, pp. 157-188 (1976)! and can be simply prepared, 
for example, by esterifying an alkanol with a 
4-alkoxybiphenyl-4'-carboxylic acid in the presence of an acid catalyst 
such as sulfuric acid. 
The 4-alkyl-4"-cyano-p-terphenyl compounds represented by the general 
formula (IV) are known in the art for example, Mol. Cryst. Liq. Cryst., 
38, pp. 345-352 (1977)! and can be prepared, for example, by treating a 
4-alkyl-p-terphenyl-4"-carboxylic acid chloride with aqueous ammonia to 
give a 4-alkyl-p-terphenyl-4"-carboxylic acid amide which is then reacted 
with phosphorus pentoxide. Some of these compounds are commercially 
available. 
The 4'-cyanobiphenyl 4-alkylbenzoate ester or 4'-cyanobiphenyl 
4-alkoxybenzoate ester compounds represented by the general formula (V) 
are known in the art (for example, Fluessige Kristalle in Tabllen II, VED 
Deutscher Verlag fuer Grundstoffindustrie Leipzig, pp. 287-288, 1984) and 
can be prepared, for example, by esterifying a 4-alkylbenzoic acid or a 
4-alkoxybenzoic acid with 4-cyano-4'-hydroxybiphenyl using a 
dicyclohexylcarbodiimide or the like as a dehydrating agent. 
Among the compounds represented by the general formula (VI), most of the 
4-alkoxybiphenyl-4'-carboxylic acid 4-halophenyl ester compounds, 
4-alkoxybiphenyl-4'-carboxylic acid 4-alkylphenyl ester compounds, 
4-alkoxybiphenyl-4'-carboxylic acid 4-alkoxyphenyl ester compounds, 
4-alkylbiphenyl-4'-carboxylic acid 4-halophenyl ester compounds, 
4-alkylbiphenyl-4'-carboxylic acid 4-alkylphenyl ester compounds, and 
4-alkylbiphenyl-4'-carboxylic acid 4-alkoxyphenyl ester compounds are 
known in the art (for example, Fluessige Kristalle in Tabllen II, VED 
Deutscher Verlag fuer Grundstoffindustrie Leipzig, pp. 295-300, 1984) and 
can be prepared, for example, by esterifying a 
4-alkoxybiphenyl-4'-carboxylic acid or a 4-alkylbiphenyl-4'-carboxylic 
acid with a 4-halophenol or a 4-alkylphenol using a 
dicyclohexylcarbodiimide or the like as a dehydrating agent. The halogen 
element in these compounds may be of any kind. However, fluorine or 
chlorine is preferred from the viewpoint of chemical stability. 
The p-phenylene di-4-alkylbenzoate ester compounds, p-phenylene 
di-4-alkoxybenzoate ester compounds, and p-phenylene 4-alkylbenzoic 
acid-4-alkoxybenzoate ester compounds represented by the general formula 
(VII) are known in the art for example, J. Org. Chem., 37 (9), p. 1425 
(1972)! and can be prepared, for example, by reacting a p-alkylbenzoyl 
chloride or a p-alkoxybenzoyl chloride with hydroquinone under basic 
conditions and then reacting the reaction product with a p-alkylbenzoyl 
chloride or a p-alkoxybenzoyl chloride under basic conditions. 
The compounds represented by the general formulae (II) to (VII) serve to 
increase the smectic-nematic phase transition temperature or the 
smectic-isotropic phase transition temperature. The storage stability of 
records at high temperatures becomes better with increasing the phase 
transition temperature, and the phase transition temperature is preferably 
60.degree. C. or above, particularly preferably 60.degree. to 130.degree. 
C. 
However, when the phase transition temperature is excessively high, the 
state of alignment of liquid crystal molecules is less likely to be 
changed upon application of heat or an electric field. Therefore, a high 
phase transition temperature can enhance the storage stability of records 
in the record display medium in a high temperature region but requires 
high thermal energy or strong electric field for printing or erasing of 
information by application of heat or an electric field. For this reason, 
what is most important here is that records can be stored in the 
temperature range of from around -40.degree. to 100.degree. C., i.e., 
under usual service conditions of the record display medium. 
At least one compound or two or more compounds in combination which are 
properly selected from the above compound species so as to meet the above 
requirement may be used. Among the compounds represented by the general 
formulae (II) to (VII), those wherein the alkyl or alkoxyl group has 2 to 
18 carbon atoms are easily available. They have a phase transition 
temperature suitable for practical use and, in addition, are excellent in 
stability of the liquid crystalline phase. 
The compounds represented by the general formulae (II) to (VII) are 
incorporated in an amount of preferably 10 to 300 parts by weight, 
particularly preferably 20 to 240 parts by weight, based on 100 parts by 
weight of the compound represented by the general formula (I). 
Incorporation of 1 to 220 parts by weight, preferably 5 to 100 parts by 
weight, of at least one compound selected from the compounds represented 
by the general formulae (IV) to (VII) into 100 parts by weight of a 
mixture of the compound represented by the general formula (I) and the 
compound represented by the general formula (II) in a weight ratio of 
preferably 80:20 to 30:70, particularly preferably 60:40 to 40:60 is 
preferred because it can provide a liquid crystal composition which has a 
high contrast and causes neither a lowering of contrast nor disappearance 
of display in a high temperature region as well as in a considerably low 
temperature region, for example, at -40.degree. C. 
Other liquid crystalline compounds or additives may be added to the liquid 
crystal composition so far as they do not destroy the smectic liquid 
crystalline phase. In particular, the incorporation of a dichroic dye in 
an amount of 1 to 10 parts by weight based on 100 parts by weight of the 
liquid crystal composition is favorable for improving the contrast ratio 
or coloring or other purposes. 
