Liquid crystal emulsion composition

A liquid crystal emulsion composition usable for forming a polymer dispersed type liquid crystal membrane free from undesirable bubbles, by a printing method, comprises 100 parts by weight of a liquid crystal material, 10 to 100 parts by weight of a saponification product of a polyvinyl acetate resin, 1 to 30 parts by weight of an aliphatic alcohol having 3 to 8 carbon atoms and 50 to 1,000 parts by weight of water.

BACKGROUND OF THE INVENTION 
1) Field of the Invention 
The present invention relates to a liquid crystal emulsion composition 
usable for providing a polymer dispersed type liquid crystal composite 
membrane through which a transmission of light can be controlled to a 
target value. 
2) Description of the Related Art 
Recently, a new type of liquid crystal composite membrane has been 
developed by utilizing a polymer dispersed type liquid crystal material, 
and this new type of liquid crystal composite membrane is useful as a 
film-shaped light shutter having a large area, or as a display means 
having a large area. 
Where a polymer dispersed type liquid crystal layer prepared from a liquid 
crystal material having a positive dielectric anisotropy and a polymeric 
matrix having a refractive index substantially equal to an ordinary 
refractive index of the liquid crystal material is interposed between a 
pair of electrode plates, the resultant liquid crystal device can scatter 
rays of light irradiated thereon when an electric field is not applied 
thereto, and can allow a transmission of the light therethrough when the 
electric field is applied thereto. 
Among various polymer dispersed types of liquid crystal materials, PCT 
International Publication No. WO 83/01016 discloses a Nematic Curvilinear 
Aligned Phase (NCAP) liquid crystal material; PCT Japanese Unexamined 
Patent Publication No. 60-252687 discloses a latex-entrapped liquid 
crystal material; PCT Japanese Publication No. 61-502128 discloses fine 
droplets of a liquid crystal material dispersed in an epoxy resin matrix, 
and Polymer Preprintings, Japan, Vol. 37, No. 8, 2450(1988) discloses a 
liquid crystal material composite membrane in which a liquid crystal 
material is formed into a network structure by a solvent casting method. 
The formation of the polymer dispersed type liquid crystal composite 
membrane on a surface of a base plate can be carried out by (1) coating a 
surface of a base plate with a liquid crystal emulsion with a doctor blade 
coater or roll coater, and then drying the resultant coated liquid crystal 
emulsion layer on the base plate, or (2) interposing a layer comprising a 
mixture of a liquid crystal material with a prepolymer, between a pair of 
base plates, and then curing the resultant interposed mixture layer by a 
heating or light-irradiation procedure. 
The above-mentioned methods are appropriate when forming a non-patterned 
polymer dispersed type liquid crystal composite membrane on a whole area 
of the base plate surface, but are disadvantageous in that, where a 
polymer dispersed type liquid crystal composite membrane must have a 
certain pattern, unnecessary portions of the non-patterned liquid crystal 
composite membrane must be removed in accordance with the required 
pattern. 
If a printing method can be applied, the patterned liquid crystal composite 
membrane will be easily formed in accordance with the required pattern, on 
the base plate surface, and the removal of the portions of the liquid 
crystal composite membrane, which is not economical, can be avoided. 
Nevertheless, when a conventional liquid crystal emulsion is printed in 
accordance with a required pattern, on a base plate surface, the resultant 
polymer dispersed type liquid crystal composite membrane is 
disadvantageous in that a number of bubbles are formed in the layer, and 
thus the smoothness of the resultant membrane surface is unsatisfactory. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a liquid crystal emulsion 
composition which is printable and useful for forming a polymer-dispersed 
type Iiquid crystal composite membrane in which no bubbles are formed. 
Another object of the present invention is to provide a liquid crystal 
emulsion composition useful for forming a polymer dispersed type liquid 
crystal composite membrane having an enhanced surface smoothness. 
The above-mentioned objects can be attained by the liquid crystal emulsion 
composition of the present invention, which comprises 100 parts by weight 
of a liquid crystal material; 10 to 100 parts by weight of a 
saponification product of a polyvinyl acetate resin; 1 to 30 parts by 
weight of at least one aliphatic alcohol having 3 to 8 carbon atoms; and 
50 to 1,000 parts by weight of water. 
