JP2578424B2 - Ferroelectric polymer liquid crystal device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquid crystal device using a ferroelectric polymer liquid crystal, and more particularly to a liquid crystal device capable of forming a thin film, comprising a substrate and a ferroelectric polymer liquid crystal layer. The present invention relates to a liquid crystal element having good adhesion.

[Conventional technology]

Conventionally, application of a polymer liquid crystal used for a high-strength, high-elasticity fiber or the like as a display element or a memory element has been studied similarly to a low-molecular liquid crystal. One of the problems when using a polymer liquid crystal as a liquid crystal element is the orientation direction of the polymer liquid crystal. In the case of polymer liquid crystals, the method of stretching and orienting the polymer liquid crystal using the stretch orientation of the polymer is characteristic. This method uses an alignment film to apply a force to the polymer liquid crystal itself. For example, higher orientation can be expected as compared with methods conventionally used for low-molecular liquid crystals.

In recent years, ferroelectric polymer liquid crystals have been studied to improve the responsiveness and contrast of liquid crystal devices.However, in order to realize a bistable state of liquid crystals, liquid crystals are used in the same way as low-molecular ferroelectric liquid crystals. It is necessary to make the thickness of the layer sufficiently thin.

The application of the stretch alignment technique to polymer liquid crystals is described in, for example,
61-137133 and JP-A-61-160847, all of which cannot realize the bistable state of the above-mentioned ferroelectric polymer liquid crystal because the liquid crystal layer thickness is large, and reduce contrast and responsiveness. Sufficient ones have not been obtained.

[Object of the invention]

Therefore, the present invention provides a ferroelectric polymer liquid crystal device having a favorable bistable state by stretching and thinning the ferroelectric polymer liquid crystal, and particularly, these devices provide a display device and a storage device. It is an object of the present invention to provide a ferroelectric polymer liquid crystal element which can be used well.

Another object of the present invention is to provide a liquid crystal device of the present invention, which can be used as a recording device, for example, as a ferroelectric material capable of satisfying high-speed response, high contrast, and storage stability. Provide a polymer liquid crystal device.

[Means and actions for achieving purpose]

Accordingly, the present invention provides a ferroelectric polymer liquid crystal device having a ferroelectric polymer liquid crystal layer stretched and oriented between a pair of substrates and having a layer thickness of 0.1 to 5 μm after the stretch orientation.

Specific examples of the ferroelectric polymer liquid crystal applied to the present invention include NAPlati, VP Shibaev Pure & Appl. Chem., 57, 15
89 (1985) as shown in equation (1),
It is not limited to this.

In addition, the ferroelectric polymer used in the present invention includes adjustment of glass transition temperature and Curie temperature, adjustment of spontaneous polarization and magnitude of anti-electric field, and the like. It may be used in combination with another polymer or a polymer liquid crystal in order to improve the mechanical characteristics in device fabrication.

Further, for example, the following dyes may be added to the recording medium.

In the present invention, after stretching the film-shaped ferroelectric polymer liquid crystal, it may be pressed between the substrates, but if only the ferroelectric polymer liquid crystal is stretched,
At the same time as the liquid crystal alignment is improved, a strong anisotropy is easily generated in the mechanical strength of the ferroelectric polymer liquid crystal itself, and the adhesion between the substrate and the liquid crystal layer is also likely to be reduced. Therefore, it is preferable that the ferroelectric polymer liquid crystal and the substrate are laminated and then co-stretched together with the substrate. By co-stretching, the substrate and the ferroelectric polymer liquid crystal are aligned in the same direction, and the substrate can be expected to function as an alignment layer. In addition, since the liquid crystal layer is held on the substrate even when the liquid crystal layer exhibits mechanical anisotropy due to stretching in addition to good adhesion between the substrate and the liquid crystal layer, the liquid crystal layer can be obtained as a stable thin film.

In the present invention, a ferroelectric polymer liquid crystal layer is laminated on a substrate, stretched, and then pressure-bonded to a second substrate to form a liquid crystal element, or further mechanical stability of the liquid crystal layer during stretching. For the sake of performance, a laminate in which a ferroelectric polymer liquid crystal exists between two substrates may be stretched.

The substrate that can be used for the liquid crystal element of the present invention must be a stretchable substrate such as plastic when the substrate is stretched and aligned, but if not stretched, any conventionally known substrate may be used. it can.

In the present invention, as a method of laminating a ferroelectric polymer liquid crystal on a substrate as a support, a conventionally used method can be used.