According to a preferred embodiment of the present invention, a black 
dichroic dye comprising a mixture of azo dichroic dyes is added to the 
above liquid crystal compositions, particularly preferably the liquid 
crystal composition recited in claim 26, to improve the contrast ratio of 
a display image. The amount of the dichroic dye added may be, for example, 
1 to 10 parts by weight, preferably 1 to 3 parts by weight, based on 100 
parts by weight of the liquid crystal composition. 
Examples of dichroic dyes useful in the present invention are as follows. 
##STR6## 
All the above azo dichroic dyes are known in the art. In the present 
invention, two or more dichroic dyes are selected from the above azo 
dichroic dyes and mixed together to prepare a black mixture. Preferred is 
a mixture having a composition which, when used as the record display 
medium of the present invention, provides a difference in lightness 
between a written area and an erased area, .linevert 
split..DELTA.L*.linevert split., in the range of from 5 to 25 or a mixture 
having a composition which, when used as the record display medium of the 
present invention, provides a difference in chroma between a written area 
and an erased area, .linevert split..DELTA.C*.linevert split., in the 
range of from 0 to 10. 
The polymeric material and the liquid crystal composition can be used to 
form a liquid crystal/polymer composite film comprising a liquid crystal 
composition present in a matrix on a conductive substrate, thereby 
preparing the rewritable record display medium of the present invention. 
Specific preferred embodiments for the preparation of the liquid 
crystal/polymer composite film and the record display medium will be 
described. However, the present invention is not limited to these 
embodiments only. 
The amounts of the liquid crystal and the polymeric material used are not 
particularly limited. However, the mixing ratio (weight ratio) of the 
liquid crystal to the polymeric material is preferably 5:95 to 80:20, more 
preferably 35:65 to 45:55. When the amount of the liquid crystal used is 
excessively small, the transparency is unsatisfactory when an electric 
field is applied and, at the same time, a very high electric field is 
necessary for bringing the film to a transparent state. On the other hand, 
the use of an excessively large amount of the liquid crystal results in 
unsatisfactory scattering (turbidity) when heat is applied. Further, in 
this case, the strength of the film is deteriorated. 
The liquid crystal may be dispersed in the matrix comprising a polymeric 
material by any conventional method such as an emulsion or phase 
separation method with the phase separation method being useful. In the 
phase separation method, the polymeric material and the liquid crystal are 
dissolved in a common solvent, and the common solvent is evaporated from 
the mixed solution by solvent casting, development on a water surface or 
the like to form a film having a suitable thickness. According to the 
phase separation method, a liquid crystal/polymer composite film 
comprising a liquid crystal present in the formed film is formed. 
The formation of a liquid crystal/polymer composite film and a record 
display medium using a mixed solution containing the above smectic liquid 
crystal and the polymeric material can be carried out, for example, by 
coating the mixed solution on the surface of one conductive substrate for 
constructing the record display medium by suitable means, such as screen 
printing, stencil printing using a metallic mask, brush coating, spray 
coating, blade coating, doctor coating, or roll coating, drying the 
coating to form a liquid crystal/polymer composite film and optionally 
providing a protective layer to form the record display medium of the 
present invention. 
After the formation of the liquid crystal/polymer composite film on the 
conductive substrate by the above method, the other conductive substrate 
may be laminated onto the surface of the composite film. 
The conductive substrate used in the record display medium may be any 
conductive substrate commonly used in conventional liquid crystal display 
devices, and specific examples thereof include electrode substrates 
wherein a transparent conductive material, such as an ITO, SnO.sub.2 
-based, or ZnO-based material, is deposited onto a transparent substrate 
such as glass or a polymer film. In this case, when an opaque conductive 
substrate is used, a substrate with a reflective electrode of aluminum 
provided thereon is preferred because the opaque substrate is required to 
serve also as a reflector. The substrate per se may be made of glass, a 
polymer film or other material. A reflector of glass or a polymer film 
with Al.sub.2 O.sub.3, TiO.sub.2, ZnO or the like deposited thereon may be 
laminated onto the surface of the transparent conductive substrate remote 
from the liquid crystal/polymer composite film. 
In general, the thickness of the liquid crystal/polymer composite film 
provided between a pair of substrates or between the conductive substrate 
and the protective layer is preferably about 3 to 23 .mu.m. When the film 
thickness is less than the above range, problems arise such as lowered 
display contrast. On the other hand, when the film thickness exceeds the 
above ranges, problems arise such as increased voltage (drive voltage). 
According to one preferred embodiment of the present invention, there is 
provided a record display medium comprising a liquid crystal/polymer 
composite film provided between a pair of conductive substrates with at 
least one of the substrates being transparent, the liquid crystal/polymer 
composite film comprising a liquid crystal composition present in a 
polymeric material. 
According to another preferred embodiment of the present invention, there 
is provided an information display medium comprising the above 
liquid/polymer composite film provided on a conductive substrate and a 
protective layer, provided on the liquid crystal/polymer composite film, 
optionally through an intermediate layer. 
The intermediate layer may be formed of the same resin as used in the 
polymeric material. Such an intermediate layer and a protective layer 
formed of a thermosetting resin, an ultraviolet-curing resin, or an 
electron beam-curing resin, for example, a polyene-thiol, a polymerizable 
acrylate polymer, having in its molecule a (meth)acryloyl group, such as 
urethane acrylate, epoxy acrylate, or silicone acrylate, or a known curing 
resin comprising a monofunctional or polyfunctional monomer such as methyl 
methacrylate, are provided to form a rewritable record display medium. 
This embodiment will be described by taking an information rewritable card 
as an example. 
In the case of an information rewritable card, only one electrode is used. 
The substrate for the electrode is particularly preferably a polymer film. 
A white polyethylene terephthalate (PET) film is desired. A metal, such as 
aluminum, besides a transparent conductive material, such as ITO, may be 
used for the conductive layer. Further, a protective film is provided on 
the liquid/polymer composite film to protect the composite film. Although 
the material for the protective film is not particularly limited, a curing 
resin having mechanical strength, water resistance or other properties is 
preferred. 