The liquid crystal emulsion composition of the present invention optionally 
comprises 0.01 to 10 parts by weight of a pleochroic dye, per 100 parts by 
weight of the liquid crystal material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the liquid crystal emulsion composition, the liquid crystal material 
comprises at least one member selected from the group consisting of 
nematic liquid crystal materials, cholesteric liquid crystal material and 
smectic liquid crystal materials. 
The saponification product of the polyvinyl acetate resin usable for the 
present invention, referred to as polyvinyl alcohol hereinafter, is 
soluble in water and preferably has a degree of polymerization of 100 to 
10,000, more preferably 200 to 3000, and a degree of saponification of 50% 
to 100%, more preferably 60 to 90%. 
The polyvinyl alcohol resin is present in a content of 10 to 100 parts by 
weight per 100 parts by weight of the liquid crystal material, and the 
polyvinyl alcohol resin forms a transparent polymer matrix in which the 
liquid crystal material is dispersed. If the content of the polyvinyl 
alcohol in the emulsion composition is less than 10 parts, the resultant 
liquid crystal composite membrane exhibits an unsatisfactory stability. 
Also, if the content of the polyvinyl alcohol is more than 100 parts by 
weight, the resultant liquid crystal composite membrane exhibits an 
unsatisfactory contrast ratio. 
The polyvinyl alcohol resin can be dissolved in water or in an aqueous 
solution of an aliphatic alcohol having 3 to 8 carbon atoms. 
The aliphatic alcohol usable for the present invention has 3 to 8 carbon 
atoms, and is present in an amount of 1 to 30 parts by weight per 100 
parts by weight of the liquid crystal material. 
In the liquid crystal emulsion composition, a portion of the specific 
aliphatic alcohol is dissolved in the liquid crystal phase and the other 
portion of the aliphatic alcohol is dissolved together with the polyvinyl 
alcohol resin in a water phase. 
The specific aliphatic alcohol is advantageous in that the aliphatic 
alcohol accelerates the emulsification of the liquid crystal material in 
the polyvinyl alcohol aqueous solution; promotes the removal of bubbles or 
foam formed in the liquid crystal emulsion composition during the 
emulsifying operation; or introduced into the printed or coated liquid 
crystal emulsion composition layer during the printing, especially screen 
printing operation or coating operation. 
Further, the specific aliphatic alcohol effectively enhances the surface 
smoothness of the resultant liquid crystal composite membrane. 
If the content of the specific aliphatic alcohol is less than 1 part the 
resultant polymer dispersed type liquid crystal composite membrane 
contains bubbles or pores formed therein and/or has an unsatisfactory 
surface smoothness. 
If the specific aliphatic alcohol is employed in an amount of more than 30 
parts, it is difficult to smoothly coat or print the resultant liquid 
crystal emulsion on the base plate surface. 
The aliphatic alcohol is preferably selected from the group consisting of 
n-butyl alcohol, n-pentylalcohol, isobutyl alcohol, tert-butyl alcohol, 
isopropyl alcohol, hexyl alcohol, 2-butyl alcohol and isoamyl alcohol. 
If an aliphatic alcohol having 2 or less carbon atoms is employed, the 
resultant liquid crystal emulsion composition exhibits an unsatisfactory 
bubble-removing effect and emulsification-promoting effect. 
Also, if an aliphatic alcohol having 9 or more carbon atoms is used, the 
resultant liquid crystal emulsion composition exhibits an unsatisfactory 
bubble-removing effect and is difficult to be dried by evaporation. 
Among the above-mentioned aliphatic alcohols having 3 to 8 carbon atoms, 
n-butyl alcohol and n-pentyl alcohol are especially preferable for the 
present invention because, when a liquid crystal emulsion composition 
containing these aliphatic alcohols is printed and dried in accordance 
with a desired pattern on a base plate surface, the resultant dried 
polymer dispersed type liquid crystal composite membrane substantially 
does not contain the aliphatic alcohol, and even if a portion of the 
above-mentioned aliphatic alcohol remains, the resultant liquid crystal 
composite membrane is not adversely influenced by the remaining aliphatic 
alcohol. 
Also, the liquid crystal emulsion composition of the present invention can 
provide a specific polymer dispersed type liquid crystal composite 
membrane having a better voltage-luminance relationship than that of 
another polymer dispersed type liquid crystal composite membrane formed 
from a conventional liquid crystal emulsion composition. 