For example, a method in which a ferroelectric polymer liquid crystal is heated and melted to have a relatively fluid state such as a nematic phase or an isotropic liquid, and then applied to a substrate serving as a support may be considered. In this case, the coating method is to apply a high shearing property to the viscosity of the polymer liquid crystal melted by heating and the coating festival, and then to perform the orientation by stretching more efficiently. For example, blade coating, knife coating, Extrusion coating and the like are effective.

On the other hand, it is possible to laminate the polymer liquid crystal on the substrate by applying the ferroelectric polymer liquid crystal on a substrate in a state of being dissolved in an appropriate solvent and removing the solvent. In this case, the viscosity of the ferroelectric polymer liquid crystal solution can be changed depending on the concentration of the ferroelectric polymer liquid crystal in the solution. Although the number of the liquid crystal molecules increases, the alignment of the polymer liquid crystal after the removal of the solvent does not occur, so that the alignment must be performed only by the subsequent stretching, and there is also a disadvantage that the variation in the alignment by increasing the number of alignment processing means is reduced. . Coating method may be considered in each case, but in addition to the above-mentioned coating method on the substrate, ferroelectric polymer liquid crystal is heated and pressed on the substrate by compression molding or the like, or T-die extrusion is performed. It can also be laminated by laminating a ferroelectric polymer liquid crystal formed into a sheet or a film by a coextrusion method or the like with an appropriate substrate.

On the other hand, as a method of stretching a laminate composed of a substrate and a ferroelectric polymer liquid crystal, a method conventionally used for stretching and orienting a polymer can be applied.

That is, examples include uniaxial stretching (free width, constant width), sequential biaxial stretching, and simultaneous biaxial stretching. Of these stretching methods, the highest orientation of the polymer liquid crystal is uniaxial stretching, and it is preferable to perform uniaxial stretching.However, in order to improve the mechanical strength of the stretched film, for example, in sequential biaxial stretching,
Sequential biaxial stretching close to uniaxial stretching may be performed by extremely changing the biaxial stretching ratio.

In the present invention, the stretching ratio is more preferably set in the range of 10 to 1500%, and further preferably 20 to 500%. However, this stretching ratio is the ratio of the stretched length when the film is stretched to its original length and then brought into a stable state. In the case of biaxial stretching, the biaxial stretching ratio is preferably from 1: 1 to 1:50. As a specific method of stretching, for example, in the case of uniaxial stretching, a method of passing a laminate of a ferroelectric polymer liquid crystal and a substrate between two pairs of rotating rolls having different surface speeds can be mentioned.

The temperature of the ferroelectric polymer liquid crystal layer at the time of stretching can be performed at a temperature equal to or higher than the glass transition temperature and equal to or lower than the transition temperature to the isotropic liquid as in the case of the general polymer. , SmC ^* phase, and quenching immediately below the glass transition point immediately after stretching to fix the structure. Also by stretching
In order to make the SmC ^* phase monodomain, a method of applying an electric field in a direction perpendicular to the film surface at the time of stretching to uniformly align the direction of spontaneous polarization is also possible.

On the other hand, depending on the polymer liquid crystal, it may be better to perform so-called cold stretching in which stretching is performed at a temperature equal to or lower than the glass transition point from the viewpoint of high orientation.

The ferroelectric polymer liquid crystal device of the present invention can be used for a memory or a display by combining it with an electrode material such as a transparent electrode or a matrix electrode as in the conventional liquid crystal device. When using a ferroelectric polymer liquid crystal device, it is necessary to reduce the thickness of the liquid crystal layer to form a bistable state, as in the case of the conventional low-molecular ferroelectric liquid crystal device. Further, the light to be given to the liquid crystal element,
In order to improve the sensitivity to heat and an electric field, the liquid crystal layer is preferably in a thin film state. The thickness of the ferroelectric polymer liquid crystal layer after the stretching treatment is suitably from 0.1 μm to 5 μm from the necessity of reading the memory and the contrast for display.

FIG. 1 is a sectional view of one embodiment of the liquid crystal device of the present invention, and FIG. 3 is a sectional view of another embodiment. In the drawing, reference numeral 1 denotes a substrate, 2
Represents an electrode, 3 represents an adhesive layer, 4 and 4 'represent a substrate, 5 represents a ferroelectric polymer layer, 15 represents a striped electrode, and 16 represents a polarizing glass.

