JP3506405B2 - Optical element and display device - Google Patents

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, a method for driving the optical element, and a display device.

[0002]

2. Description of the Related Art FIG. 16 shows an outline of an optical element using a holographic polymer dispersed liquid crystal according to a conventional example.

As shown in FIG. 16, a transparent electrode 01 is formed on the surface.
An optical element is formed by using a glass plate 02 having a resin 03 sandwiching a resin 03 so that the electrodes 01 face each other.
The resin 03 has a structure in which liquid crystal particles 04 are periodically distributed. A power source (not shown) is electrically connected to the electrodes 01, 01.

In the above structure, 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 the light of a specific wavelength is reflected due to the interference effect, and the reflected light 06
Then, for example, it enters the eyeball 07, but the light of other wavelengths is transmitted as it is and becomes the transmitted light 08.

When a voltage is applied between the electrodes 01 and 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, so that the scattered light by each liquid crystal grain 04 disappears and the reflected light becomes Disappear.

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

[0007]

However, as shown in FIG.
In the conventional optical element as shown in, since the orientation of the liquid crystal is random at the initial stage, the refractive index difference with the resin is 0.06.
However, there is a problem that the reflection spectrum width is narrow. There is also a problem that the operating voltage is high.

An object of the present invention is to provide an optical element for displaying information with high light utilization efficiency by light, a method of driving the optical element, and a display device.

[0009]

The first optical element of the present invention for solving the above-mentioned problems includes a set of electrodes each provided with an electrode.
What is claimed is: 1.An optical element having a fine periodic structure composed of a translucent material and a variable refractive index material sandwiched between transparent substrates , wherein the variable refractive index material is oriented in a direction substantially parallel to the substrate. Made of smectic liquid crystal with effect,
When an electric field is applied to the smectic liquid crystal by the electrode
It is characterized in that its orientation direction rotates in a plane parallel to the substrate .

[0010]

[0011]

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

The first display device of the present invention is characterized by comprising arranging a plurality of first optical element in a plane.

The second display device of the present invention is characterized by comprising superimposed plural first optical element or the first display device.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below.

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 comprises a resin 13 sandwiched between two glass plates 12 and 12 which are substrates provided with a transparent electrode 11, and in the resin 13, Liquid crystal grains 14 made of liquid crystal aligned in a direction parallel to the glass plate 12 (direction of arrow X) are periodically distributed.

In the present embodiment, the resin 13 is used as the translucent material, and the liquid crystal grains 14 with uniform alignment are used as the refractive index variable material to form the fine periodic structure, and the optical element according to the present embodiment is formed. Are configured.

Incident light 15 from the light source enters the optical element 10.
Is scattered by the liquid crystal particles 14 in the resin 13, but since the liquid crystal region is periodically distributed, only the light of a specific wavelength is reflected by the interference effect to become the reflected light 16. Enter the eyeball 17. On the other hand, light of other wavelengths is transmitted through the resin 13 as it is and becomes 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 with the polymer resin disappears, so that the scattered light from each liquid crystal particle 14 disappears. The reflected light 16 disappears and all becomes transmitted light 18.

In the optical element according to the present invention, liquid crystal particles 1 made of liquid crystal aligned in a direction parallel to the substrate (X direction).
Since 4 is distributed periodically, the difference in refractive index between the liquid crystal and the resin in the reflective state becomes 3 times larger than the conventional one, and as a result, the reflection wavelength width spreads 3 times and the reflection efficiency improves 3 times or more. . Therefore, the thickness for obtaining the same degree of peak reflectance is one-third that of the conventional one, so that the voltage can be lowered.

The reason why the difference in the refractive index between the liquid crystal and the resin in the reflective state becomes three times larger than that in the conventional case will be described below.
Refractive index of the liquid crystal, the long axis of the molecule, different in the short axis direction (referred to as n _e, and n _o.). When the orientation is random, the refractive index of the liquid crystal region is an average value (n _e + n _o ) / 3 (1). Here, by aligning the alignment, the refractive index of the liquid crystal region becomes n _e . Also, the refractive index of resin is usually n.
_Use something equal to _o . Therefore, the difference in refractive index between the resin and the liquid crystal, when the orientation of the liquid crystal is random, the _{(n e -n o) / 3} ··· (2). On the other hand, if the orientation of the liquid crystal is aligned, the _{(n e -n o) ··· (} 3) , and the 3-fold difference in refractive index.

[0027]

EXAMPLES Examples showing the effects of the present invention will be described in detail below. [Embodiment 1] FIG. 2 is a schematic view showing an optical element according to the present embodiment. As shown in FIG. 2, the optical element according to the present embodiment is, for example, ITO (Indium Tin O).
glass plate 12 provided with a transparent electrode 11 such as
Between the two glass plates 12 and 12 and the resin 13
Liquid crystal grains 14 made of liquid crystal aligned in a direction parallel to the glass plate 12 (direction of arrow X) are periodically distributed in the resin 13.