For example, UV- or electron beam-curing poly(meth)acrylate or polyurethane 
(meth)acrylate is used. When the above protective film cannot be formed 
directly on the liquid crystal/polymer composite film, a thin film of a 
water-soluble polymer, such as polyvinyl alcohol, may be formed as an 
intermediate layer between the composite film and the protective film. 
Alternatively, the above protective film material formed on a separate 
sheet may be transferred or laminated and then cured to form a protective 
layer. 
In the case of an information rewritable card, the suitable range of the 
ratio of the liquid crystal to the polymer is different from that in the 
case of the display, and the weight ratio of the liquid crystal to the 
polymer is preferably 20:80 to 55:45. Further, the incorporation of a 
dichroic dye into the liquid crystal is preferred from the viewpoint of 
increasing the contrast of display. 
For the record display media (including cards) having the above 
constructions, recording and erasing of information will be described. 
In the record display medium using the liquid crystal/polymer composite 
film of the present invention, the application of an electric filed causes 
the liquid crystal to be aligned, rendering the liquid crystal/polymer 
composite film transparent. On the other hand, heating causes the 
alignment of the liquid crystal to be disturbed, bringing the liquid 
crystal/polymer composite film to the state of scatter and absorption. For 
example, writing of information may be performed by bringing the liquid 
crystal/polymer composite film to a transparent state, by applying an 
electric field, and then bringing the transparent film to the state of 
scatter and absorption by heating to write necessary information. In this 
case, the written information may be erased by applying an electric field 
to the whole area or heating the whole area. 
Conversely, writing of information may be performed by bringing the whole 
area of the liquid crystal/polymer composite film to the state of scatter 
and absorption and then applying an electric field to write necessary 
information. In this case, the written information may be erased by 
heating the whole area of the film or applying an electric filed to the 
whole area of the film. In particular, when writing and erasing are 
repeatedly conducted, it is preferred to use a method wherein information 
is written by applying one of an electric field or heat and erased by 
applying the remainder. Corona discharge is particularly useful for 
applying the electric field. In the case of the application of an electric 
field, satisfactory alignment of liquid crystal molecules in a short time 
can be expected by heating the liquid crystal/polymer composite film. 
Therefore, heating is preferably conducted according to need. 
The present invention will be described in more detail with reference to 
the following examples and comparative examples. 
Preparation of liquid crystal compositions 
Liquid crystal compounds listed in Table 1 were provided and mixed in 
various combinations as specified in Table 2 to prepare liquid crystal 
compositions. 
TABLE 1 
__________________________________________________________________________ 
Compounds of general formula (I) 
##STR7## 
##STR8## 
##STR9## 
##STR10## 
##STR11## 
##STR12## 
##STR13## 
##STR14## 
##STR15## 
Compounds of general formula (II) 
##STR16## 
##STR17## 
##STR18## 
##STR19## 
##STR20## 
##STR21## 
##STR22## 
##STR23## 
##STR24## 
##STR25## 
Compounds of general formula (III) 
##STR26## 
##STR27## 
Compounds of general formula (IV) 
##STR28## 
Compounds of general formula (V) 
##STR29## 
##STR30## 
Compounds of general formula (VI) 
##STR31## 
##STR32## 
##STR33## 
##STR34## 
Compounds of general formula (VII) 
##STR35## 
##STR36## 
__________________________________________________________________________ 
TABLE 2 
______________________________________ 
Composition A 
Composition B 
Composition C 
Composition D 
(wt %) (wt %) (wt %) (wt %) 
______________________________________ 
I-2 33.3 I-3 17.2 I-2 48.0 I-2 26.8 
I-7 16.7 I-5 17.2 I-7 24.0 I-7 13.2 
II-1 20.0 I-8 4.3 I-8 8.0 II-1 16.0 
II-2 30.0 I-9 3.8 IV-1 20.0 II-2 24.0 
II-1 17.0 V-1 20.0 
II-2 25.5 
III-2 15.0 
______________________________________ 
Composition E 
Composition F 
Composition G 
Composition H 
(wt %) (wt %) (wt %) (wt %) 
______________________________________ 
I-2 23.4 I-3 18.2 I-3 16.2 I-3 14.2 
I-7 11.6 I-5 18.2 I-5 16.2 I-5 14.2 
II-1 14.0 I-8 4.5 I-8 4.0 I-8 3.5 
II-2 21.0 I-9 4.1 I-9 3.6 I-9 3.1 
V-1 30.0 II-1 18.0 II-1 16.0 II-1 14.0 
II-2 27.0 II-2 24.0 II-2 21.0 
IV-1 10.0 V-1 20.0 IV-1 30.0 
______________________________________ 
Composition I 
Composition J 
Composition K 
Composition L 
(wt %) (wt %) (wt %) (wt %) 
______________________________________ 
I-1 23.5 I-1 23.5 I-3 18.2 I-3 18.2 
I-2 15.7 I-2 15.7 I-5 18.2 I-5 18.2 
I-6 16.8 I-6 16.8 I-8 4.5 I-8 4.5 
III-1 15.0 III-1 15.0 I-9 4.1 I-9 4.1 
III-2 4.0 III-2 4.0 II-1 18.0 II-1 18.0 
IV-1 25.0 V-1 15.0 II-2 27.0 II-2 27.0 
V-2 10.0 VI-1 10.0 VI-2 10.0 
______________________________________ 
Composition M 
Composition N 
Composition O 
Composition P 
(wt %) (wt %) (wt %) (wt %) 
______________________________________ 
I-3 17.2 I-5 17.2 I-5 18.2 I-5 20.3 
I-5 17.2 I-3 17.2 I-3 18.2 I-3 20.2 
I-8 4.3 I-9 3.8 I-9 4.1 I-9 4.5 
