JP2639583B2 - Ferroelectric polymer liquid crystal device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device using a ferroelectric polymer liquid crystal, and more particularly, to a ferroelectric high-performance liquid crystal device which prevents a decrease in contrast due to alignment deterioration accompanying driving. The present invention relates to a molecular liquid crystal element.

[Related Art] Conventionally, low-molecular liquid crystals are often used in liquid crystal elements used for memories, displays, and the like in order to meet demands such as high-speed response. However, in recent years, in view of the demand for large-screen displays and simplification of mounting of liquid crystal elements, a so-called polymer liquid crystal composition such as a mixed system of a polymer liquid crystal compound and a low molecular liquid crystal compound, or a polymer liquid crystal system. Studies of liquid crystal devices using GaN have been conducted.

It is considered that the use of such a polymer liquid crystal composition is effective in the following points.

The polymer liquid crystal composition can be formed into a film by application of a solution or the like, and a large area of the liquid crystal element can be realized. The difficulties such as the control of the gap between the cell substrates performed in the above are solved.

Some polymer liquid crystal compositions can be oriented by stretching or the like, and there is a possibility that an alignment film used in low molecular liquid crystals is not required.

When a liquid crystal element is used for a memory, a display, or the like, a light-absorbing dye is included to improve contrast. In the case of the polymer liquid crystal composition, the compatibility of the polymer with the dye can be utilized, so that the dyes such as the dye and the pigment can be uniformly dispersed.

While such effectiveness is found, there is a drawback that it is not suitable for moving images and rewriting at high speed due to low response speed.

One of the methods to solve the above drawbacks is to use ferroelectric polymer liquid crystals [NAPlat et al. “Polymer Bulletin”), 12 ,
299, (1984)]. Since the response speed of the ferroelectric polymer liquid crystal can be greatly improved as compared with the conventional polymer liquid crystal, its practical application is expected.

[Problems to be Solved by the Invention] However, in the conventional example using the above-described ferroelectric polymer liquid crystal, the orientation of the ferroelectric polymer liquid crystal is increased due to the electrostrictive effect of the ferroelectric polymer liquid crystal. And the contrast and the responsiveness are reduced.
In particular, when it is intended to apply to a lightweight and flexible display element using a plastic film for a substrate, a solution has been desired.

The present invention has been made in order to improve such disadvantages of the prior art, and by using a plastic film having high tensile strength for a substrate and interposing a ferroelectric polymer liquid crystal between the film substrates. It is another object of the present invention to provide a ferroelectric polymer liquid crystal device in which the orientation of the ferroelectric polymer liquid crystal is prevented from deteriorating due to repeated driving, and the contrast is hardly reduced.

[Means for Solving the Problems] That is, the present invention relates to a ferroelectric polymer liquid crystal device in which a ferroelectric polymer liquid crystal is sandwiched between a pair of substrates having electrodes, wherein the substrate has a tensile strength of 200 kg / A ferroelectric polymer liquid crystal device characterized by being made of a plastic film having a size of ² cm or more.

 Hereinafter, the present invention will be described in detail.

FIG. 1A is a schematic view showing an example of the ferroelectric polymer liquid crystal device of the present invention, and FIG. 1B is a stripe provided on a pair of substrates of the ferroelectric polymer liquid crystal device of the present invention. FIG. 3 is a configuration diagram showing a relationship between a direction of a polar electrode and a polarization direction of a polarizing plate.
In the figure, a polarizing glass, or a plastic polarizing film such as one obtained by uniaxially stretching after adsorbing an iodine multimer on polyvinyl alcohol, or one uniaxially stretching after dyeing a dichroic dye on polyvinyl alcohol or polyethylene terephthalate. Between polarizing plates 4 and 4a, substrates 1, 1a
1 shows a liquid crystal element having a structure in which a laminated body having a ferroelectric polymer liquid crystal layer 2 interposed therebetween is provided. In FIG. 1 (a), the striped electrodes 3, 3a are provided outside the substrates 1, 1a.