When the incident light 15 from the light source is incident on 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. Light of wavelength 16 is reflected and reflected light 16
Next enters the eyeball 17. On the other hand, the light of the other wavelengths is the resin
It 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 with the polymer resin is eliminated, so that the scattered light from each liquid crystal grain 14 disappears and the reflected light 16 Disappears and all becomes transmitted light 18. In the optical element according to the present embodiment, since the liquid crystal is aligned in parallel with the substrate (X direction), a large difference in refractive index between the resin and the liquid crystal can be obtained, and thus the conventional alignment is not aligned. It is possible to improve the reflection efficiency more than three times.

Next, a method of manufacturing the optical element of this embodiment will be described with reference to FIG. As shown in FIG. 3, between the substrates 22 provided with the electrodes 21, a resin raw material in which a liquid crystal such as a nematic liquid crystal is dissolved in a photocurable resin is put to form a polymer dispersed resin region 23. Form. Interference fringes 26 generated by causing two beams of light 25 emitted from the laser light source 24 to interfere with each other are applied to this. Polymerization of the resin occurs in the antinode portion of the interference fringes 26 where the electric field is strong, and liquid crystal regions are formed by phase separation in the remaining portion, and a desired structure as shown in FIG. obtain.

Next, an example of the method for controlling the orientation of the resin particles will be shown below, but the present invention is not limited to these. <Orientation due to shear stress> As shown in FIG. 4, after the light irradiation, the polymer dispersed resin region 2
By applying horizontal forces F ₁ and F ₂ in different directions as shown by the arrows to the substrates 22 and 22 that face each other with the 3 in between,
A shear region is added to the polymer dispersed resin region 23 to align the orientation. Note that it is sufficient that the orientation of the sheared region is maintained even when a force is applied or when the sheared region is returned to the original state after the force is applied.

<Orientation by Magnetic Field> As shown in FIG. 5, in an operation similar to that of FIG. 3 described above, for example, a magnet 27 is used during laser light irradiation to provide an environment for controlling the orientation of liquid crystal such as a magnetic field. By doing so, the orientation in the polymer dispersed resin region 23 may be aligned.

<Alignment by Liquid Crystal Monomer> A liquid crystal monomer is used as a photo-curable resin, and is in an aligned state before laser light irradiation. A mixture of a liquid crystal monomer and liquid crystal generally exhibits liquid crystallinity. Therefore, by sandwiching this mixture between the substrates subjected to the alignment treatment, the mixture is aligned between the substrates like the liquid crystal. By irradiating with light in this state, the structure can be formed in the oriented state. FIG. 6 shows an outline of the formed structure. As shown in FIG. 6, the polymer dispersed liquid crystal region 31 has a structure in which a liquid crystal 33 is dispersed in a polymerized liquid crystal monomer 32. Both the liquid crystal 33 and the liquid crystal monomer 32 are aligned in the same direction. The arrow A in the drawing
The elliptical part of the part shows the anisotropy of liquid crystal molecules.

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

Further, as an optical element, a transmission type diffraction grating structure 34 having a periodic structure in the in-plane direction as shown in FIG.
May be provided between the substrates 22 and 22 provided with the electrode 21.

The structure may also generally be a hologram. Here, the hologram is, as shown in FIG. 8, irradiation of interference fringes composed of output light 25 of laser light and arbitrary coherent light such as scattered light 42 from an object 41 as shown in the figure. The structure obtained by

In this embodiment, by using a matrix-shaped electrode as the electrode, almost arbitrary image information can be displayed. Here, the matrix-like electrode means an electrode in which a strip-shaped electrode 44 is provided on a substrate 43 as shown in FIG. 9A, for example. Further, as shown in FIGS. 9B and 9C, two substrates 43-1 and 43-2 facing each other are provided.
The electrodes 44-1 and 44-2 provided in the above may be overlapped and used so as to intersect each other. Note that FIG. 9 (c) is shown in FIG. 9 (b).
It is the sectional view which looked at from the horizontal direction.

According to this embodiment, it was possible to realize a monochromatic display device having high reflection efficiency.

In particular, when a liquid crystal having a positive dielectric anisotropy is used as the liquid crystal and is oriented in a direction parallel to the substrate, an element that is in a highly efficient reflection state without an electric field and in a transmission state under an electric field is used. realizable.

