JPH1090730A - Optical element, its drive method and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical element capable of holding information with high availability of light by having a minute periodical structure consisting of translucent substance and variable refractive index substance and using a smectic liquid crystal as the variable refractive index substance. SOLUTION: This optical element is constituted so as to hold a resin 13 between two sheets of glass plates 12 being a substrate provided with a transparent electrode 11, and liquid crystal particles 14 consisting of the smectic liquid crystal are distributed periodically (in fringe pattern shape) in this resin 13. Since the smectic liquid crystal is used, when it is oriented by an electric field, a layer shape structure in the direction orthogonally intersecting with the oriented direction is formed, and the layer is held even when the electric field is turned off, and a transmission state is stored. Then, when this optical element is heated, the liquid crystal is moved to an isotropic phase with lower viscocity to be restored to an original reflection state. Further, by using a comb type electrode as the electrode 11, the optical element capable of rewriting only by the electric field and holding is obtained, and further, by using a high polymer resin, flexibility is given to the element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element for displaying information by light intensity, an element driving method, and a display device.

[0002]

2. Description of the Related Art FIG. 13 schematically shows an optical element using a holographic polymer-dispersed liquid crystal according to a conventional example.

[0003] As shown in FIG.
An optical element is constituted by using a glass plate 02 having a resin and sandwiching a resin 03 so that the electrodes 01 face each other.
The resin 03 has a structure in which liquid crystal grains 04 of nematic liquid crystal are periodically (striped) distributed. A power supply (not shown) is electrically connected to the electrodes 01 and 01.

In the above configuration, the incident light 05 from the light source
Is scattered by the liquid crystal particles 04 in the resin 03, but since the liquid crystal particles 04 are periodically distributed, only light of a specific wavelength is reflected by the interference effect, and the reflected light 06 is reflected.
Then, for example, the light enters the eyeball 07, but light of other wavelengths is transmitted as it is and becomes the transmitted light 08.

When a voltage is applied between the electrodes 01 of the electric element, the liquid crystal is oriented by the electric field, and the difference in the refractive index from the polymer resin disappears. Disappears.

Conventionally, the presence or absence of the reflected light is used as an element operation of the optical element (IEICE Technical Report EID 95-147, ED9).
5-221, SDM96-261 pp.131-136).

[0007]

However, FIG.
In the conventional optical element as shown in (1), when the power is turned off, the state returns to the transparent state, so that there is a problem that electric power is required to maintain the display contents.

An object of the present invention is to provide an optical element capable of holding information with high light use efficiency, a driving method of the optical element, and a display device.

[0009]

According to a first aspect of the present invention, there is provided an optical element having a fine periodic structure comprising a light-transmitting substance and a variable refractive index material, wherein The variable material is made of a smectic liquid crystal.

A second optical element according to the present invention is characterized in that the first optical element is sandwiched between a pair of electrodes.

[0011] The third optical element of the present invention comprises a first or second optical element.
The optical element according to any one of the above, further comprising a heating means.

A fourth optical element according to the present invention is characterized in that, in the third optical element, the electrodes are arranged in a direction parallel to the substrate.

The first method for driving an optical element according to the present invention is the fourth method for driving an optical element, in which an electric field is applied in the horizontal direction using the above-mentioned electrodes, so that the direction orthogonal to the alignment direction of the liquid crystal is obtained. A layer structure is formed, and the layer structure is maintained even when the electric field is cut off, while being restored by heating.

According to a fifth optical element of the present invention, in the second optical element, the electrode is a comb-shaped electrode.

The second method for driving an optical element according to the present invention is the fifth method for driving an optical element, in which an electric field is applied in a direction perpendicular to the substrate by using the above-mentioned comb-shaped electrodes to thereby align the liquid crystal. A layer structure is formed in a direction perpendicular to the direction, and this layer structure is maintained even when the electric field is cut off, while restoring by applying an electric field in a direction parallel to the substrate using the above-mentioned comb-shaped electrode. .

The first display device of the present invention is characterized in that a plurality of first to fifth optical elements are arranged in a plane.

A second display device according to the present invention is characterized in that a plurality of the first to fifth optical elements or the first display device are stacked.

That is, in the optical element of the present invention,
Since a smectic liquid crystal is used as the liquid crystal, it changes to a transparent state when an electric field is applied, and can maintain its transmission state even when the electric field is turned off. The state is restored.

[0019]

Embodiments of the present invention will be described below in detail.