I-9 3.8 I-8 4.3 I-8 4.5 I-8 5.0 
II-1 17.0 II-1 17.0 II-1 18.0 II-3 12.5 
II-2 25.5 II-2 25.5 II-2 27.0 II-5 12.5 
VII-1 7.5 VI-4 15.0 VI-3 10.0 II-7 12.5 
VII-2 7.5 II-8 12.5 
______________________________________ 
Composition Q 
Composition R 
Composition S 
Composition T 
(wt %) (wt %) (wt %) (wt %) 
______________________________________ 
I-5 17.4 I-5 16.2 I-5 12.2 I-5 12.2 
I-3 17.4 I-3 16.2 I-3 12.1 I-3 12.1 
I-9 3.9 I-9 3.6 I-9 2.7 I-9 2.7 
I-8 4.3 I-8 4.0 I-8 3.0 I-8 3.0 
II-3 14.0 II-3 5.0 II-3 10.0 II-3 5.0 
II-6 14.0 II-4 5.0 II-6 15.0 II-4 5.0 
II-10 14.0 II-6 10.0 II-10 30.0 II-6 5.0 
IV-1 15.0 II-9 5.0 IV-1 15.0 II-8 5.0 
II-10 15.0 II-10 25.0 
IV-1 20.0 IV-1 25.0 
______________________________________ 
Composition U 
(wt %) 
______________________________________ 
I-3 12.1 
I-5 12.2 
I-8 3.0 
I-9 2.7 
II-3 5.0 
II-4 5.0 
II-6 5.0 
II-8 5.0 
II-10 20.0 
IV-1 30.0 
______________________________________ 
Measurement of Properties 
The above compositions were poured into a cell, which has a thickness of 12 
.mu.m, is provided with an aligning film of the polyimide, and has been 
subjected to parallel rubbing treatment, and the phase transition was 
observed under a polarizing microscope to measure the phase transition 
temperature at the time of temperature falling (-2.degree. C./min). The 
results are given in Table 3. In Table 3, I represents an isotropic 
liquid, S.sub.A a smectic A phase, S.sub.c a smectic C phase, S.sub.x a 
smectic X phase (the X phase being a smectic phase which cannot be 
identified as a general phase, such as S.sub.A or S.sub.c), N a nematic 
phase, and C a crystal. Further, -20.dwnarw. represents that the phase 
transition temperature is -20.degree. C. or below. 
EXAMPLE 1 
0.02 part by weight of a dichroic dye (S-428, manufactured by Mitsui Toatsu 
Chemicals, Inc.) was added to 1 part by weight of each of the smectic 
liquid crystal compositions A to U prepared above. 1 part by weight of 
polydiisopropyl fumarate (molecular weight 265,000, decomposition 
temperature 253.4.degree. C.) was added to each of the mixed solutions, 
followed by dissolution in 8 parts by weight of toluene. The decomposition 
temperature was measured by thermogravimetric analysis (TGA), and the 
molecular weight was determined by gel chromatography using a standard 
polyester (the same shall apply hereinafter). 
For comparison, 0.04 part by weight of a dichroic dye (S-428, manufactured 
by Mitsui Toatsu Chemicals, Inc.) was added to 2 parts by weight of a 
liquid crystal composition (S-6, manufactured by Merck), and 8.16 parts by 
weight of a 10 wt % aqueous solution of PVA (EG-05, manufactured by Nippon 
Synthetic Chemical Industry Co., Ltd.; degree of polymerization 500; 
degree of saponification 86.5 to 89.0) was added to the mixed solution, 
followed by mechanical dispersion. 
12.24 g of a 10 wt % aqueous solution of PVA (KH-20, manufactured by Nippon 
Synthetic Chemical Industry Co., Ltd.; degree of polymerization 2000; 
degree of saponification 78.5 to 81.5) was added as a thickening agent to 
the dispersion, and the mixture was stirred. 
These mixed solutions and dispersions were each coated on an ITO-deposited 
white polyethylene terephthalate substrate by means of a doctor blade, and 
the coatings were dried to form liquid crystal/polymer composite films. 
Subsequently, an ultraviolet curable resin (urethane acrylate) was coated 
on the whole surface of composite film by means of a doctor blade, and the 
resultant coatings were cured by irradiation with ultraviolet light from a 
high-pressure mercury lamp (output: 120 W/cm.sup.2) to form protective 
layers. Thus, record display media according to the present invention were 
prepared. 
For record display media using the liquid crystal/polymer composite films 
thus prepared, corona discharge (corona voltage: 6.5 kV) gave rise to an 
erased state, while thermal recording by means of a thermal head or the 
like gave rise to writing. 
The reflection density of the written area of the record display media in 
the above written state and the reflection density of the erased area were 
measured at room temperature with a color densitometer (RD 914-S, 
manufactured by Macbeth), the record display media were stored in a 
thermostatic chamber at 60.degree. C. and -40.degree. C. for 90 hr. The 
reflection density of the erased state was then measured, and the 
percentage change of reflection density in the erased state was calculated 
by the following equation. The results are given as the storage stability 
in Table 3. 
##EQU1## 
Further, the reflection density in the erased state was determined by 
taking the reflection density in the written state as 1.00, and the 
reflection density in the erased state was subtracted from the reflection 
density in the written state to determine the contrast. The results are 
also summarized in Table 3. 
As is apparent from the results, the record display media of the present 
invention are superior to the comparative record display medium in 
high-temperature storage stability, low-temperature storage stability, 
moisture resistance, and contrast. 
TABLE 3 
__________________________________________________________________________ 
Storage 
Storage 
Storage 
stability at 
Phase transition 
stability 
stability 
30.degree. C. and 
Composition 
temp. (.degree.C.) 
at 60.degree. C. 
at -40.degree. C. 
