TW201512707A - Color filter - Google Patents

Abstract

The invention is related to the use of liquid-crystal material with blue phase as the main material to fabricate a transmission and reflection filter. The liquid-crystal material was put between two glassed with transparent conductive films to form a cell. When a voltage was applied into the cell, the wavelengths and intensity of transmission and reflection can be switched.

Description

Filter

The present invention is a filter, in particular, a liquid crystal mixture in a blue phase as a filter for controlling the transmitted light and reflected light intensity or optical band.

The blue phase state is a self-aggregating three-dimensional photonic crystal structure, which appears in a narrow temperature range between the isotropic phase and the Cholesteric phase of the liquid crystal mixture (0.5 to 2 ^0). C). The main forms of the blue phase are divided into three types. According to the occurrence temperature, the first blue phase state BP I, the second blue phase state BP II and the third blue phase state BPIII are respectively.

The liquid crystal mixture of the third blue phase BPIII is an amorphous structure, and the liquid crystal mixture of the second blue phase BPII and the first blue phase BPI is a simple cubic and a body centered cubic structure, respectively. . Since the arrangement of the liquid crystal molecules has a self-assembled three-dimensional periodic structure and a lattice period of about several hundred nanometers when the liquid crystal mixture is in a blue phase state, it has the characteristics of Bragg Reflection. Under the application of an applied voltage, a director change including a crystal lattice or a molecule, a lattice deformation, a phase transition, and the like are caused.

The addition of a light-emitting substance (Chiral Dopant) to the liquid crystal mixture can induce or enhance the helicity of the liquid crystal material, thereby causing the liquid crystal molecules to produce a Helical Structure in the arrangement. When the amount of optically active substance added reaches a certain proportion range, according to the Landau free energy theory, the phase transition of the substance exists in the process of cholesterol phase-blue phase-liquid state.

The contribution of the optically active substance to the liquid crystal is to provide the helical torsional force, but more correctly, the optically active substance actually provides periodic regularity in the spatial structure of the liquid crystal; the liquid crystal of the one-dimensional arrangement of the director is a cholesterol phase state after the addition of the optically active substance. That is, the liquid crystal molecules produce a spiral arrangement in a single direction; when the liquid crystal has a high optical rotation, the liquid crystal molecules are changed from a single-direction spiral arrangement to a double-helical cylinder structure (DTC), which is a liquid crystal. The molecules are spiraled in two orthogonal directions. These double-helical cylinders may be stacked in space, causing Disclination, or may be randomly dispersed in space. At this time, the phase state of the liquid crystal is defined as blue phase. state.

When the liquid crystal mixture is in the blue phase, it has been considered as the main material of the display. It must use the electrode design to generate an electric field parallel to the substrate to induce the complex refractive index of the blue phase liquid crystal to change from zero to a non-zero value, that is, to make the liquid crystal It has birefringence in the blue phase state, and two mutually orthogonal polarizers are added before and after the liquid crystal display device, so that the light penetrates the display device to produce a change of fast bright and dark state, which can be used as an optical switch device.

In many optical systems, two kinds of filters are often used: one is to change the light intensity after the light passes through the filter, but the light band is not particularly limited, which is also called a light-reducing film; the other is to change the light through the filter. After the light band, but usually accompanied by a certain proportion of light intensity reduction, the above two filters are only suitable for the light incident through the filter erection.

The use of a cholesterol phase liquid crystal as a material for a filter can be used as both a reflective and a transmissive filter. When light enters the cholesterol phase liquid crystal filter, the optical band that penetrates the cholesterol phase liquid crystal filter and the light band that is reflected by the cholesterol phase liquid crystal filter complement each other, that is, a visible light (400 nm - 800 nm) After entering the cholesterol phase liquid crystal filter, the intensity of the transmitted light will be 50% of the original incident light intensity. If the transmitted light band is 500 nm–600 nm, the reflected light band will be 400 nm–500 nm, 600. A mixture of nm–800 nm and 50% light intensity from 500 nm to 600 nm. The wavelength of the reflected light can be modulated by changing the pitch length of the liquid crystal of the cholesterol phase, and the pitch is changed by adjusting the optical rotation of the liquid crystal of the cholesterol phase, controlling the temperature of the liquid crystal of the cholesterol phase, and applying the voltage to the liquid crystal of the cholesterol phase. In addition, the wavelength of the reflected light can be modulated by changing the direction in which the light is incident on the liquid crystal filter of the cholesterol phase.

