JPH0273220A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To increase the contrast ratio at the time when a low voltage is applied and to increase time constant by adding a compd. which is specific in dielectric constant into a medium for dispersing a liquid crystal. CONSTITUTION:The title device 1 is constituted of electrodes 2a, 2b respectively formed with transparent electrodes 3a, 3b and the medium layer 4. The layer 4 is formed by dispersing the liquid crystal and the compd. (A) having >=15 dielectric constant into a high-molecular compd. (e.g. polymethyl methacrylate). Org. matter (e.g. paranitroaniline), inorg. compd. (e.g. titanium oxide) or inorg. salt (e.g. ammonium hydrogenphosphate) is preferably used as the component A. A nematic liquid crystal, smectic liquid crystal, etc., are usable for the liquid crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device that has a large time constant when voltage is turned on and when voltage is turned off.

The liquid crystal display device of the present invention can be used in various displays, optical shutters, control devices, etc., and can be particularly suitably used as a large screen liquid crystal display device.

[Prior art and its problems]

Conventionally, various proposals have been made regarding liquid crystal display devices in which liquid crystals are dispersed in a medium.

For example, (1) Japanese Patent Publication No. 61-501345 proposes a liquid crystal material in which liquid crystal is microencapsulated in a polymer matrix, and (2) Japanese Patent Publication No. 62-22
No. 31 proposes a photoresponsive thin film comprising an ultraviolet curing reaction product of triallyl isocyanurate and a polythiol such as pentaerythritol tetrakis (2-mercapto-propanoate).

However, in conventional liquid crystal display devices, since the dielectric constant of the matrix polymer is not sufficiently large, the electric field inside the liquid crystal microcapsule layer is small when voltage is applied, and sufficient contrast cannot be obtained when low voltage is applied.

Furthermore, when performing matrix driving in a conventional liquid crystal display device using an active matrix method, the time constant [defined as the product of the liquid crystal layer capacitance 1i (etc.) and the liquid crystal layer resistance (RLC)] is not sufficiently large. As a result, flickering may occur or the display may become dark, making it difficult to drive at a high duty ratio. The electrical equivalent circuit of the liquid crystal microcapsule layer is shown below.

[Means for solving problems]

As a result of various studies on liquid crystal display devices in which liquid crystals are dispersed in a medium, the inventors of the present invention have found a liquid crystal display device that solves the above-mentioned problems.

The present invention consists of two substrates on which transparent electrodes are disposed, and a medium layer in which liquid crystal is dispersed in the medium, and the medium layer is
Relating to a liquid crystal display device having a configuration in which transparent electrode surfaces are sandwiched between two substrates so as to face each other, and the liquid crystal display device is characterized in that a polymer compound containing a compound having an ET'xN ratio of 15 or more is used as a medium. .

Examples of compounds having a dielectric constant of 15 or more to be contained in the medium in the present invention include organic substances such as cyclohexanol, succinonitrile, p-nitroaniline, 0-nitroaniline, and methanol, titanium oxide, lead oxide, and tin oxide. Metal oxides; metal halides such as lead chloride; inorganic substances such as bismuth oxide-cadmium oxide-silicon dioxide glasses, lead oxide-silicon dioxide glasses; niobic acids such as barium titanate, lead titanate, and lithium niobate. Inorganic compounds such as ferroelectric materials such as salts, ammonium hydrogen phosphate.

Preferred examples include hydrogen phosphate salts such as potassium hydrogen phosphate; inorganic salts such as ethylenediamine hydrogen tartrate and potassium hydrogen tartrate. In order to increase the time constant and contrast ratio of the liquid crystal display device, the inorganic compound used in the present invention is preferably in the form of fine powder, and the average particle size thereof is 5 μm or less, particularly 1 μm or less. Things (
, these are used by being dispersed in a polymer compound.

If the dielectric constant of the compound contained in the medium in the present invention is too low, the time constant will be low and flickering will likely occur when a liquid crystal display device is driven by a scanning pulse signal.

The liquid crystal used in the present invention is not particularly limited, and suitable examples include nematic liquid crystal, smectic liquid crystal, and the like.

The polymer compound used as a medium in the present invention includes:
Not limited in particular, polystyrene, polyvinyl chloride, polyvinyl alcohol, polycarbonate, butadiene rubber, polymethyl methacrylate, polymethacrylate,
Suitable examples include polyvinylpyrrolidone, cyanoethylcellulose, polyvinylidene fluoride, NBR (tolyl rubber), polysulfide rubber (thiokol), and the like.