90% RH 
Contrast 
__________________________________________________________________________ 
A I(71)S.sub.A (-20.dwnarw.)C 
91 6 7 0.37 
B I(72)S.sub.A (-20.dwnarw.)C 
70 19 36 0.29 
C I(91)N(80)S.sub.A 
56 40 19 0.39 
(-11))S.sub.c (-17)C 
D I(86)N(81)S.sub.A 
17 5 6 0.46 
(-20.dwnarw.)C 
E I(101)N(89)S.sub.A 
E (-20.dwnarw.)C 
10 5 3 0.52 
F I(82)S.sub.A (-20.dwnarw.)C 
1 5 6 0.43 
G I(97)N(94)S.sub.A 
(-19)C 2 2 5 0.42 
H I(113)N(100)S.sub.A 
(10)C 5 13 7 0.43 
I I(94)N(79)S.sub.A 
(77)S.sub.A (-20.dwnarw.)C 
69 34 10 0.39 
J I(88)N(74)S.sub.A 
(19)S.sub.A (-20.dwnarw.)C 
9 12 6 0.45 
K I(85)S.sub.A (-20.dwnarw.)C 
47 5 4 0.46 
L I(85)S.sub.A (-20.dwnarw.)C 
3 3 4 0.46 
M I(83)S.sub.A (-20.dwnarw.)C 
8 7 5 0.45 
N I(88)S.sub.A (-16)C 
2 2 2 0.38 
O I(84)S.sub.A (-20.dwnarw.)C 
1 2 1 0.36 
P I(85)S.sub.A (-12)C 
4 9 1 0.38 
Q I(98)S.sub.A (-18)C 
4 1 3 0.43 
R I(110)S.sub.A (-17)C 
3 1 2 0.45 
S I(111)S.sub.A (-20.dwnarw.)C 
7 -3 5 0.39 
T I(117)S.sub.A (-20.dwnarw.)C 
0 -3 1 0.41 
U I(124)S.sub.A (-20.dwnarw.)C 
3 -10 1 0.40 
Comp. Ex. 
I(59)S 100 70 67 0.40 
__________________________________________________________________________ 
EXAMPLE 2 
A record display medium was prepared in the same manner as in Example 1, 
except that the smectic liquid crystal composition H and polydiisopropyl 
fumarate were used. The record display medium thus prepared was subjected 
to corona discharge (corona voltage: 6.5 kV) to bring the medium to an 
erased state. It was then stored at various temperatures to determine the 
percentage change of reflection density. The results are shown in FIG. 1. 
Further, data which have been differentiated with respect to the 
temperature are also shown in FIG. 1. 
The temperature of the phase transition from the smectic phase to the 
nematic phase for the smectic liquid crystal composition H used in this 
case was 100.degree. C., and, as can be judged from the differentiated 
data for the data on the percentage change of reflection density, the 
temperature at which the percentage change of reflection density was 
maximum was 95.degree. C. This maximum value shows the heat resistance of 
the record display medium. 
A smaller difference between the smectic to nematic phase transition 
temperature of the liquid crystal and the temperature at which the change 
of reflection density of the record display medium using the liquid 
crystal/polymer composite film is maximum means that the properties of the 
liquid crystal per se are better exhibited. Use of polymeric materials, 
which can satisfactorily bring out the properties of the liquid crystal, 
is important for record display media using liquid crystal/polymer 
composite film. The polymeric material of the present invention can 
satisfactorily utilize the properties of the liquid crystal. 
Thus, the use of the polymeric material of the present invention enables 
the heat resistance of the record display medium using the liquid 
crystal/polymer composite film to be suppressed to 20.degree. C. or below 
of the phase transition temperature of the liquid crystal used, permitting 
the ability of the liquid crystal used to be satisfactorily brought out. 
For the differentiated data shown in FIG. 1, the half value width is about 
8.degree. C. The smaller the half value width, the sharper the percentage 
change of reflection density as a function of the storage temperature. In 
the case of a display medium having a large half value width, the contrast 
unfavorably changes with the temperature even though the temperature at 
which the change of reflection density is maximum is high. The display 
medium, which causes a gradual change, and the polymeric material used for 
such a display medium are unsuitable. The temperature, at which the change 
of reflection density is maximum, and the half value width depend upon the 
polymeric material. Therefore, the selection of the polymeric material is 
important. 
EXAMPLE 3 
The record display medium of the present invention was prepared in the same 
manner as in Example 2, except that the smectic liquid crystal composition 
T was used instead of the smectic liquid crystal composition H in Example 
2. This record display medium was subjected to corona discharge (corona 
voltage: 6.5 kV) to bring the medium to an erased state in the same manner 
as in Example 2. It was then stored at various temperatures to determine 
the percentage change of reflection density. The results are shown in FIG. 
2. Further, data which have been differentiated with respect to the 
temperature are also shown in FIG. 2. 
The temperature, at which the change of reflection density was maximum, was 
105.degree. C. with the half value width being about 8.degree. C. The 
smectic to isotropic phase transition temperature for the smectic liquid 
crystal composition T was 117.degree. C. Thus, the polymeric material of 
the present invention could satisfactorily bring out the properties of the 
liquid crystal used. 
COMATIEVE EXAMPLE 1 
A record display medium was prepared in the same manner as in Example 2, 
except that polymethyl methacrylate (PMMA) (M.W.:15,000, manufactured by 
Junsei Kagaku K.K., Japan) was used instead of polydiisopropyl fumarate as 
the polymeric material. This record display medium was subjected to corona 
discharge (corona voltage: 6.5 kV) to bring the medium to an erased state. 
It was then stored at various temperatures to determine the percentage 
change of reflection density. The results are shown in FIG. 3. Further, 
data which have been differentiated with respect to the temperature are 
also shown in FIG. 3. 
The temperature, at which the change of reflection density was maximum, was 
90.degree. C. with the half value width being as large as about 15.degree. 
C., indicating that the percentage change of reflection density did not 
change sharply. The temperature, at which the percentage change of 
reflection density began to change, was 75.degree. C., indicating that the 
heat resistance was inferior to that in Example 2 using the same liquid 
crystal composition. 