When the liquid crystal element of the present invention is used as an information recording medium such as an optical card or a display element, for example, the ferroelectric polymer liquid crystal layer oriented in a certain direction by stretching orientation is irradiated with a laser beam, or the liquid crystal layer is heated by a thermal head. Or by applying an electric field to change the orientation state of the ferroelectric polymer liquid crystal layer and the direction of spontaneous polarization. Information can be read or displayed by a difference in light transmittance or birefringence) or a difference in electrical characteristics (piezoelectricity or pyroelectricity) depending on the presence or absence of ferroelectricity.

The liquid crystal device of the present invention is a device having a ferroelectric polymer liquid crystal stretched and aligned between substrates. Since the thickness of the ferroelectric polymer liquid crystal layer is sufficiently small, the ferroelectric polymer liquid crystal has a favorable bilayer. A stable state can be formed, and the sensitivity of the ferroelectric polymer liquid crystal layer to photothermal and electric fields is improved. Is also big.

 Hereinafter, the present invention will be described more specifically with reference to Examples.

[Examples 1 to 3] (See FIG. 1) Side chain type ferroelectric polymer liquid crystal having polymethacrylate represented by the following structural formula as a main chain Dissolved in dichloroethane and represented by the following structural formula Was added at 0.1 wt%. This was coated on a 100 μm thick polyethylene terephthalate (PET) 4 substrate by spin coating to remove dichloroethane, thereby forming an 8 μm liquid crystal film layer 5 on the PET substrate. A 100 μm thick PET film 4 ′ is laminated on this liquid crystal film layer and passed through a heat roll at about 85 ° C. to obtain a laminate having a ferroelectric polymer liquid crystal layer between two PET film substrates. Was.

The obtained laminate was passed through a pair of rollers having different surface velocities under an environment in which the ferroelectric polymer liquid crystal exhibited an SmC ^* phase to perform uniaxial stretching with a free width.

The laminated body after stretching was rapidly cooled to a temperature lower than the glass transition point of the polymer liquid crystal, and the ferroelectric polymer liquid crystal layer was fixed with SmC ^* (ferroelectric phase).

Next, a laminated body having a ferroelectric polymer liquid crystal layer 5 obtained by evaporating an ITO film 2 on a polycarbonate substrate 1 having a thickness of 1.5 mm and having a pregroove with a stamper, and extending the ITO film 2 thereon. 6 was cut into a wallet size and bonded to produce an optical card having a configuration as shown in FIG.

Information was written on the obtained optical card by the recording device shown in FIG.

Semiconductor laser monitoring pre-groove (λ = 83
0nm) 12 light is irradiated on the optical card, and at the same time, the output is adjusted according to the film thickness to change the ferroelectric liquid crystal layer of the optical card from room temperature
Heat to the temperature indicated by C ^* . The needle electrode 7 is arranged at the center of the irradiation light of the semiconductor laser light, and a pulse voltage of ± 15 V is applied to the needle electrode 7 in accordance with the recorded information, thereby forming an electric field between the ITO film of the optical card and the needle electrode, thereby increasing the strength. Information was recorded by reversing the spontaneous polarization of the dielectric polymer liquid crystal layer.

The information recorded in the bistable state of the ferroelectric polymer liquid crystal layer is irradiated with the output of the semiconductor laser lowered to 0.1 mw without applying a voltage to the needle electrode, and the transmitted light attributed to the bistable state is irradiated. By detecting the difference in birefringence, reading could be performed with good reproduction contrast. This optical card can rewrite information even when information is already recorded by performing the same recording method as described above.

Table 1 shows the thickness, reproduction contrast, and recording responsiveness of the obtained polymer liquid crystal layer for three types of stretching ratios (100, 200, and 300%).

[Examples 4 to 6] A laminate 6 composed of PET and a ferroelectric polymer liquid crystal obtained in the same manner as in Example 1 except that no light-absorbing dye was added was uniaxially stretched in the same manner as in Example 1. 1.5m on both sides
Adhesion 1 and FIG. 3 (a) on a polarizing glass 16 having a thickness of m and a substrate provided with a stripe-shaped ITO film 15 in the same direction as the polarization direction so that the ITO films are orthogonal to each other (see FIG. 3 (b)). Thus, a liquid crystal element as shown in FIG. The obtained laminate is placed on a transparent resistance heating element stage 21 having a backlight light source 20, the ferroelectric polymer liquid crystal layer is heated to SmC ^*, and a voltage is applied between the matrix-structured ITO films. A display having a configuration as shown in FIG. 4 was obtained. The voltage applied to the ITO film was 10 V. Table 2 shows the contrast and response of the display.