The ratio of the compound with a dielectric constant of 15 or more and the polymer compound contained in the medium is 1 to 5,000 parts by weight per 100 parts by weight of the polymer compound in the case of an inorganic compound, and 1 to 5,000 parts by weight per 100 parts by weight of the polymer compound, and is used in an amount of 1 to 1000 parts by weight per 100 parts by weight of the polymer compound.

The ratio of the liquid crystal to the total of the above-mentioned compound with a dielectric constant of 15 or more and the polymer compound is not particularly limited, but it is 5 to 900 parts by weight per 100 parts by weight of the total of the compound with a dielectric constant of 15 or more and the polymer compound. LCD is used.

The present invention will be explained below with reference to the drawings.

FIG. 1 is a longitudinal sectional view of one embodiment of the liquid crystal display device of the present invention, which is constructed as follows. That is, two substrates 2a are provided with transparent electrodes 3a and 3b made of a composite oxide of indium and tin.

2b and a medium layer 4 in which liquid crystal is dispersed in a polymer compound containing a compound having a dielectric constant of 15 or more, and the medium layer is sandwiched between the two substrates so that the transparent electrode surfaces face each other. The structure is as follows.

The liquid crystal display device of the present invention is manufactured, for example, by the following method.

A liquid crystal, a compound with a dielectric constant of 15 or more, and a polymer compound are mixed, and this mixture is applied to a substrate 2a (glass, P
It is coated on the transparent electrode surface of a substrate such as ET film to obtain a medium layer in which liquid crystal is dispersed. Next, a liquid crystal display device can be manufactured by laminating the substrates 2b provided with the transparent electrodes 3b so that the transparent electrode surfaces are in contact with the medium layer, and sandwiching the medium layer between the substrates 2a and 2b.

FIG. 2 is a longitudinal cross-sectional view of a multiplex driving liquid crystal display device obtained according to the present invention.

A transparent pixel electrode 7 and a signal electrode 6 are formed on the substrate 5 by a known method such as patterning, and a varistor film 8 that connects the picture electrodes is formed by a known method such as screen printing. FIG. 3 is a diagram showing their arrangement relationship. A medium layer 11 in which liquid crystal is dispersed in a polymer compound containing a compound having a dielectric constant of 15 or more is sandwiched between a substrate 10 on which a scanning electrode 9 is provided and a substrate 5 . FIG. 4 is a diagram showing scanning electrodes 9 arranged on the substrate IO.

All known varistors can be used to form the varistor film. A composite oxide of indium and tin is conveniently employed as the material for the transparent pixel electrode 7 and the scanning electrode 9.

The liquid crystal display devices shown in FIGS. 2 to 4 are manufactured by coating a mixture of liquid crystal, a compound with a dielectric constant of 15 or more, and a polymer compound on a substrate 5 according to the same method as the device shown in FIG. A medium layer 11 was formed thereon. Subsequently, the scanning electrode 9 formed on the surface of the substrate 10 is connected to the pixel electrode 7 on the substrate 5.
It can be manufactured by stacking the medium layer 11 so as to face each other and sandwiching the medium layer 11 therebetween.

The liquid crystal display devices shown in FIGS. 2 to 4 can be suitably used as display devices for large screens.

〔Example〕

Example 1 2 g of PMMA and paranitroaniline (dielectric constant = 56) 0
．． 2 g and 2 g of liquid crystal were dissolved in 20 ml of chloroform to obtain a homogeneous solution. This solution was applied to a glass substrate with a transparent electrode using a barcoder, and after drying, a substrate provided with a transparent electrode was bonded to face the transparent electrode to produce a liquid crystal display device.

The time constant of this device was measured and was 3701 Ilsec.
Met. The contrast ratio is 14. when 50V voltage is applied.
It was 5.

Example 2 A liquid crystal display device for multiplex driving was manufactured by the following method. A schematic cross-sectional view of the liquid crystal display device is shown in the second figure.
As shown in the figure.

ZnO powder was molded at a pressure of 50 to 500 kg/ciil and fired at 700 to 1300°C in an electric furnace.

The obtained pellets are crushed in a mortar and classified to have a particle size of 5 to 8μ.
A powder of m was obtained. In order to round the corners of the powder, it was fired again at 800 to 1300°C in an electric furnace.

BizO, C was added to 100 g of the obtained spherical ZnO powder.

