KR100265062B1 - Reflective lcd with conduting polypyrrole - Google Patents

Abstract

PURPOSE: A reflective liquid crystal display device is to include a polypyrrole film capable of replacing an electrode layer, a light absorbing layer and a liquid crystal alignment layer of the liquid crystal display device. CONSTITUTION: The liquid crystal display device includes an upper glass substrate(2), a lower glass substrate(12) opposed to the upper glass substrate, a transparent electrode film(4) applied on an inner surface of the upper glass substrate, and a liquid crystal alignment film(6) formed on the transparent electrode film, an electrical conductive polypyrrole film(10) formed on an inner surface of the lower glass substrate, and a liquid crystal layer(8) disposed between the electrical conductive polypyrrole film and the liquid crystal alignment film. If the liquid crystal in the liquid crystal layer is in a planar state, the polypyrrole film reflects a visible ray of a specific wavelength, so that the reflected color is viewable.

Description

Liquid Crystal Display Device Containing Electroconductive Polypyrrole Film

The present invention relates to a liquid crystal display device containing an electrically conductive polypyrrole film, and in particular, a liquid crystal containing an electrically conductive polypyrrole film capable of simultaneously replacing an electrode layer, a light absorbing layer, and a liquid crystal alignment film layer of an existing device with an electrically conductive polypyrrole film. It relates to a display element.

According to the present invention, the polypyrrole film is coated on a glass substrate so that the user can process it into a required shape, and thus the electrode layer, the light absorbing layer, and the liquid crystal alignment layer of the liquid crystal display device are simultaneously replaced by using the polypyrrole film on the glass substrate. An object of the present invention is to provide a liquid crystal display device containing an electrically conductive polypyrrole film which can be increased.

1 is a graph showing the change of the surface resistance according to the thickness of the polypyrrole film.

2A and 2B are schematic views showing a chiral nematic liquid crystal display device according to the present invention.

3A and 3B are schematic views showing a polymer dispersed liquid crystal display device according to the present invention.

Figure 4 is a graph showing the reflection spectrum of the chiral nematic liquid crystal display device according to the present invention.

5 is a graph showing the reflection spectrum of the chiral nematic / polymer dispersed liquid crystal display device according to the present invention.

6 is a graph showing the range of the switching voltage by the alternating current of the chiral nematic / polymer dispersed liquid crystal display device according to the present invention;

<Explanation of symbols for the main parts of the drawings>

2: upper glass substrate 4: transparent electrode film

6: liquid crystal aligning film 8: liquid crystal layer

10: polypyrrole film 12: lower glass substrate

14: upper glass substrate 16: transparent electrode film

18: composite film layer 20: polypyrrole film

22: lower glass substrate

The liquid crystal display device containing the conductive polypyrrole film of the present invention includes an upper glass substrate, a lower glass substrate formed to face the upper glass substrate, a transparent electrode film coated on an inner surface of the upper glass substrate, and And a liquid crystal layer formed between the liquid crystal alignment film formed on the transparent electrode film, the electrically conductive polypyrrole film formed on the inner surface of the lower glass substrate, and between the electrically conductive polypyrrole film and the liquid crystal alignment film.

The liquid crystal display device containing the electrically conductive polypyrrole film of the present invention configured as described above will be described in detail with reference to the accompanying drawings.

Using the glass substrate attached to the inner surface of the electrically conductive polypyrrole film produced by the manufacturing method of the present invention, the following liquid crystal display device is provided.

1 is a graph showing a change in the surface resistance according to the thickness of the polypyrrole film, Figures 2a, 2b is a schematic diagram showing a chiral nematic liquid crystal display device according to the present invention, Figures 3a, 3b is a polymer according to the present invention 4 is a schematic diagram illustrating a dispersed liquid crystal display device, and FIG. 4 is a graph showing a reflection spectrum of a chiral nematic liquid crystal display device according to the present invention, and FIG. 5 is a reflection spectrum of a chiral nematic / polymer dispersed liquid crystal display device according to the present invention. 6 is a graph showing the range of the switching voltage by the alternating current of the chiral nematic / polymer dispersed liquid crystal display device according to the present invention.

Multi-stable chiral nematic display device using the chiral nematic or cholesteric liquid crystal (US Patent No. 5,453,863), polymer stabilized cholesteric texture (PSCT) display device (US Patent No. 5,437,811) And JW Doane, D.-K. Yang, and Z, Yaniv, Jpn. Display, 9, 73 (1992) and polymer dispersed chiral liquid crystal display devices (US Pat. Nos. 5,251,048 and JL West, J. Francl). , and JW Doan, Appl. Phys. Lett., 63, pp.1471 to 1473 (1993)), utilize the bistable stability of chiral nematic liquid crystals and are visible in focal conic states. This bistable stability is used because the light is scattered lightly and becomes almost transparent, and in the planar state, it has a characteristic of reflecting visible light of a specific wavelength depending on the pitch of the chiral nematic liquid crystal layer. Memory type and low power consumption type liquid crystal display To may be used.