FIG. 1 is a schematic structure of an optical element according to this embodiment. As shown in FIG. 1, the optical element according to the present embodiment includes a resin 13 sandwiched between two glass plates 12, 12 which are substrates on which a transparent electrode 11 is provided. Liquid crystal grains 14 made of smectic liquid crystal are periodically (striped) distributed.

The optical element 10 has an incident light 15 from a light source.
Is incident, the light is scattered by the liquid crystal particles 14 in the resin 13. However, since the liquid crystal regions are periodically distributed, only light of a specific wavelength is reflected by the interference effect to become reflected light 16. It enters the eyeball 17. On the other hand, light of other wavelengths is transmitted through the resin 13 as it is to become transmitted light 18.

Next, when a voltage is applied between the electrodes 11 of the optical element, the liquid crystal is oriented by the electric field, and the difference in the refractive index from the polymer resin is eliminated. The reflected light 16 disappears. Here, in the present invention, since a smectic liquid crystal is used, a layered structure is formed unlike a conventional nematic liquid crystal. In this way, when oriented by an electric field, a layer structure in a direction orthogonal to the orientation direction is formed, and even when the electric field is turned off, this layer is maintained,
The transmission state is stored. Next, when the optical element is heated, the liquid crystal is transferred to a less viscous isotropic phase, so that the liquid crystal is restored to the original reflection state.

Here, the write voltage is set to about 400 V in the present embodiment, but the present invention is not limited to this.

In the present embodiment, as the resin,
Although a photocurable resin was used, the present invention is not limited to this.

As the smectic liquid crystal used in the present invention, for example, liquid crystals such as "S1, S2, S3 (trade name; manufactured by Merck)" and "K24 (trade name; manufactured by Merck)" can be used. However, the present invention is not limited to this.

The heating temperature in the present embodiment is about the transition temperature of the smectic liquid crystal (about 70 to 120 degrees).
Is generally selected, but is almost arbitrarily selected depending on the material.
In addition, the conditions under which dielectric loss occurs differ depending on various materials. For example, the conditions are about several hundred MHz and about several hundred to several kV, but the present invention is not limited to this.

[0027]

Embodiments of the present invention will be described below in detail.

Embodiment 1 FIG. 2 is a schematic view showing an optical element according to this embodiment. As shown in FIG. 2, the optical element according to the present embodiment is, for example, ITO (Indium).
Two glass plates 12 provided with a transparent electrode 11 such as Tin Oxide are opposed to each other.
A resin 13 is interposed between the resin 13, and liquid crystal grains 14 made of smectic liquid crystal are periodically distributed in the resin 13.

When the incident light 15 from the light source enters this optical element, it is scattered by the liquid crystal particles 14 in the resin 13, but since the liquid crystal region is periodically distributed, it is specified by the interference effect. Is reflected and only reflected light 16 is reflected.
And enters the eyeball 17. On the other hand, light of other wavelengths
The light passes through the inside as it is to become transmitted light 18.

When a voltage is applied between the electrodes 11 of the optical element, the liquid crystal is oriented by the electric field and the difference in the refractive index from the polymer resin is eliminated. Disappears. However, in the optical element according to the present embodiment, since the smectic liquid crystal is used as the liquid crystal particles, this transmission state is maintained even when the electric field is cut off. That is, according to the present embodiment, a monochromatic optical element that holds information displayed without power can be realized.

Next, a method for manufacturing the optical element of this embodiment will be described with reference to FIG. As shown in FIG. 3, a resin material in which a smectic liquid crystal is dissolved in a photocurable resin is placed between substrates 22 provided with electrodes 21 to form a polymer-dispersed resin region 23. Here, the laser light source 2
An interference fringe 26 generated by causing two beams of light 25 emitted from 4 to interfere with each other is irradiated. Polymerization of the resin occurred at the strong antinode portion of the electric field of the interference fringes 26, and the remaining portion formed a liquid crystal region precipitated by phase separation, which was periodically distributed.
A desired structure as shown in FIG. 2 is obtained.

In this embodiment, a glass plate is used as a substrate. However, the present invention is not limited to this.
For example, a plate, a film, or the like made of an organic material such as an acrylic resin may be used. In addition, although ITO was used as the electrode, it is not limited to this.

As an optical element, a transmission type diffraction grating structure 30 having a periodic structure in an in-plane direction as shown in FIG.
May be provided between the substrates 22 provided with the electrodes 21. The above-mentioned transmission type diffraction grating structure refers to a structure having a fine periodic structure in which the exit surface of the transmitted light and the diffracted light is a surface on the opposite side to the exit surface.