EXAMPLE 4 
0.02 part by weight of a dichroic dye (S-428, manufactured by Mitsui Toatsu 
Chemicals, Inc.) was added to 1 part by weight of the smectic liquid 
crystal composition H. 1 part by weight of polydiisopropyl fumarate 
(molecular weight 265,000, decomposition temperature 253.4.degree. C.) was 
added to the mixed solution, followed by dissolution in 8 parts by weight 
of toluene. 
For comparison, mixed solutions were prepared in the same manner as 
described just above, except that, instead of polydiisopropyl fumarate, 1 
part by weight of polymethyl methacrylate (manufactured by Junsei Kagaku) 
was used for one comparative mixed solution and 1 part by weight of 
polystyrene (manufactured by Junsei Kagaku K.K., M.W.:15,000) was used for 
another comparative mixed solution. 
The above three mixed solutions were each coated on an ITO-deposited white 
polyethylene terephthalate substrate by means of a doctor blade, and the 
coatings were dried to form liquid crystal/polymer composite films. 
Subsequently, an ultraviolet curable resin (urethane acrylate) was coated 
on the whole surface of composite film by means of a doctor blade, and the 
resultant coatings were cured by irradiation with ultraviolet light from a 
high-pressure mercury lamp (output: 120 W/cm.sup.2) to form protective 
layers. Thus, record display media of the present invention and 
comparative record display media were prepared. 
For the three record display media thus prepared, the reflection density of 
the area from which information had been erased by application of an 
electric field was measured with a color densitometer (RD 914-S, 
manufactured by Macbeth), and, further, the contrast was also measured. 
The results were as tabulated in Table 4. 
TABLE 4 
______________________________________ 
Polymeric material 
Contrast 
______________________________________ 
Polydiisopropyl fumarate 
0.42 
Polymethyl methacrylate 
0.33 
Polystyrene 0.31 
______________________________________ 
Example 4 demonstrates that the record display medium using polymethyl 
methacrylate as the polymeric material has low heat resistance and, in 
addition, low contrast. 
Thus, since the polymeric material of the present invention is not dyeable 
with a dichroic dye, recording media using the polymeric material of the 
present invention exhibit higher contrast than recording media using other 
matrix resins, indicating that the record display media using the 
polymeric material of the present invention have excellent visibility. 
EXAMPLE 5 
0.02 part by weight of a dichroic dye (S-428, manufactured by Mitsui Toatsu 
Chemicals, Inc.) was added to 1 part by weight of the smectic liquid 
crystal composition H. 1 part by weight of a diisopropyl fumarate/allyl 
acetate copolymer (comonomer molar ratio 75/25, molecular weight 83,000, 
decomposition temperature 274.4.degree. C.) was added to the mixed 
solution, followed by dissolution in 8 parts by weight of toluene. 
This mixed solution was coated on an ITO-deposited white polyethylene 
terephthalate film substrate by means of a doctor blade, and the coating 
was dried to form a dried film. Subsequently, an ultraviolet curable resin 
(urethane acrylate) was coated on the whole surface of composite film by 
means of a doctor blade, and the resultant coating was cured by 
irradiation with ultraviolet light from a high-pressure mercury lamp 
(output: 120 W/cm.sup.2) to form a protective layer, thereby preparing a 
record display medium of the present invention. 
For this record display medium, erasing of information was performed at a 
corona voltage of 6.5 kV, and recording was performed by means of a 
thermal head. As a result, the reflection density of the recording medium 
in its area from which information had been erased was 0.690, while the 
reflection density of the written area was 1.204. This rewritable record 
display medium was held at 60.degree. C. for 90 hr. As a result, the 
reflection density of the erased area was 0.734. That is, the percentage 
change of reflection density in the erased area was as small as 9%, 
indicating that high memory effect could be provided. The record display 
medium on which information had been recorded by means of the thermal head 
was stored under conditions of 30.degree. C. and 90% RH for 90 hr. As a 
result, the percentage change of reflection density was as low as 6%, 
indicating that high memory effect could be provided. 
EXAMPLE 6 
A record display medium of the present invention was prepared and evaluated 
in the same manner as in Example 4, except that a diisopropyl 
fumarate/vinyl acetate copolymer (comonomer molar ratio 75/25, molecular 
weight 276,000, decomposition temperature 267.5.degree. C.) was used. 
As a result, the reflection density of the recording medium in its area 
from which information had been erased was 0.698, while the reflection 
density of the written area was 1.290. This rewritable record display 
medium was held at 60.degree. C. for 90 hr. As a result, the reflection 
density of the erased area was 0.745. That is, the percentage change of 
reflection density in the erased area was as small as 8%, indicating that 
high memory effect could be provided. The record display medium on which 
information had been recorded by means of the thermal head was stored 
under conditions of 30.degree. C. and 90% RH for 90 hr. As a result, the 
percentage change of reflection density in the erased area was as low as 
6%, indicating that high memory effect could be provided. 
EXAMPLE 7 
A record display medium of the present invention was prepared and evaluated 
in the same manner as in Example 4, except that a diisopropyl 
fumarate/methyl methacrylate copolymer (comonomer molar ratio 75/25, 
molecular weight 124,000, decomposition temperature 268.7.degree. C.) was 
used. 
As a result, the reflection density of the recording medium in its area 
from which information had been erased was 0.642, while the reflection 
density of the written area was 1.056. This rewritable record display 
medium was held at 60.degree. C. for 90 hr, and the reflection density of 
the erased area was then measured and found to be 0.657. That is, the 
percentage change of reflection density in the erased area was as small as 
4%, indicating that high memory effect could be provided. The record 
display medium on which information had been recorded by means of the 
thermal head was stored under conditions of 30.degree. C. and 90% RH for 
90 hr. As a result, the percentage change of reflection density in the 
erased area was as low as 4%, indicating that high memory effect could be 
provided. 