In addition, since the liquid crystal display devices are oriented in the direction of the electric field when the electric field is applied, the liquid crystal display devices are driven by continuous switching using the contrast of the transparent state in the presence of the electric field, that is, the homeotropic state and the planar state when the electric field is removed. A display element can be manufactured.

In the above display elements, when black is displayed in a focal conic or homeotropic state, a black / specific color contrast can be obtained along with a specific color reflection in a flannel state. Coating is used (see T. Uchida, SID 96 Digest, pp. 31-34 (1996)).

Therefore, as an embodiment of the present invention, a cross-sectional structure of a chiral nematic (cholesteric) liquid crystal display device having a novel structure by the polypyrrole film of the present invention as shown in FIGS. 2A and 2B is shown. (2), the lower glass substrate 12 formed to face the upper glass substrate 2, the transparent electrode film 4 formed on the inner surface of the upper glass substrate 2, and the transparent electrode film. (4) the liquid crystal alignment film 6 formed on the surface, the electrically conductive polypyrrole film 10 formed on the inner surface of the lower glass substrate 12, and between the electrically conductive polypyrrole film 10 and the liquid crystal alignment film 6 In this configuration, the liquid crystal layer 8 containing the chiral nematic liquid crystal is formed.

In the above structure, the polymer material may be mixed in the liquid crystal layer 8, and when the liquid crystal is in the plane state, the polypyrrole film 10 of black color is visible from the outside because the visible light of a specific wavelength is reflected depending on the pitch of the liquid crystal. When the reflected color is visible but is in the focal conic state, the size of each focal conic domain is shorter than the wavelength of visible light, so the visible light is almost transmitted and thus the polypyrrole film coated on the inner surface of the lower glass substrate 12 The black color in (10) is shown as it is.

Accordingly, the polypyrrole film 10 simultaneously serves as an electrode and a light absorbing plate.

In addition, when the liquid crystal needs to be pre-oriented to improve contrast or stability, the liquid crystal may be oriented in the friction direction by using a method of rubbing the surface of the polypyrrole film 10 with a cloth such as nylon or rayon, which is mainly used in conventional polyimide alignment films. It also has the function of the alignment film to be oriented.

The liquid crystal aligning film 6 coated on the transparent electrode film 4 also has alignment performance by the friction method and may be omitted when the function of the alignment film is not important because a large amount of polymer material is incorporated in the liquid crystal layer.

As another embodiment of the present invention, the polymer dispersed liquid crystal display device using the polypyrrole film produced by the above manufacturing method, a polymer liquid crystal display device in which nematic liquid crystal droplets are dispersed in a polymer base (US Patent No. 4,688,900). And 5,264,950, the present invention is a new structure in which the electrically conductive polypyrrole film is present on the inner surface of one substrate, as shown in FIGS. 3A and 3B.

The transparent electrode film 9 is coated on the inner surface of the upper glass substrate 14 and the lower glass substrate 22 disposed to face each other.

An electrically conductive polypyrrole film 20 is formed on the inner surface side of the lower glass substrate 22, and a nematic liquid crystal / polymer composite film layer 18 is formed between the electrically conductive polypyrrole film 20 and the transparent electrode film 9. do.

In addition, when the electric field is not applied, the liquid crystal molecules in each liquid crystal are oriented in different directions, and when the size of the liquid crystal droplets is adjusted to scatter visible light, almost no light reaches the polypyrrole film 20 so that white Will appear.

However, when an electric field is applied, the liquid crystal molecules in each liquid crystal are oriented in the electric field direction. If the liquid crystal and the polymer material are selected so that the refractive index of the polymer base (η _P ) and the molecular perpendicular direction of the liquid crystal (η _O ) coincide with each other. The visible light is transmitted through the nematic liquid crystal / polymer composite film layer 18 without being scattered and then absorbed by the surface of the polypyrrole film 20 so that it appears black.

Accordingly, black / white contrast can be obtained by applying and removing the electric field, and the polypyrrole film 20 simultaneously serves as an electrode and a light absorbing layer.

In addition, the thickness of the polypyrrole film 20 can be controlled by changing the concentration of the solution, the rotational speed during spin casting, etc. As shown in FIG. 1, the surface resistance is inversely proportional to the film thickness.

Example 1

The glass substrate with the polypyrrole film was measured with a depth profiler. As a result, the thickness of the polypyrrole film was 3.1 μm and the smoothness of the film surface measured by the atomic force microscope was within 0.01 μm. The obtained surface conductivity was 2.8 kW / square.