The liquid crystal emulsion composition of the present invention can be 
converted to a corresponding polymer dispersed type liquid crystal 
composite membrane by, for example, the following method. 
A liquid crystal material is mixed with predetermined amounts of the 
polyvinyl alcohol, the specific aliphatic alcohol, and water, at room 
temperature, to provide an emulsion composition. The resultant liquid 
crystal emulsion composition is coated by a coater, for example, doctor 
blade coater or roll coater, or printed by a screen printing method, on a 
base plate surface, and the resultant emulsion composition layer is dried 
to provide a polymer dispersed type liquid crystal composite membrane. 
Optionally, the liquid crystal emulsion composition of the present 
invention further comprises 0.01 to 10 parts by weight of a pleochroic dye 
selected from, for example, anthraquinone type or azo type pleochroic 
dyes, per 100 parts by weight of the liquid crystal material. 
The pleochroic dye added to the liquid crystal emulsion composition 
effectively enhances the contrast ratio. 
EXAMPLES 
The present invention will be further illustrated by means of the following 
examples. 
EXAMPLE 1 
A liquid crystal emulsion composition was prepared by stirring a mixture of 
10 g of a liquid crystal material available under the trademark of LIQUID 
CRYSTAL E-44 from Merck Japan Co. and containing 2% by weight of a 
pleochroic black dye available under the trademark of S-344 from Mitsui 
Toatsu Senryo K.K., 20 g of an aqueous solution containing 15% by weight 
of polyvinyl alcohol resin available under the trademark of GOSENOL KM-11, 
from Nihon Gosei Kagaku Kogyo K.K., and 3 g of n-butyl alcohol, at a 
rotation speed of 800 rpm for 8 minutes to emulsify the mixture. 
The resultant liquid crystal emulsion composition was printed through a 180 
mesh printing screen in accordance with a predetermined pattern on a glass 
base plate coated with ITO and the printed emulsion composition layer was 
dried to provide a polymer ispersed type liquid crystal composite membrane 
having a thickness of 15 .mu.m. This composite membrane was free from 
bubbles and pores and had a smooth surface. 
The liquid crystal composite membrane was interposed between a pair of ITO 
base plates and the side edges of the resultant laminate were sealed by an 
adhesive, to provide a display panel. 
The resultant panel was arranged at a location 20 cm from a light source 
(fluorescent lamp) of 15,000 nit and voltages of 30 to 100 volts were 
applied to the panel. The luminance of the panel (amount of light 
transmitted through the polymer dispersed liquid crystal material layer) 
was measured by a luminance meter. 
The results of the measurement are shown in Table 1. 
COMATIVE EXAMPLE 1 
The same procedures as in Example 1 were carried out except that, in the 
preparation of the liquid crystal emulsion composition, n-butyl alcohol 
was not added. 
It was found that, when the liquid crystal emulsion composition was printed 
on the ITO-coated glass base plate surface through the 180 mesh printing 
screen, a number of air bubbles were formed in the resultant liquid 
crystal emulsion composition layer. 
Accordingly, the liquid crystal emulsion composition was coated on the 
ITO-coated glass base plate by using a doctor blade coater, to provide a 
polymer-dispersed type liquid crystal composite membrane having a 
thickness of 15 .mu.m. 
This liquid crystal composite membrane was subjected to the provision of 
the same type of display panel as in Example 1, and the resultant panel 
was subjected to the same measurement of the voltage-luminance 
relationship as in Example 1. 
The results are shown in Table 1. 
TABLE 1 
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Item Luminance (nit) under voltage of: 
Example No. 
0 volt 30 volts 50 volts 
70 volts 
100 volts 
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Example 1 
41 52 520 2500 4160 
Comparative 
50 190 1090 1950 3080 
Example 1 
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Table 1 clearly shows that the light transmission through the liquid 
crystal composite membrane prepared from the liquid crystal emulsion 
composition of the present invention is significantly increased under a 
high voltage. 
Also it was confirmed that the liquid crystal emulsion composition of the 
present invention can form a polymer dispersed type liquid crystal 
composite membrane by a printing method, especially a screen printing 
method, without forming bubbles therein.