10, ,Mn0t, 5b20. After adding about several grams of the above ingredients and thoroughly mixing them, the mixture was fired at 700 to 1300°C to obtain a varistor powder. Ten grams of this powder, several grams of glass powder, and several grams of binder were thoroughly mixed to obtain a paste. The paste was printed at intervals of 50 μm through a predetermined screen on a transparent electrode-equipped substrate 5 (glass, PET film, etc.) that had been patterned with predetermined pixel electrodes 7 and signal electrodes 6 using ITO or the like in advance according to a conventional method. . 300-500
A substrate 5 on which a varistor film 8 was provided was fabricated by heat treatment at .degree.

FIG. 3 is a partially enlarged schematic plan view of the substrate 5 viewed from the signal electrode surface side.

Next, 2 g of PMMA, 0.2 g of paranitroaniline, and 2 g of liquid crystal were dissolved in 20 d of chloroform to obtain a homogeneous solution. This solution was applied onto the substrate 5 on which the varistor film 8 was disposed using a 50 μm doctor blade. Next, a transparent electrode-equipped substrate 10 (glass, PET film, etc.) on which a predetermined scanning electrode 9 has been patterned using ITO or the like in advance is shown in FIG. ) and the substrate 5 on which the varistor film 8 was disposed were bonded together so as to match at a predetermined position, and then cooled to room temperature. The medium layer 11 between the two substrates became cloudy and opaque. After that, the area around the board was sealed with adhesive.

Signal electrode 6 of liquid crystal display device 1 manufactured by the above method
When a drive circuit was connected between the electrode and the scanning electrode 9 and multiplex driving was performed at ±100V (duty ratio 1/400), clear display with a contrast ratio of 14 or more was achieved. According to this method, a multiplex drive liquid crystal display device using a varistor film as a nonlinear element can be easily obtained.
Moreover, since it has stable characteristics with little variation in film thickness, it can be used as a display device for large screens. Furthermore, by printing and baking the varistor film only between the pixel electrodes and the scanning electrodes, rather than over the entire substrate as in the conventional case, a transmissive display, which was previously impossible, can be achieved. In the above description, the signal electrode 6 and the scanning electrode 9 have been specifically explained, but the signal electrode 6 may be driven as a scanning electrode, and the scanning electrode may be driven as a signal electrode.

Comparative Example 1 A liquid crystal display device was manufactured in the same manner as in Example 1 except that varanitroaniline was not used, and when the time constant was measured, it was as small as 83 m5ec, and flickering was observed when driven by a scanning pulse signal. . Further, the contrast ratio was 7.8 when 50V was applied.

Example 3 Particle size 0.0 in 40g of 10% polyvinyl alcohol solution
2-0.05 am TiQ, powder (dielectric constant: 11
4) 4g was added and well dispersed. To this was added 15 g of liquid crystal containing several percent of the dye, and the mixture was stirred under reduced pressure to form an emulsion.

This solution was applied to a glass substrate with a transparent electrode using a barcoder, and after drying, a substrate provided with a transparent electrode was bonded to face the transparent electrode to produce a liquid crystal display device.

When the time constant of this device was measured, it was 890 m5ec. The contrast ratio was 28 when 50V'R pressure was applied, and 25 when 30V was applied.

Example 4 A liquid crystal display device was manufactured in the same manner as in Example 3 except that 40 g of neutral titania sol (dielectric constant: 114) was added instead of T i Oz powder, and the time constant was measured to be 740 m5ec. The contrast ratio was 31 at 50V.

Example 5 3 g of polymethyl methacrylate, 4 g of PbO powder (dielectric constant: 35), and 1.5 g of liquid crystal were added to 30 g of chloroform and stirred and mixed while degassing under slightly reduced pressure.

A liquid crystal display device was manufactured in the same manner as in Example 4, and the time constant was measured to be 720 m5ec, and the contrast ratio was 24 at 50V.

Example 6 4 g of 1'i02 powder (dielectric constant = 114) having a particle size of 0.02 to 0.05 μm was added to 40 g of a 10% by weight aqueous solution of polyvinyl alcohol, and well dispersed. To this was added 15 g of liquid crystal containing several percent of the dye, and the mixture was stirred under reduced pressure to form an emulsion. The obtained emulsion was applied to a substrate 5 on which a varistor film 8 prepared in the same manner as in Example 2 was disposed.
Coating was performed using a 0 μm doctor blade. Then,
A transparent electrode-coated substrate 10 (glass, PET film, etc.) with predetermined scanning electrodes 9 patterned using ITO or the like in advance;
FIG. 4 shows a partially enlarged schematic plan view of the substrate IO as seen from the scanning electrode surface side) and the substrate 5 on which the varistor film 8 is disposed.
After bonding them together in a predetermined position, they were cooled to room temperature. The medium layer 11 between the two substrates becomes dark and cloudy;
It became unclear.