FIG. 2 is a schematic view showing another example of the ferroelectric polymer liquid crystal device of the present invention, in which a stripe-shaped electrode 3, 3a is provided inside a substrate 1, 1a via an adhesive layer or an insulating layer. 1 shows a liquid crystal element having a structure. Alternatively, depending on the element configuration, a layered structure without an adhesive layer or an insulating layer may be used.

The substrate 1, 1a used in the present invention is a plastic film whose substrate material has a tensile strength of 200 kg / cm ² or more at ordinary room temperature, preferably 300 kg / cm ² or more, and a large area flexible liquid crystal. It is desirable in providing an element. If the tensile strength is less than 200 kg / cm ^2, by repeatedly subjected to stress generated by the electrostrictive effect at the time of the ferroelectric polymer liquid crystal elements are driven, gradually displaced to the substrate surface is generated, As a result, it affects the orientation of the ferroelectric polymer liquid crystal phase, and appears as orientation degradation.

As the substrate used in the present invention, a tensile strength of 200 kg / cm ² or more, it is preferable to use a polymer film in terms of providing a large area flexible element,
As specific examples, polyethylene terephthalate, polyester film such as polybutylene terephthalate,
Polycarbonate film, polyamide film, polyimide film, polymethyl methacrylate film, methyl methacrylate-styrene copolymer film, polystyrene film, polypropylene film, polyvinyl alcohol film, polyvinyl chloride film, polyvinylidene chloride film, polyvinylidene fluoride film, Examples include, but are not limited to, transparent films such as polyarylate films.

To use these films as the substrate,
Either an oriented film or a non-oriented film which has been subjected to a treatment such as uniaxial stretching or biaxial stretching can be used. The stretched film is one of the preferred treatments because it can improve the tensile strength to about 2 to 4 times (for example, in the case of polyethylene terephthalate).

The ferroelectric polymer liquid crystal used in the present invention includes a chiral smectic C phase (SmC ^* ) and an H phase (SmC ^* ).
H ^* ), I-phase (SmI ^* ), J-phase (SmJ ^* ), K-phase (SmK ^* ), G-phase (SmG ^* ) or F-phase (SmF ^* ) A chain type polymer liquid crystal compound or the like can be used, and specific examples thereof include the following, but are not limited thereto. (However, * in the formula indicates an asymmetric carbon center.) These ferroelectric polymer liquid crystals are used by mixing or copolymerizing one or two or more kinds, or by using a method suitable for device formation by a method such as being used by blending with a low-molecular liquid crystal compound. You.

Further, an optically active polymer liquid crystal that can exhibit ferroelectricity by blending can also be used. Specific examples are shown below. As a material to be blended, a general low-molecular ferroelectric liquid crystal is used. However, when blending with a low-molecular ferroelectric liquid crystal, compatibility must be considered. The ratio of the low-molecular liquid crystal to be blended is desirably in the range of 1 to 90%, preferably 5 to 50%.

In the present invention, after the ferroelectric polymer liquid crystal formed into a film is stretched, the ferroelectric polymer liquid crystal is press-bonded between substrates, or after the ferroelectric polymer liquid crystal and the substrate are laminated, they are shared with the substrate. An element having the structure shown in FIG. 1 or FIG. 2 can be obtained by a method such as stretching. These techniques are effective in providing orientation.

In addition, a conventionally known method can be used. For example, a method of heating and melting or dissolving in a solvent, coating the substrate, and then cooling or evaporating the solvent, respectively, may be mentioned.

In addition, the ferroelectric polymer liquid crystal layer formed on the substrate in this manner may be oriented by applying a shearing force at the time of coating, or the orientation treatment of an orientation film or the like may be performed on the substrate in advance and the isotropic phase may be applied. It is also possible to use a known alignment method such as gradually cooling to a liquid crystal phase.