The structure may generally be a hologram. Here, the hologram is, as shown in FIG. 5, irradiation of interference fringes composed of laser light output light 25 and arbitrary coherent light such as scattered light 42 from an object 41 as shown in the figure. Means the structure obtained by

In this embodiment, almost any image information can be displayed by using a matrix electrode as the electrode. Here, the matrix electrode refers to an electrode provided with a strip electrode 44 on a substrate 43 as shown in FIG. 6A, for example. As shown in FIGS. 6B and 6C, two opposing substrates 43-1 and 43-2 are provided.
May be used in such a manner that the electrodes 44-1 and 44-2 provided in the above cross each other. FIG. 6 (c) is the same as FIG.
FIG. 3 is a cross-sectional view as viewed from the lateral direction. According to the present embodiment, it was possible to realize a monochromatic display element having high reflection efficiency.

It is to be noted that the display information can be erased by applying a high frequency voltage between the electrodes and raising the temperature by the heat caused by the dielectric loss.

[Embodiment 2] FIG. 7 is a schematic view showing an optical element of the present invention. The optical element according to the first embodiment shown in FIG. 2 is different from the optical element according to the first embodiment in that the glass plate 12 which is the substrate having the electrode 11 is omitted. Omitted. With the element of this embodiment, the orientation of the liquid crystal can be controlled by applying an electric field at the time of preparation, so that it is possible to produce a film having a distribution of diffraction characteristics. With the element of this embodiment, an erasable and non-rewritable film hologram can be realized.

Embodiment 3 FIG. 8 is a schematic view of an optical element according to another embodiment of the present invention. This embodiment is an embodiment in which a lens 31 is provided on the optical element of the first embodiment as a heating unit. Since other configurations are the same as those of the first embodiment, the same members are denoted by the same reference numerals and description thereof will be omitted. As shown in the figure, light 32 such as output light of a semiconductor laser can be focused on a resin region through a lens 31. By applying a voltage to the electrode and condensing and heating light to a part of the region that has transitioned to the transparent state to increase the temperature, it is possible to return the specific part to the reflective state. That is, according to this embodiment, an optical element that can be rewritten and held can be realized.

In particular, by using infrared or ultraviolet invisible light as the light 32 and using a substance that absorbs the light or a dye that absorbs the light in the resin or liquid crystal, the writing light affects the image. Can be prevented.

Embodiment 4 FIG. 9 is a schematic view of an optical element according to another embodiment of the present invention. In this embodiment, the optical element is formed using the temperature control element 40 as the heating means. In the present embodiment, for example, a Peltier element is used as the temperature control element 40, and the optical element 10 of the first embodiment is mounted on the Peltier element.

Also in the present embodiment, writing can be performed by an electric field as in the first embodiment. In addition, the whole can be erased by heating with a temperature control element.
Note that, in the optical element of the present embodiment, after rewriting, an image can be held even if it is separated from the temperature control element 40.
Can be applied as a lightweight image medium.

As a smectic liquid crystal, for example, K
By using an element that exhibits a nematic phase between the smectic phase and the isotropic phase as shown in Fig. 24, and controlling the rewriting temperature to the temperature at which the liquid crystal becomes the nematic phase, this element becomes a normal holographic polymer dispersion. Moving images can be displayed in the same manner as liquid crystals, and only one scene can be recorded by cooling to a smectic phase.

Embodiment 5 FIG. 10 is a schematic view of an optical element according to another embodiment of the present invention. In the present embodiment, for example, a comb-shaped electrode 51 is used instead of the electrode 11 in the first embodiment.
An electrode capable of applying an electric field in the in-plane direction as described above is used, and the same members as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. Here, as shown in FIG. 10A, a comb-shaped electrode is one in which a comb-like electrode is provided on a substrate.
51-2 are arranged on the substrate 52 so that the teeth of the comb are alternately arranged. Two comb-shaped electrodes 51-1 and 51-
By applying a voltage to 2, an electric field substantially parallel to the substrate surface can be generated between the teeth of the comb. FIG.
Although (a) shows a comb having a plurality of teeth, an electric field between two parallel electrodes may be used.

FIG. 10B shows comb-shaped electrodes 51-1 and 51.
The outline of an optical element showing a case where -2 is used on both surfaces of a substrate 52 arranged vertically is shown. The polymer dispersed liquid crystal region 53 is sandwiched between the comb-shaped electrodes. When a voltage is applied between the electrodes while the electrodes are connected, an electric field perpendicular to the substrate is generated, so that the element is in a transparent state. On the other hand, when a voltage is applied to both electrodes in a state where the electrodes are connected, an electric field parallel to the surface of the substrate is generated, so that a reflection state is obtained.