For example, by adjusting the pitch of the liquid crystal of the cholesterol phase by means of an applied voltage, the time required for the modulation to change the reflected light band is about 10 ms to 100 ms.

In the current filter, whether using polymer materials, dye molecules or cholesterol phase liquid crystal as the material of the filter, the following objectives cannot be achieved at the same time: one is to use the applied voltage, and at the same time, to modulate the reflected light and wear The light-transmitting light band makes the two light bands the same, but has no effect on the light intensity; the other is that the applied voltage can be used to modulate the intensity of the two lights simultaneously in the fixed reflected light and the transmitted light band.

Therefore, the inventors of the present invention have been designing such patents in view of the above-mentioned application objectives, collecting relevant materials, evaluating and considering various parties, and accumulating years of experience in the industry, through continuous trial and modification. .

The main object of the present invention is to provide a novel filter which, when affected by an electric field, can simultaneously make the light in the direction of the liquid crystal and the light reflected in the direction of the liquid crystal reach the optical band, and the light intensity will change or light. The band changes, the light intensity does not change, and at the same time, the filter takes a long time to change the light band or intensity of the transmitted light and the reflected light, and can be used as a filter.

In order to achieve the above object, the present invention is achieved by the following technical means, wherein the filter of the present invention comprises: a first electrode; a second electrode facing and parallel to the first electrode; and a liquid crystal mixture layer, Is a blue phase; wherein a voltage is applied to the first electrode and the second electrode to form an electric field of the vertical liquid crystal mixture layer, but the electric field direction is not limited to the vertical liquid crystal mixture layer, but may be combined with the liquid crystal mixture layer and the first electrode Or the normal electrode of the second electrode is clamped from 0 to 360 degrees; the electric field can change the molecular arrangement of the liquid crystal mixture layer such that the light penetrates the liquid crystal mixture layer and the light is reflected by the liquid crystal mixture layer.

According to the present invention, the liquid crystal mixture is placed in two substrates having a conductive film, and the electrodes are arranged in parallel to each other. The molecular arrangement of the liquid crystal is changed by means of an applied voltage, so that the wavelength or intensity of the transmitted light and the reflected light are changed to achieve the function of filtering.

The above described objects, features, and advantages of the invention will be apparent from the description and appended claims

10‧‧‧LCD mixture filter

11, 13‧‧‧ substrate
12, 14‧‧‧ conductive film
15‧‧‧Blue phase liquid crystal layer
112, 134‧‧‧ conductive plates

The first figure is a schematic diagram of a blue phase liquid crystal mixture layer of a filter according to an embodiment of the present invention.
The second figure shows the effect of the filter of an embodiment of the present invention on different liquid crystal mixtures and optically active substances.
The third figure shows the relationship between the phase transition temperature and the concentration of the optically active substance of the liquid crystal mixture according to an embodiment of the present invention.
The fourth figure is a variation of the light intensity and the optical band of the negative blue liquid crystal mixture in the third blue phase state BPIII under various voltages according to an embodiment of the present invention.
The fifth figure is the time required for the negative liquid crystal mixture to switch between different light intensities in the third blue phase BPIII according to an embodiment of the present invention.
The sixth figure is a variation of the positive blue liquid phase mixture in the third blue phase state BPIII at various voltages (A) optical band and (B) light intensity according to an embodiment of the present invention.

The present invention is further described in the following with reference to the embodiments of the present invention, but the embodiments are not intended to limit the scope of the present invention, and the description of the operation of the structure is not intended to limit the order of execution thereof. The recombined structure, which produces equal devices, is within the scope of the present invention.

The optical filter of the present invention has a plurality of lattices between two conductive plates to accommodate a liquid crystal mixture layer in the grid, and each grid containing the liquid crystal mixture is called a liquid crystal mixture cell, and the liquid crystal mixture is blue. a phase in which the liquid crystal mixture may be a positive liquid crystal mixture, a negative liquid crystal mixture, a mixture of a liquid crystal and an optically active substance, a mixture of a high molecular polymer and a liquid crystal, or a mixture of a liquid crystal and a high molecular polymer and an optically active substance. It is well known to those of ordinary skill in the art and will not be described again.