When a liquid crystal having a negative dielectric anisotropy is used as the liquid crystal and is oriented in a direction orthogonal to the substrate, an element that is in a transmissive state without a field and in a highly efficient reflective state under an electric field is provided. realizable. In particular, the transmittance can be further improved by making the shape of dispersed liquid crystal particles anisotropic.

[Embodiment 2] FIG. 10 is a schematic view showing an optical element of the present invention. This is obtained by removing the glass plate 12 which is the substrate having the electrodes 11 from the optical element according to the first embodiment shown in FIG. 2 described above. Liquid crystal particles 1 made of liquid crystal aligned in the X direction in the resin 13 by the device of this example.
It is possible to realize a film hologram in which 4 are periodically distributed and have high reflection efficiency.

[Embodiment 3] FIG. 11 is a schematic view of an optical element according to another embodiment of the present invention. In this embodiment, an electrode that can apply an electric field in the in-plane direction, such as the comb-shaped electrode 51, is used. here,
As shown in FIG. 11A, the comb-shaped electrode is a comb-shaped electrode provided on a substrate.
Substrate 52 with 1-1 and 51-2 so that the teeth of the comb alternate
It is arranged on top. Two comb-shaped electrodes 51-
By applying a voltage to 1, 51-2, an electric field almost parallel to the substrate surface can be generated between the teeth of the comb.
Although FIG. 11A shows a comb having a plurality of teeth, an electric field between two parallel electrodes may be used.

FIG. 11B shows the comb-shaped electrodes 51-1 and 51.
2 shows an outline of an optical element showing a case where -2 is used on both surfaces of a substrate 52 arranged above and below. The polymer dispersed liquid crystal region 53 is sandwiched by comb electrodes. When a voltage is applied between the electrodes while the electrodes are connected to each other, an electric field perpendicular to the substrate is generated, so that the element becomes transparent. On the other hand, when a voltage is applied to both electrodes while the electrodes are connected to each other, an electric field parallel to the surface of the substrate is generated, resulting in a highly efficient reflection state.

FIG. 11C shows the comb-shaped electrodes 51-1 and 51.
-2 on one surface (the substrate 52 on the lower side in the drawing) of the flat electrode 51-
The case where 3 is used for the other surface (the upper substrate 52 in the drawing) is shown. The polymer-dispersed liquid crystal region 53 is connected to the comb-shaped electrodes 51-1 and 51.
-2 and the planar electrode 51-3 are sandwiched between the electrodes, and the electrodes are connected to each other. When a voltage is applied to the electrodes, an electric field perpendicular to the substrate is generated, so that the element becomes transparent. On the other hand, when a voltage is applied between the electrodes, an electric field parallel to the surface of the substrate is generated, resulting in a highly efficient reflection state.

In particular, by using a substance having a birefringence such as a liquid crystal monomer as the polymer resin, in the state where no electric field is applied, as shown in FIG. Since it acts as a uniform birefringent plate, it transmits all the light, but when an electric field is applied,
As shown in FIG. 2, the polymer dispersed liquid crystal region 31 has a structure in which the liquid crystal 61 is dispersed in the polymerized liquid crystal monomer 32. Since the birefringence axis of the liquid crystal 61 and the birefringence axis of the resin are not parallel to each other, all polarized light is reflected. When the angle formed by the axes of birefringence is 90 degrees, the reflection efficiency becomes maximum.

[Fourth Embodiment] FIG. 13 is a schematic view of an optical element according to another embodiment of the present invention. As shown in FIG. 13 (a), the optical element has an alignment in a direction substantially parallel to the substrate in a resin sandwiched between transparent substrates such as glass plates provided with electrodes such as ITO. It has a structure in which smectic liquid crystal grains 19 exhibiting an electroclinic effect are periodically distributed. The electroclinic effect refers to a property that, when an electric field is applied to liquid crystal, liquid crystal molecules are tilted by an angle proportional to the electric field with the electric field direction as an axis. When an electric field is applied to an optical element having a structure in which smectic liquid crystal particles exhibiting this electrotilt effect are periodically distributed, the orientation direction rotates in a plane parallel to the substrate due to the electrotilt effect. Of the incident light, the light parallel to the alignment direction of the liquid crystal is scattered by the liquid crystal grains in the element, only the light of a specific wavelength is reflected and becomes the reflected light, and the light of other wavelengths is transmitted as it is and the transmitted light. Become. Light polarized perpendicular to the alignment direction of the liquid crystal is not scattered by the liquid crystal particles, and therefore all of the light is transmitted. The optical element of the present embodiment can control the polarization method refractive index of light reflected by an electric field.