[Function] The ferroelectric polymer liquid crystal device of the present invention is a ferroelectric polymer liquid crystal device in which a ferroelectric polymer liquid crystal is sandwiched between a pair of substrates having electrodes. the use of 200 kg / cm ² or more plastic film substrate, by receiving repeated stress ferroelectric polymeric liquid crystal element is generated by the electrostrictive effect at the time of being driven, to prevent changes occurring on the substrate surface As a result, the deterioration of the orientation of the ferroelectric polymer liquid crystal phase can be prevented, and the decrease in contrast can be extremely reduced.

[Example] Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1 Side chain type ferroelectric polymer liquid crystal represented by the following structural formula (I) Is dissolved in dichloroethane, and this is dissolved in a 40 μm-thick polyethylene terephthalate (PET) (tensile strength 700 kg / c
m ² ) Coating was performed on the substrate by spin coating, and dichloroethane was removed by heating to form a 3 μm thick liquid crystal film layer on the PET substrate. 40 on this LCD film layer
μm thick PET film is laminated and passed through a heat roll at about 85 ° C.
Uniaxial stretching was performed at a temperature indicating the C ^* phase to perform uniaxial orientation.

Next, as shown in FIG. 1 (b), a polyethylene terephthalate film with an ITO transparent electrode was adhered to the substrate vertically and vertically. Next, when sandwiched between two orthogonal polarizing plates, a voltage of ± 25 V, 20 Hz was applied, and the contrast of the transmitted light amount between the initial state and after driving for 24 hours was compared. Was.

When the polarizing plate of the device was removed and the alignment state was observed with a polarizing microscope, no disturbance in the alignment was observed.

Example 2 A ferroelectric polymer liquid crystal device of Example 1 was replaced with a laminate having the same frequency as that of Example 1 except that the substrate was changed to polyvinylidene chloride (tensile strength: 250 kg / cm ² ). Was applied, and the contrast of the amount of transmitted light at the initial stage and after 24 hours was compared. The contrast was 1: 4, 1: 3.8, and the reduction rate was 5%.

Observation of the orientation state with a polarizing microscope revealed that the disturbance of the uniaxial orientation was very slight.

Comparative Example 1 A laminate having the same frequency as that of Example 1 was obtained by using the ferroelectric polymer liquid crystal device of Example 1 except that the substrate was changed to low-density polyethylene (tensile strength: 130 kg / cm ² ). The contrast of the amount of transmitted light at the initial stage and after 24 hours was compared.
Fell by 1%.

Observation of the orientation state with a polarizing microscope revealed remarkable disorder of the orientation.

[Effects of the Invention] As described above, the ferroelectric polymer liquid crystal device of the present invention has a ferroelectric polymer liquid crystal sandwiched between substrates made of a plastic film having a tensile strength of 200 kg / cm ² or more. As a result, it is possible to prevent the deterioration of the orientation of the ferroelectric polymer liquid crystal due to the repeated driving, to reduce the contrast very little, and to provide an excellent effect that can be applied to a light-weight and large-area display element. .

[Brief description of the drawings]

FIG. 1A is a schematic view showing an example of the ferroelectric polymer liquid crystal device of the present invention, and FIG. 1B is a stripe provided on a pair of substrates of the ferroelectric polymer liquid crystal device of the present invention. Diagram showing the relationship between the direction of the plate-like electrode and the polarization direction of the polarizing plate, and FIG.
The figure is a schematic view showing another example of the ferroelectric polymer liquid crystal device of the present invention. 1, 1a ... substrate 2 ... ferroelectric polymer liquid crystal layer 3, 3a ... striped electrode 4, 4a ... polarizing plate 5, 5 '... arrow indicating polarization direction of polarizing plate

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yutaka Kurabayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takeo Eguchi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-63-318526 (JP, A)

Claims (1)

(57) [Claims] 1. A ferroelectric polymer liquid crystal device in which a ferroelectric polymer liquid crystal is sandwiched between a pair of substrates having electrodes, wherein the substrate is made of a plastic film having a tensile strength of 200 kg / cm ² or more. Characteristic ferroelectric polymer liquid crystal device.