Please refer to the first figure for the liquid crystal blue phase of the filter of the present invention. The liquid crystal blue cell 10 includes two conductive plates 112, 134. The conductive plate 112 is composed of a substrate 11 and an electrode 12. The other conductive plate 134 is composed of a substrate 13 and an electrode 14. Two conductive layers are formed. The parallel arrangement of the plates 112, 134 gives the best results, but is not a limitation. In an embodiment, the electrode may be a transparent conductive film, such as indium tin oxide or the like, or may be an opaque conductive film, such as a conductive metal material such as gold, silver or aluminum; and the substrate 11, 13 may be a glass substrate. Or plastic substrate.

In one embodiment, the electrode 12 is connected to the positive electrode of a voltage source (not shown), and the electrode 14 is connected to the negative electrode of the voltage source. Wherein, the voltage source can be direct current or alternating current, and if it is alternating current, the frequency can be unlimited.

There is a liquid crystal mixture layer 15 between the two electrodes 12, 14 which is evenly distributed between the electrodes 12, 14 to form a filter layer. The positive and negative electrodes of the voltage source are connected to the electrode 12 and the electrode 14 to form an electric field of the vertical liquid crystal mixture layer 15, but the electric field direction is not limited to the vertical liquid crystal mixture layer, but may be combined with the liquid crystal mixture layer, the electrode 12 or the electrode 14. The normal clip is 0 to 360 degrees; the electric field can change the molecular arrangement of the liquid crystal mixture layer 15 so that the light penetrates the liquid crystal mixture layer 15 and the light is reflected by the liquid crystal mixture layer 15 to change the optical band or the intensity of the light, and the angle of the reflected light The range is from -180 degrees to 180 degrees.

Referring to the second figure, in an embodiment, the liquid crystal mixture layer 15 is in an amorphous blue phase state, which is affected by a vertical electric field and can significantly increase or decrease reflected light and penetration between milliseconds (ms). The intensity of the light, and the wavelength of the reflected and transmitted light, is only a nanometer displacement, and almost no change in color. The contents of the center wavelength position corresponding to the color of the second figure are as follows:

According to the above, the liquid crystal mixture layer 15 is doped with a specific ratio of chiral dopant S811 (Adrich), that is, between 16% by weight and 30% by weight, so that the liquid crystal mixture layer 15 has a blue phase. Please refer to the third figure for the relationship between the phase transition temperature of the liquid crystal mixture and the concentration of the optically active substance in the present invention. When the optically active substance incorporation ratio is greater than 23% by weight, the temperature range of the first blue phase state will vary with the concentration of the optically active substance. The enlargement increases from 3 degrees to 3 degrees; when the ratio of the optically active substance is more than 25% by weight, the temperature of the third blue phase increases from 0.5 degrees to 2 degrees. The temperature range of the second blue phase is gradually reduced as the optically active substance is added. When the concentration of the optically active substance is higher than 24.5 wt%, the liquid crystal mixture does not have the second blue phase. Wherein, the first blue phase state and the second blue phase state are blue phase states having a lattice structure, and the third blue phase state is a blue phase state of the amorphous lattice structure.

In another embodiment, other optically active materials, such as ZLI4572 (Merck), are added to the liquid crystal mixture, ie, 6 wt% to 20 wt% by weight, so that the liquid crystal mixture layer is provided with a blue phase condition.

Referring to the fourth figure, in one embodiment, a 30 wt% ratio of optically active substance S811 is added to the negative dielectric anisotropic liquid crystal mixture, and the liquid crystal mixture is in a third blue phase state at a specific temperature interval, when the electric field is increased. The reflection and transmission spectra of the liquid crystal mixture are also enhanced. When the voltage is applied to 40 V, the light intensity is saturated. As shown in the third figure, the light band is not significantly changed. Furthermore, since the half-peak full width value (FWHM) D1 of the optical band in the third blue phase state continuously decreases as the voltage increases, it means that the reflected light can be purified and enhanced when the voltage is increased to the liquid crystal mixture layer. Light transmissive color. The fifth graph shows the reaction time of the liquid crystal mixture in the third blue phase, which is shown to be only a few milliseconds.