[Examples 7, 8] The procedures were performed in the same manner as in Examples 1 to 3 and Examples 4 to 6 except that uniaxial stretching was performed at a stretching ratio of 5%. The results are shown in Tables 1 and 2 as Examples 7 and 8, respectively.

[Comparative Examples 1 and 2] Comparative examples 1 and 2 were performed in the same manner as in Examples 1 to 3 and Examples 4 to 6 except that uniaxial stretching was not performed in Examples 1 to 3 and Examples 4 to 6, respectively. 2 are shown in Tables 1 and 2.

[Explanation of Effect] The present invention is a ferroelectric liquid crystal device having a ferroelectric polymer liquid crystal stretched and aligned between a pair of substrates, and a thin film state (thickness) in which the ferroelectric polymer liquid crystal layer is easily aligned. 0.1 ~ 5μ
m), the ferroelectric polymer liquid crystal exhibits a good bistable state because it can be obtained in (m). Therefore, when this liquid crystal element is used for a recording or display element, the reproduction or display contrast ratio is good and the responsiveness of recording and display is high. And storage stability can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view of an optical card according to the first embodiment of the present invention, FIG. 2 is a schematic diagram of a recording / reproducing apparatus for the optical card according to the first embodiment of the present invention, and FIG. FIG. 3 (b) is a cross-sectional view of the device, and FIG. 3 (b) is a configuration showing the relationship between the direction of the stripe-shaped electrodes provided on the polarizing glass substrate and the polarization direction and the laminating direction of the two polarizing glass substrates of Example 2 of the present invention FIG. 4 is a schematic diagram of a display device according to Embodiment 2 of the present invention. 1 is a substrate, 2 is an electrode, 3 is an adhesive layer, 4,4 'is a substrate, 5 is a ferroelectric polymer liquid crystal layer, 6 is a laminate of 4, 4' and 5 layers, 7
Is a needle electrode, 8 is a pulse voltage generator, 9 is an optical card, 10
Is a moving stage, 11 is a light intensity detector, 12 is a semiconductor laser, 13 is a polarizer, 14 is an analyzer, 15 is a striped electrode,
16 is a polarizing glass, 17 and 17 ′ are arrows indicating the polarizing direction of the polarizing glass, 18 is a voltage generator, 19 is a power supply for a resistance heating element, 20
Is a backlight, 21 is a transparent stage, 22 is a display element, 23
Indicates a transparent resistance heating element.

 ──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-63-72784 (JP, A) JP-A-63-109419 (JP, A) JP-A-62-227122 (JP, A) JP-A-61-227 160847 (JP, A) JP-A-61-137133 (JP, A)

Claims (12)

(57) [Claims] 1. A stretch-oriented layer having a thickness of 0.1 to 5 μm on a substrate.
m. A ferroelectric polymer liquid crystal device comprising a m ferroelectric polymer liquid crystal layer. 2. A layer stretched and oriented between a pair of substrates having a thickness of 0.1 to 0.1.
2. The ferroelectric polymer liquid crystal device according to claim 1, further comprising a 5 μm ferroelectric polymer liquid crystal layer. 3. The ferroelectric polymer liquid crystal device according to claim 1, wherein said substrate is a plastic substrate. 4. The ferroelectric polymer liquid crystal device according to claim 1, wherein said stretching is performed by stretching a ferroelectric polymer liquid crystal layer and a substrate. 5. The stretching is performed by laminating a ferroelectric polymer liquid crystal layer on a substrate by using any one of blade coating, knife coating, and extrusion coating. The ferroelectric polymer liquid crystal device according to claim 4, wherein the ferroelectric polymer liquid crystal device is formed by co-stretching the layers. 6. The ferroelectric polymer liquid crystal device according to claim 1, wherein said stretching is uniaxial stretching. 7. The ferroelectric polymer liquid crystal device according to claim 6, wherein the stretching ratio of said uniaxial stretching is 10 to 1500%. 8. The ferroelectric polymer liquid crystal device according to claim 6, wherein the stretching ratio of said uniaxial stretching is 20 to 500%. 9. The ferroelectric polymer liquid crystal device according to claim 1, wherein said stretching is sequential biaxial stretching or simultaneous biaxial stretching. 10. The ferroelectric polymer liquid crystal device according to claim 9, wherein the stretching ratio of said biaxial stretching is 1: 1 to 1:50. 11. The ferroelectric polymer liquid crystal device according to claim 1, wherein an electric field is applied simultaneously with said stretching. 12. The ferroelectric polymer liquid crystal device according to claim 1, wherein said stretching is performed in a temperature range not lower than the glass transition point of the ferroelectric polymer liquid crystal.