JPH05257013A - Phase difference plate - Google Patents

Abstract

PURPOSE:To obtain an arbitrary refractive index and dependence on wavelengths and to obtain a sufficient optical compensation effect according to a change, if any in the optical characteristics of a liquid crystal display element by a temp. change by unidirectionally stretching a high-polymer film which is internally dispersed with liquid crystals thereby forming the phase difference plate. CONSTITUTION:The nematic liquid crystals 2 incorporated into the high-polymer film 1 are so oriented that there is no regularity in the orientation of the molecules, such as (A) before the stretching of the film 1 but that the molecules align uniformly along the stretching direction of the film 1 like (B) after the stretching of the film 1. The functions as the phase difference plates are, therefore, added to the film 1 and the internal crystals 2, respectively. Then, the refractive index and the dependence on the wavelengths are largely changed and the arbitrary characteristics are obtd. by selecting the respective materials of the film 1 and the crystals 2 and combining the characteristics thereof. The liquid crystals 2 in the film 1 have the dependence on temps. and, therefore, even if the optical characteristics of the element are changed by the change in the temp., the sufficient optical compensation effect meeting the change is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retardation plate used for optical compensation of a liquid crystal display device.

[0002]

2. Description of the Related Art A retardation plate of this kind is used for optical compensation such as compensation of coloring in STN type liquid crystal display elements. In the past, a polymer film made of a polycarbonate-based synthetic resin was formed as a polymer film. And obtained by stretching this polymer film.

[0003]

The optical characteristic required for the optical compensation function of the retardation film is the refractive index in the three-dimensional direction and its wavelength dependence, but it is formed by stretching a polymer film as in the conventional case. In the retardation plate thus prepared, the refractive index in the three-dimensional direction and its wavelength dependence are determined by the characteristics of only the material, and it is difficult to obtain an arbitrary refractive index and its wavelength dependence.

Further, in the liquid crystal display element, since the refractive index of the liquid crystal has temperature dependency, the optical characteristics change depending on the temperature. On the other hand, in the conventional retardation plate, the refractive index has almost no temperature dependence, and therefore, when the optical characteristics of the liquid crystal display element change due to the temperature change, the optical compensation corresponding to the change is sufficiently performed. There is a difficulty that can not be fulfilled.

The present invention has been made by paying attention to such a point, and an object thereof is to obtain an arbitrary refractive index and its wavelength dependence, and to change the temperature of a liquid crystal display element by changing the temperature. Another object of the present invention is to provide a retardation plate capable of obtaining a sufficient optical compensation effect according to the change even if the optical characteristic changes.

[0006]

In order to achieve such an object, the present invention is one in which a polymer film having a liquid crystal dispersed therein is stretched in one direction to form a retardation plate. ..

[0007]

In the retardation plate having such a structure, the stretching of the polymer film causes the liquid crystal molecules therein to be oriented in the stretching direction. And the optical characteristics of this retardation plate are characteristics obtained by combining the refractive index of the stretched polymer film and its wavelength dependence with the refractive index of the liquid crystal in which molecules are oriented in the stretching direction and its wavelength dependence. ..

The refractive index of the polymer film and its wavelength dependence depend on the material of the polymer film, and the refractive index of the liquid crystal dispersed in the polymer film and its wavelength dependence depend on the liquid crystal material used. .. Therefore, by changing the combination, it becomes possible to greatly change the refractive index of the retardation plate and its wavelength dependence to obtain arbitrary characteristics.

The liquid crystal dispersed in the polymer film is
Since the refractive index has temperature dependence similar to that of the liquid crystal display element, even if the optical characteristics of the liquid crystal display element change due to temperature change, it is possible to obtain a sufficient optical compensation effect according to the change.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment.

In the first embodiment, a nematic liquid crystal 2 is mixed in a transparent polymer film 1 made of a polycarbonate synthetic resin, a polyvinyl alcohol synthetic resin or the like so that the nematic liquid crystal 2 is dispersed almost uniformly. There is. The polymer film 1 is stretched in one direction (the arrow direction in FIG. 1).