After that, the area around the board was sealed with adhesive.

Signal electrode 6 of liquid crystal display device 1 manufactured by the above method
When a drive circuit was connected between the electrode and the scanning electrode 9 and multiplex driving was performed at ±100V (duty ratio 1/400), a clear display with a contrast ratio of 30 or more was obtained.

Example 7 After further desalting polyvinyl alcohol, 10%
Add 1 g of ammonium hydrogen phosphate to 40 g of this solution (NH4-11□POa; dielectric constant = 58)
was added. Furthermore, 15 g of liquid crystal containing a dye was added and stirred.

This solution was applied to a glass substrate with a transparent electrode using a bar coater, and after drying, a substrate provided with a transparent electrode was bonded so as to face the transparent electrode to produce a liquid crystal display device.

When the time constant of this device was measured, it was 215 m5ec. The contrast ratio was 18 when a voltage of 50V was applied, and 15 when a voltage of 25V was applied.

Example 8 After further desalting polyvinyl alcohol, 10%
1 g of ammonium hydrogen phosphate (NH<-11zPOai dielectric constant: 58) was added to 40 g of this solution. Furthermore, 15 g of liquid crystal containing a dye was added and stirred.

This solution was applied onto the substrate 5 on which the varistor film 8 prepared by the same method as in Example 2 was disposed using a 50 μm doctor blade. Next, a transparent electrode-equipped substrate 1 with predetermined scanning electrodes 9 patterned in advance using ITO or the like is prepared.
0 (glass, PET film, etc.; FIG. 4 shows a schematic plan view of a partially enlarged view of the substrate 10 from the scanning electrode surface side) and the substrate 5 on which the varistor film 8 is disposed are aligned at a predetermined position. After bonding, it was cooled to room temperature. The media layer 11 between the two substrates became dark black and opaque. After that, the area around the board was sealed with adhesive.

Signal electrode 6 of liquid crystal display device 1 manufactured by the above method
When a drive circuit was connected between the electrode 9 and the scanning electrode 9, and multiplex driving was performed at ±100 square meters (duty ratio 1/400), a clear display with a contrast ratio of 20 or more was obtained.

Comparative Example 3 A liquid crystal display device was manufactured in the same manner as in Example 7 except that ammonium hydrogen phosphate was not used, and when the time constant was measured, it was as low as 83 m5ec, flickering was observed, and the contrast ratio was determined by applying a voltage of 50 V. Sometimes it was 4.

〔Effect of the invention〕

The liquid crystal display device of the present invention has a voltage of 0N when a low voltage is applied.
-High contrast ratio when OFF, time constant 200m
It is large at 5 ec or more, so when driving a liquid crystal display device with a scanning pulse signal, flickering may occur.
It is possible to provide a large-screen liquid crystal display device in which the display is less likely to become dark, driving can be performed at a high duty ratio.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a liquid crystal display device of the present invention. Second
3 is a longitudinal cross-sectional view of a multiplex drive liquid crystal display device of the present invention, FIG. FIG. 4 is a plan view showing scanning electrodes arranged on a substrate. 1: Liquid crystal display device, 2a, 2b, 5, 10: Substrate, 3a
, 3b: transparent electrode, 4, 11: medium layer, 6: signal electrode,
7: Pixel electrode, 8: Varistor film, 9: Scanning electrode Figure 1 Figure 2 Patent applicant Ube Industries, Ltd.

Claims (4)

[Claims] (1) Consisting of two substrates on which transparent electrodes were arranged and a medium layer in which liquid crystal was dispersed in the medium, the medium layer was sandwiched between the two substrates so that the transparent electrode surfaces faced each other. 1. A liquid crystal display device according to the above structure, wherein a polymer compound containing a compound having a dielectric constant of 15 or more is used as a medium. (2) The liquid crystal display device according to claim 1, wherein an organic substance having a dielectric constant of 15 or more is used as a compound contained in the medium. (3) The liquid crystal display device according to claim 1, wherein an inorganic compound having a dielectric constant of 15 or more is used as the compound contained in the medium. (4) The liquid crystal display device according to claim 1, wherein an inorganic salt having a dielectric constant of 15 or more is used as the compound contained in the medium.