EXAMPLE 8 
0.02 part by weight of a dichroic dye (S-428, manufactured by Mitsui Toatsu 
Chemicals, Inc.) was added to 1 part by weight of the smectic liquid 
crystal composition U. 0.38 part by weight of polydiisopropyl fumarate 
(molecular weight 265,000, decomposition temperature 253.4.degree. C.), 
0.51 part by weight of a vinyl chloride/vinyl acetate copolymer resin 
(Vinylight VAGH, manufactured by Union Carbide), and 0.61 part by weight 
of a polyester resin (Vylon #200, manufactured by Toyobo Co., Ltd.) were 
added to the mixed solution, followed by dissolution in a mixed solvent of 
3.7 parts by weight of toluene, 0.13 part by weight of methyl ethyl 
ketone, and 0.02 part by weight of ethyl acetate. 
This mixed solution was coated on an ITO-deposited white polyethylene 
terephthalate film substrate by means of a doctor blade, and the coating 
was dried to form a dried film. Subsequently, an ultraviolet curable resin 
(urethane acrylate) was coated on the whole surface of composite film by 
means of a doctor blade, and the resultant coating was cured by 
irradiation with ultraviolet light from a high-pressure mercury lamp 
(output: 120 W/cm.sup.2) to form a protective layer, thereby preparing a 
record display medium of the present invention. 
For this record display medium, erasing of information was performed at a 
corona voltage of 6.5 kV, and recording was performed by means of a 
thermal head. As a result, the reflection density of the recording medium 
in its area from which information had been erased was 0.492, while the 
reflection density of the written area was 0.910. This rewritable record 
display medium was held at 60.degree. C. for 90 hr. As a result, the 
reflection density of the erased area was 0.504. That is, the percentage 
change of reflection density in the erased area was as small as 3%, 
indicating that high memory effect could be provided. The record display 
medium on which information had been recorded by means of the thermal head 
was stored under conditions of 30.degree. C. and 90% RH for 90 hr. As a 
result, the percentage change of reflection density in the erased area was 
as low as 1%, indicating that high memory effect could be provided. 
EXAMPLE 9 
A record display medium of the present invention was prepared and evaluated 
in the same manner as in Example 7, except that the smectic liquid crystal 
composition H was used. 
As a result, the reflection density of the recording medium in its area 
from which information had been erased was 0.606, while the reflection 
density of the written area was 1.070. This rewritable record display 
medium was held at 60.degree. C. for 90 hr. As a result, the reflection 
density of the erased area was 0.622. That is, the percentage change of 
reflection density in the erased area was as small as 3%, indicating that 
high memory effect could be provided. The record display medium on which 
information had been recorded by means of the thermal head was stored 
under conditions of 30.degree. C. and 90% RH for 90 hr. As a result, the 
percentage change of reflection density in the erased area was as low as 
2%, indicating that high memory effect could be provided. 
EXAMPLE 10 
1 part by weight of a smectic liquid crystal composition (13686, 
manufactured by Merck), 0.02 part by weight of a dichroic dye (S-428, 
manufactured by Mitsui Toatsu Chemicals, Inc.), and 1 part by weight of 
polydiisopropyl fumarate (molecular weight 265,000, decomposition 
temperature 253.4.degree. C.) were dissolved in 4 parts by weight of 
toluene. 
This mixed solution was coated on an ITO-deposited white polyethylene 
terephthalate substrate film by means of a doctor blade to form a coating 
having an even thickness, and the coating was dried to form a smectic 
liquid crystal/polymer composite film (thickness: 10.0 .mu.m). The 
resultant laminate sheet was stamped into a card having a size of 85 
mm.times.54 mm to prepare a rewritable card. At this point the liquid 
crystal layer was in a colored, opaque state. 
The liquid crystal in this card was aligned by corona discharge to render 
the liquid crystal layer transparent (this state being called "initially 
erased state"), and printing was performed by means of a thermal head to 
display an image (this state being called "initially written state"). The 
reflection density was measured for each state. The card was then stored 
for 90 hr in a thermostatic chamber kept at 60.degree. C., and the 
reflection density of the area in erased state (reflection density in 
erased area after storage) was measured. The percentage change of 
reflection density was calculated from these reflection density values by 
the above equation. As a result, it was found that the percentage change 
was as low as 7%, indicating that high memory effect could be provided 
even at a high temperature. This demonstrates that the card has excellent 
heat resistance. 
A card was prepared and subjected to printing in the same manner as 
described just above and stored for 90 hr in a thermostatic chamber kept 
at 30.degree. C. and 90% RH, and the reflection density of the area in 
erased state (reflection density in erased area after storage) was 
measured. The percentage change of reflection density was calculated from 
these reflection density values. As a result, it was found that the 
percentage change was as low as 3%, indicating that high memory effect 
could be provided even under high humidity. This demonstrates that the 
card has excellent moisture resistance. 
EXAMPLE 11 
1 part by weight of a smectic liquid crystal composition (17215, 
manufactured by Merck), 0.02 part by weight of a dichroic dye (S-428, 
manufactured by Mitsui Toatsu Chemicals, Inc.), and 1 part by weight of a 
diisopropyl fumarate/vinyl acetate copolymer (comonomer molar ratio 75:25, 
molecular weight 276,000, decomposition temperature 267.5.degree. C.) were 
dissolved in 4 parts by weight of toluene. 
This mixed solution was coated on an ITO-deposited white polyethylene 
terephthalate substrate film by means of a doctor blade to form a coating 
having an even thickness, and the coating was dried to form a smectic 
liquid crystal/polymer composite film (thickness: 10.0 .mu.m). The 
resultant laminate sheet was stamped into a card having a size of 85 
mm.times.54 mm to prepare a rewritable card. 
The liquid crystal in this card was aligned by corona discharge to render 
the liquid crystal layer transparent, and printing was performed by means 
of a thermal head to display an image. The reflection density was measured 
for each state. The card was then stored for 90 hr in a thermostatic 
chamber kept at 60.degree. C., and the reflection density of the area in 
erased state was measured. The percentage change of reflection density was 
calculated from these reflection density values by the above equation. As 
a result, it was found that the percentage change was as low as 4%, 
indicating that high memory effect could be provided even at a high 
temperature. This demonstrates that the card has excellent heat 
resistance. 