The nematic liquid crystal 2 mixed in the polymer film 1 is
As shown in FIG. 1 (A), the orientation of the molecules has no regularity, but after stretching the polymer film 1, the orientation of FIG.
As shown in, the molecules are oriented so as to be aligned substantially uniformly along the stretching direction of the polymer film 1, whereby the polymer film 1 and the nematic liquid crystal 2 inside the polymer film 1 function as retarders. To be equipped.

In the retardation plate having such a constitution, nematic liquid crystal 2 is mixed in a polycarbonate or polyvinyl alcohol resin liquid, and the resin liquid is molded into a film and cured to obtain a polymer film 1, It can be obtained by thermally stretching this polymer film 1 in one direction with a constant load. Next, a second embodiment will be described with reference to FIGS.

In the second embodiment, the liquid crystal capsules 3 are mixed in the polymer film 1 so as to be dispersed almost uniformly, and in this state, the polymer film 1 is unidirectional (see FIG. 2).
In the arrow direction).

As shown in FIG. 3, the liquid crystal capsule 3 has a nematic liquid crystal 2 enclosed in a substantially hollow elliptical capsule 3a made of a transparent material such as a polymer, and the molecules of the nematic liquid crystal 2 are enclosed. Are oriented in the long axis direction of the capsule body 3a.

The liquid crystal capsule 3 mixed in the polymer film 1 has the following properties before the polymer film 1 is stretched.
As shown in FIG. 2 (A), the major axis direction is in an irregular direction, but after stretching the polymer film 1, the major axis direction is high as shown in FIG. 1 (B). Arranged so as to be almost uniformly aligned along the stretching direction of the molecular film 1,
Therefore, the molecules of the nematic liquid crystal 2 in each liquid crystal capsule 3 are almost uniformly oriented along the stretching direction of the polymer film 1, and thus the polymer film 1 and the nematic liquid crystal 2 each have a function as a retardation plate. To be equipped.
The following table shows an example of the optical properties of the polymer film 1 and the nematic liquid crystal 2.

[0017]

[Table 1]

Then, the combination of the characteristics of the polymer film 1 and the characteristics of the nematic liquid crystal 2 shown in this table becomes the characteristics of the retardation plate. That is, the optical properties of the retardation plate are the refractive index of the stretched polymer film 1 and its wavelength dependence,
This is a characteristic in which the refractive index and the wavelength dependence of the nematic liquid crystal 2 dispersed in the polymer film 1 and having the molecules oriented in the stretching direction are synthesized. The refractive index and the wavelength dependence of the polymer film 1 are determined by the material of the polymer film 1, and the refractive index and the wavelength dependence of the nematic liquid crystal 2 dispersed in the polymer film 1 are the liquid crystal used. It depends on the material. Therefore, by changing the combination, the refractive index of the retardation plate and its wavelength dependence can be selected, and thereby the refractive index and its wavelength dependence can be greatly changed to obtain arbitrary characteristics.

Further, since the nematic liquid crystal 2 dispersed in the polymer film 1 has the same temperature dependence of the refractive index as the liquid crystal display element, even if the optical characteristics of the liquid crystal display element change due to the temperature change, It is possible to obtain a sufficient optical compensation effect according to the change.

[0020]

As described above, according to the retardation plate of the present invention, the refractive index and the wavelength dependence thereof are selected by selecting the respective materials of the polymer film and the liquid crystal to be dispersed therein, and combining the characteristics. The liquid crystal dispersed in the polymer film has temperature dependence, so even if the optical characteristics of the liquid crystal display element change due to temperature change, the change can be There is an advantage that a sufficient optical compensation effect can be obtained.

[Brief description of drawings]

1A and 1B show a first embodiment of the present invention, in which FIG. 1A is a sectional view of a polymer film before stretching, and FIG. 1B is a sectional view of the polymer film after stretching.

FIG. 2 shows a second embodiment of the present invention, where (A) is a cross-sectional view of a polymer film before stretching, and (B) is a cross-sectional view of the polymer film after stretching.

FIG. 3 is a cross-sectional view showing a liquid crystal capsule in the second embodiment.

[Explanation of symbols]

 1 ... Polymer film 2 ... Nematic liquid crystal

Claims (1)

[Claims] 1. A retardation plate obtained by unidirectionally stretching a polymer film having a liquid crystal dispersed therein.