Further, as shown in FIG. 13B, by providing the polarizing plate 20 on the optical element, an optical element whose reflected light intensity can be controlled by an electric field can be realized. In particular, when a substance having birefringence such as a liquid crystal monomer is used as the polymer resin, in a state where no electric field is applied,
As shown in FIG. 6, since they are oriented in the same direction, the whole acts as a uniform birefringent plate, so that all light is transmitted, but when an electric field is applied, as shown in FIG. ,
Since the birefringent axis of the liquid crystal 61 and the birefringent real of the resin are not parallel to each other, all polarized light is reflected. When the angle formed by the axes of birefringence is 90 degrees, the reflection efficiency becomes maximum.

[Embodiment 5] Another embodiment of the optical element having the structure shown in FIG. 2 is shown in which a dual frequency liquid crystal is used as the liquid crystal region. The orientation in the initial state is arbitrary. In the dual frequency liquid crystal, the sign (positive / negative) of the dielectric anisotropy changes depending on the frequency of the applied electric field. Therefore, it is possible to realize a transparent state by applying an electric field having a frequency such that the dielectric anisotropy becomes positive, and to realize a highly efficient reflection state by applying an electric field having a frequency such that the dielectric anisotropy becomes negative.

In all the embodiments described above, the first embodiment
Similarly to the above, the distribution of the liquid crystal particles may be a transmission type diffraction grating or a hologram.

In all the embodiments, the periodic structure does not have to be composed of a spherical liquid crystal particle distribution. For example, in FIG.
A multi-layered periodic structure in which a plurality of resin layers 62 and liquid crystal layers 63 are laminated as shown in (a) may be used. In addition, FIG.
Liquid crystal particles 6 arranged in the resin layer 64 as shown in FIG.
5 may have a flat shape. Further, the translucent substance may be periodically divided in the liquid crystal instead of forming the particles by the liquid crystal.

The elements of all the examples of the present invention are shown in FIG.
By arranging a plurality of elements 72 on the substrate 71 as shown in (a), a display device can be formed. In all of the elements of the present invention, as shown in FIG. 15B, a plurality of elements (for example, blue) 72-1, elements (for example, green) 72-2, and elements (for example, red) 72-3 are laminated. Thus, multicoloring is possible.

[0052]

As described above in detail with the embodiments, according to the present invention, an element for displaying information with high light utilization efficiency can be realized. Further, by using the polymer resin, it is possible to give the element variable form (flexibility). The present invention makes it possible to reduce the operating voltage of the device.

[Brief description of drawings]

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

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

FIG. 3 is a schematic view of manufacturing an optical element according to Example 1.

FIG. 4 is a schematic view of an example in which the optical element according to Example 1 is oriented.

FIG. 5 is a schematic view of another example in which the optical element according to Example 1 is oriented.

FIG. 6 is a schematic view of a liquid crystal state of the optical element according to the first embodiment of the present invention.

FIG. 7 is a schematic diagram of a diffraction grating of the optical element according to the first example of the present invention.

FIG. 8 is a schematic diagram of a hologram of the optical element according to the first embodiment of the present invention.

FIG. 9 is a schematic view of an optical element using a matrix electrode according to the first embodiment of the present invention.

FIG. 10 is a schematic view of an optical element according to Example 2 of the present invention.

FIG. 11 is a schematic view of an optical element according to Example 3 of the present invention.

FIG. 12 is a schematic view of an optical element according to Example 3 of the present invention.

FIG. 13 is a schematic view of an optical element according to Example 4 of the present invention.

FIG. 14 is a schematic view of an optical element according to Example 5 of the present invention.

FIG. 15 is a schematic view of a display device of the present invention.

FIG. 16 is a schematic view of an optical element according to the related art.

[Explanation of symbols]

11 Transparent electrode 12 glass plates 13 resin 14 Liquid crystal grains 15 incident light 16 reflected light 17 Eyeball 18 transmitted light

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-10-48605 (JP, A) JP-A-10-68933 (JP, A) JP-A-5-181403 (JP, A) JP-A-5- 181402 (JP, A) JP 5-165009 (JP, A) JP 6-294952 (JP, A) JP 5-11235 (JP, A) JP 5-142580 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/13 G02F 1/1347

Claims (3)

(57) [Claims] 1. A set of transparent substrates each provided with an electrode.
An optical element comprising a fine periodic structure consisting of a transparent material sandwiched plate with the index variable material, electroclinic said index variable material is aligned orientation in a direction substantially parallel to the substrate
Made of smectic liquid crystal that has an effect,
When an electric field is applied to the smectic liquid crystal, its orientation
An optical element whose direction rotates in a plane parallel to the substrate . 2. A display device comprising a plurality of the optical elements according to claim 1 arranged in a plane. 3. A display apparatus characterized by comprising superimposed plural display devices of the optical element or claim 2 of claim 1, wherein.