The liquid crystals E63 and K15 (BDH UK) were contacted on the polypyrrole film and allowed to stand at 20 to 80 ° C for 24 hours. As a result of observation, no signs of polypyrrole dissolved in the liquid crystal were found.

Example 2

The liquid crystal layer having a thickness of 11 μm using the glass substrate chiral nematic liquid crystal mixture (CE: 21 wt%, CB: 21 wt%, E48: 58 wt%, above, manufactured by Merk, Germany) with a polypyrrole film in Example 1 The display element is formed as shown in FIG. 2, and FIG. 4 shows a portion of the focalconic state generated after removing and applying a 70 V direct current for 20 msec, and a 20 V sec after 130 V direct current is removed. The reflectance spectrum of the generated planar state shows that the part of the planar state reflects about 90% of visible light at wavelength 510 nm, while the part of the focal conic state reflects less than 20% in almost all areas. Could.

Example 3

The chiral nematic liquid crystal mixture and the photocurable polymer precursor NOA65 (Norland, USA) are mixed as a constituent material of the liquid crystal layer at a weight ratio of 80:20, and ultraviolet rays having a wavelength of 365 nm at a intensity of 15 mW / cm ² for 20 minutes at 50 ° C. The following results were obtained by forming and using a chiral nematic liquid crystal / polymer dispersion film cured by irradiation.

Therefore, in the display element shown in Fig. 5, the reflection spectrum of the portion of the focal conic state and the planar state is shown. The portion of the flan state reflects about 35% of visible light having a wavelength of 560 nm, but the portion of the focal conic state is about 11%. It can be seen that only reflects%.

Example 4

The switching effect by alternating current rather than a direct current pulse was measured about the karal nematic / polymer dispersed liquid crystal display element containing a polymer.

As shown in FIG. 6, the reflectance at 560 nm among the reflection spectra of each state obtained after applying and removing a 200 Hz right-angle waveform alternating current for 20 msec is shown according to the change in the applied voltage. When switching is started in the focal conic state, about 100 V When the above alternating current is applied and removed, it is converted into a planar state and reflects visible light. By applying and removing a voltage between 80 and 100 V, intermediate reflection states proportional to the magnitude of the voltage are obtained.

On the other hand, when switching is started in the planar state, the voltage is changed to a focal conic state by applying and removing a voltage between 60 and 80 V, so that visible light is not reflected.

In the voltage range of 0 to 20V, the planar state is maintained. After the voltage is removed, the planar state is returned to the planar state. After the voltage is applied, the voltages of 20 to 60V and 80 to 100V are applied and removed.

Although the present invention has been described as an example by using an electrically conductive polypyrrole film formed on a glass substrate of a liquid crystal display device by way of example, the present invention is not limited thereto and can be applied to various other fields.

By the polypyrrole film of the present invention as described above, the electrode layer, the light absorbing layer, and the liquid crystal alignment film of the conventional liquid crystal display device can be replaced at the same time, thereby simplifying the structure, simplifying the process, and increasing the contrast effect. There is.

Claims (3)

An upper glass substrate 2; A lower glass substrate 12 formed to face the upper glass substrate 2; A transparent electrode film 4 formed on the inner surface of the upper glass substrate 2 by a coating; A liquid crystal alignment film 6 formed on the transparent electrode film 4; An electrically conductive polypyrrole film 10 formed on an inner surface of the lower glass substrate 12; And A liquid crystal layer 8 formed between the electrically conductive polypyrrole film 10 and the liquid crystal alignment film 6, When the liquid crystal in the liquid crystal layer 8 is in a planar state, it reflects visible light having a specific wavelength according to the pitch of the liquid crystal so that the polypyrrole film 10 is not visible from the outside but is reflected in a specific color, and is visible in the focal conic state. Light transmitting the liquid crystal display element using a chiral nematic liquid crystal, characterized in that the visible color of the polypyrrole film 10 is coated on the inner surface of the lower glass substrate (12). 2. The liquid crystal display device according to claim 1, wherein the liquid crystal layer (8) is made of a chiral nematic liquid crystal or a mixture of chiral nematic and a polymer. An upper glass substrate 14; A lower glass substrate 22 formed to face the upper glass substrate 14; The transparent electrode film 16 having a coating formed on the inner surface of the upper glass substrate 14. An electrically conductive polypyrrole film 20 formed on an inner surface of the lower glass substrate 22; And A polymer dispersed liquid crystal display device comprising a nematic liquid crystal / polymer composite film layer 18 formed between the electrically conductive polypyrrole film 20 and the transparent electrode film 16.

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