A card was prepared and subjected to printing in the same manner as 
described just above and stored for 90 hr in a thermostatic chamber kept 
at 30.degree. C. and 90% RH, and the reflection density of the area in 
erased state was measured. The percentage change of reflection density was 
calculated from these reflection density values. As a result, it was found 
that the percentage change was as low as 6%, indicating that high memory 
effect could be provided even under high humidity. This demonstrates that 
the card has excellent moisture resistance. 
EXAMPLE 12 
A rewritable card was prepared in the same manner as in Example 2, except 
that a diisopropyl fumarate/methyl methacrylate copolymer (comonomer molar 
ratio 75:25, molecular weight 124,000, decomposition temperature 
268.7.degree. C.) was used instead of the diisopropyl fumarate/vinyl 
acetate copolymer in Example 2. 
The liquid crystal in this card was aligned by corona discharge to render 
the liquid crystal layer transparent, and printing was performed by means 
of a thermal head to display an image. The reflection density was measured 
for each state. The card was then stored for 90 hr in a thermostatic 
chamber kept at 60.degree. C., and the reflection density of the area in 
erased state was measured. The percentage change of reflection density was 
calculated from these reflection density values by the above equation. As 
a result, it was found that the percentage change was as low as 4%, 
indicating that high memory effect could be provided even at a high 
temperature. This demonstrates that the card has excellent heat 
resistance. 
A card was prepared and subjected to printing in the same manner as 
described just above and stored for 90 hr in a thermostatic chamber kept 
at 30.degree. C. and 90% RH, and the reflection density of the area in 
erased state was measured. The percentage change of reflection density was 
calculated from these reflection density values. As a result, it was found 
that the percentage change was as low as 6%, indicating that high memory 
effect could be provided even under high humidity. This demonstrates that 
the card has excellent moisture resistance. 
EXAMPLE 13 
A rewritable card was prepared in the same manner as in Example 2, except 
that a diisopropyl fumarate/allyl acetate copolymer (comonomer molar ratio 
75:25, molecular weight 83,000, decomposition temperature 274.4.degree. 
C.) was used instead of the diisopropyl fumarate/vinyl acetate copolymer 
in Example 2. 
EXAMPLE 14 
A rewritable card was prepared in the same manner as in Example 2, except 
that a diisopropyl fumarate/styrene copolymer (comonomer molar ratio 9:1) 
was used instead of the diisopropyl fumarate/vinyl acetate copolymer in 
Example 2. 
For both Examples 13 and 14, the results were substantially the same as 
those of Examples 10 to 12 and were superior to those for light modulation 
devices, prepared by using polyvinyl alcohol as the polymer matrix. 
EXAMPLE 15 
0.04 part by weight of a dichroic dye (G241+G206+G472 (weight ratio=4:4:3), 
manufactured by Nihon Kanko Shikiso was added to 2 parts by weight of the 
smectic liquid crystal composition H (Table 3). The liquid crystal 
composition containing the dichroic dye was added to 30 parts by weight of 
a solution of 2.7 parts by weight of polymethyl methacrylate (PMMA M1002B, 
manufactured by Soken Chemical Engineering Co., Ltd., average molecular 
weight 300,000 to 550,000) and 0.3 part by weight of a plasticizer in 27 
parts by weight of a solvent (toluene/methyl ethyl ketone/ethyl acetate), 
and the mixture was stirred for 10 hr at room temperature to prepare a 
solution. The solution was coated by means of a doctor blade onto an 
ITO-deposited white PET substrate, and the coating was dried to prepare 8 
.mu.m-thick liquid crystal/polymer composite film. 
Further, an ultraviolet light curable resin (urethane acrylate) was coated 
by means of a doctor blade onto the whole surface of the liquid 
crystal/polymer composite film. The coating was irradiated with 
ultraviolet light emitted from a higher pressure mercury lamp (output 120 
W/cm.sup.2) to cure the coating, thereby forming a 2 .mu.m-thick 
protective layer. Thus, a record display medium according to the present 
invention was prepared. 
COMATIVE EXAMPLE 2 
A comparative record display medium was prepared in the same manner as in 
Example 15, except that polymethyl methacrylate (PMMA BR-113, manufactured 
by Mitsubishi Rayon Co., Ltd., average molecular weight 30,000) was used 
instead of polymethyl methacrylate in Example 15. 
A peel test, using a cellophane tape, and a pencil scratch test were made 
on the record display media prepared in Example 15 and Comparative Example 
2. As a result, for the record display medium prepared in Example 15, the 
composite film was not peeled in the peel test, and the pencil hardness 
was HB to B. On the other hand, for the record display medium prepared in 
Comparative Example 2, the composite film was easily peeled in the peel 
test, and the pencil hardness was 3B. 
For both the record display media prepared in Example 15 and Comparative 
Example 2, an erased state could provided by corona discharge (corona 
voltage 6.5 kv), and a written state could be provided by thermal 
recording using a thermal head or the like. 
The lightness and the chroma for the written area and the erased area in 
the written state of the record display medium were measured with a 
spectrophotometric calorimeter (CM-1000R, manufactured by Minolta). The 
difference in lightness between the written area and the erased area was 
11.1, and the difference in chroma between the written area and the erased 
area was 2.2, indicating that the displayed image had a high contrast. 
Thus, the present example demonstrated that a combination of the polymer of 
the present invention with a liquid crystal and a dichroic dye can offer a 
particularly high difference in lightness and chroma between a written 
area and an erased area. 
As is apparent from the foregoing description, according to the present 
invention, the use of a particular polymeric material as a matrix in a 
record display medium using a liquid crystal/polymer composite film can 
solve problems involved in the record display media of the prior art, such 
as disappearance of display under high temperature and/or high humidity 
conditions and, at the same time, can provide various rewritable record 
display media having improved reliability and stability as a device.