FIG. 10C shows the comb electrodes 51-1 and 51.
-2 on one side (the lower substrate 52 in the figure) and the flat electrode 51-
3 shows a case where 3 is used for the other surface (upper substrate 52 in the figure). The polymer-dispersed liquid crystal region 53 is connected to the comb-shaped electrodes 51-1 and 51-1.
-2 and the plane electrode 51-3, the electrodes are connected to each other, and when a voltage is applied to the electrodes, an electric field perpendicular to the substrate is generated, so that the element is in a transparent state. On the other hand, when a voltage is applied between the electrodes, an electric field parallel to the surface of the substrate is generated, so that a highly efficient reflection state is obtained. According to the present embodiment, unlike the optical element of the above-described embodiment, the transmission and reflection states can be controlled only by the electric field without providing a heating unit. That is, according to this embodiment, an optical element that can be rewritten and held by only the electric field can be realized.

[Embodiment 6] In all of the elements of the present invention, a display device (element array) can be formed by arranging a plurality of elements 62 on a substrate 61 as shown in FIG. [Embodiment 7] As shown in FIG. 12, a device according to all the embodiments of the present invention is formed by stacking a plurality of devices (for example, blue) 71-1, a device (for example, green) 71-2, and a device (for example, red) 71-3. Display device (element array) capable of multi-color display
Can be formed.

[0047]

As described above in detail with the embodiments, according to the present invention, a display element capable of maintaining a display state can be realized. Further, by using a comb-shaped electrode as an electrode, an optical element that can be rewritten and held by only an electric field can be realized. Further, by using a polymer resin, the element can be provided with a variable (flexible) property.

[Brief description of the drawings]

FIG. 1 is a schematic view of an optical element of the present invention.

FIG. 2 is a schematic diagram of an optical element according to Example 1 of the present invention.

FIG. 3 is a schematic view of the production of the optical element according to Example 1.

FIG. 4 is a schematic view of a diffraction grating of the optical element according to the first embodiment of the present invention.

FIG. 5 is a schematic diagram of a hologram of the optical element according to the first embodiment of the present invention.

FIG. 6 is a schematic diagram of an optical element using a matrix electrode according to Example 1 of the present invention.

FIG. 7 is a schematic diagram of an optical element according to Example 2 of the present invention.

FIG. 8 is a schematic diagram of an optical element according to Example 3 of the present invention.

FIG. 9 is a schematic diagram of an optical element according to Example 4 of the present invention.

FIG. 10 is a schematic view of an optical element according to Example 5 of the present invention.

FIG. 11 is a schematic diagram of a display device according to a sixth embodiment of the present invention.

FIG. 12 is a schematic diagram of a display device according to Example 7 of the present invention.

FIG. 13 is a schematic view of an optical element according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Transparent electrode 12 Glass plate 13 Resin 14 Liquid crystal particle 15 Incident light 16 Reflected light 17 Eye 18 Transmitted light

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Shigenobu Sakai 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation

Claims (9)

[Claims] 1. An optical element having a fine periodic structure comprising a translucent substance and a variable refractive index material, wherein said variable refractive index substance is made of a smectic liquid crystal. 2. An optical element comprising the optical element according to claim 1 interposed between a pair of electrodes. 3. The optical element according to claim 1, further comprising a heating unit. 4. The optical element according to claim 3, wherein the electrodes are arranged in a direction parallel to the substrate. 5. The method for driving an optical element according to claim 4, wherein an electric field is applied in a horizontal direction using the electrodes, thereby forming a layer structure in a direction perpendicular to the alignment direction of the liquid crystal. A method for driving an optical element, characterized in that the layer structure is maintained by heating while the layer structure is maintained even after cutting. 6. The optical element according to claim 2, wherein said electrode is a comb-shaped electrode. 7. The method of driving an optical element according to claim 6, wherein an electric field is applied in a direction perpendicular to the substrate using the comb-shaped electrode to form a layer structure in a direction perpendicular to the alignment direction of the liquid crystal. A method of driving an optical element, comprising forming and maintaining this layer structure even when the electric field is cut off, while restoring by applying an electric field in a direction parallel to the substrate using the comb-shaped electrode. 8. A display device comprising a plurality of optical elements according to claim 1 arranged in a plane. 9. A display device comprising a plurality of the optical elements according to claim 1 or 4 or a plurality of the display devices according to claim 8.