Referring to the sixth figure, in one embodiment, a 30 wt% ratio of optically active substance S811 is added to the positive dielectric anisotropic liquid crystal mixture, and the liquid crystal mixture is in a third blue phase state, and the electric field increases the reflection of the liquid crystal mixture. The penetration spectrum will also be weakened. When the voltage is applied to 40 V, the light intensity is saturated. As shown in the third figure, the light band is not significantly changed.

In one embodiment, the operating voltage of the liquid crystal mixture used on the filter is related to the dielectric anisotropy of the liquid crystal mixture. The smaller the absolute value of the dielectric anisotropy, the smaller the voltage that changes the light intensity.

In one embodiment, a 30 wt% ratio of optically active material S811 is added to the liquid crystal mixture, which has a lattice phase blue phase, that is, a first blue phase state or a second blue phase state; The reflection and transmission wavelengths of the liquid crystal mixture change.

It is known that when the liquid crystal of the cholesterol phase (ChLC) is affected by the electric field, the wavelength of the reflected light will change, and the light intensity will be reduced, and the full width value Dl of the reflected light will be widened. This characteristic makes it suitable for being adjustable. a wavelength reflector, but the reflected light and the transmitted light have different complementary optical colors; and the liquid crystal mixture used in the present invention can make the reflected light have the same wavelength as the transmitted light, and can be simultaneously affected by the electric field. Changing the transmitted light and the reflected light so that the optical band does not change, the light intensity changes, or the optical band changes, the light intensity does not change, and can be used as an electrically controlled penetration and reflection multiplex filter.

The above embodiments are merely illustrative of the principles and effects of the invention and are not intended to limit the invention. Modifications and variations of the above-described embodiments can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, the scope of the invention should be as set forth in the appended claims.

10‧‧‧LCD mixture filter

11, 13‧‧‧ substrate

12, 14‧‧‧ conductive film

15‧‧‧Blue phase liquid crystal layer

112, 134‧‧‧ conductive plates

Claims (20)

A filter comprising: a first electrode; a second electrode; and a liquid crystal mixture in a blue phase; wherein an electric field is formed between the first electrode and the second electrode to cause the liquid crystal mixture The wavelength, intensity, or band and intensity of a transmitted light and a reflected light formed by penetrating and reflecting an incident light are respectively changed. The filter of claim 1, wherein the second electrode face faces the first electrode and is arranged in parallel with the first electrode. The filter of claim 1 or 2, wherein the first electrode and the second electrode are transparent conductive films. The filter of claim 1 or 2, wherein the first electrode is formed on a first substrate and the second electrode is formed on a second substrate. The optical filter of claim 4, wherein the first substrate and the second substrate are glass substrates or plastic substrates. The filter of claim 1, wherein the liquid crystal mixture comprises a positive liquid crystal mixture or a negative liquid crystal mixture. The filter of claim 1, wherein the liquid crystal mixture comprises a high molecular polymer. The filter of claim 1, wherein the liquid crystal mixture comprises an optically active substance. The filter of claim 8, wherein the doping concentration of the optically active substance affects a temperature range of the blue phase of the liquid crystal mixture. The filter of claim 8, wherein the optically active substance has a doping concentration of 16 to 32 weight percent. The filter of claim 1 or 8, wherein the liquid crystal mixture incorporates a specific ratio of optically active material to reflect or pass light of the particular wavelength. The filter of claim 1, wherein the electric field direction is 0 to 360 degrees from a normal of the liquid crystal mixture, the first electrode or the second electrode. The filter of claim 1, wherein the transmitted light and the reflected light band are in the same band. The filter of claim 1, wherein the blue phase comprises a blue phase having a lattice structure. The filter of claim 14, wherein the blue phase of the lattice structure changes the wavelength of the reflected or transmitted light at an applied voltage. The filter of claim 1, wherein the blue phase comprises a blue phase of the amorphous germanium structure. The filter according to claim 16, wherein the blue phase of the amorphous structure allows the reflected light or the transmitted light to change in light intensity at a specific wavelength band under an applied voltage. The filter of claim 1, wherein the electric field is operable to control the liquid crystal mixture to reflect or pass light of the characteristic band. The filter of claim 1, wherein the angle of the reflected light comprises -180 degrees to 180 degrees. The filter of claim 1, wherein the first electrode or the second electrode is an opaque conductive film.