KR101892568B1 - Polymer dispersed liquid crystal lenz - Google Patents

Abstract

The present invention relates to a polymer dispersed liquid crystal lens, and more particularly, to a polymer dispersed liquid crystal lens implementing a high-speed switching function and an auto shading function by using a photo-polymerization method using heat curing or light curing.
The polymer dispersed liquid crystal lens according to the invention is advantageous for mass production because the production cost is low. Unlike the conventional production method of LCD, alignment process, spacer spreading process, sealant and end sealant manufacturing process and polarizing film adhering process are not necessary, which makes it possible to simplify the manufacturing process.
Polymer dispersed liquid crystal lenses using a glass substrate have a high functionality goggles such as an extremely low amount of light and a fast response speed, new active shutter goggles and auto shading sunglasses, Can be developed.
Also, since such a polymer dispersed liquid crystal lens can be produced by various methods such as induction of phase separation using photopolymerization, separation of liquid crystal and polymer through heating, solvent evaporation and emulsification, development of suitable polymer dispersed liquid crystal lens .

Description

POLYMER DISTRIBUTED LIQUID CRYSTAL LENZ}

The present invention relates to a polymer dispersed liquid crystal lens, and more particularly, to a polymer dispersed liquid crystal lens implementing a high-speed switching function and an auto shading function by using a photo-polymerization method using heat curing or light curing.

Polymer dispersed liquid crystal (PDLC) is a device capable of actively controlling transparency and opacity by using an electric field without using a polarizer because a droplet of a liquid droplet having a micro size is dispersed in a polymer matrix.

Problems such as cross talk and motion blur when using an active shutter type goggle such as a three-dimensional display are caused by vomiting and physiological And the like.

Particularly, the goggles which can be applied to the three-dimensional display can be applied to the three-dimensional goggles by using a lens mounted on the goggles at a frequency of 120 Hz in order to request a quick response characteristic. When using a lens having a slow response characteristic, There has been a problem that it is difficult to apply it because it causes the above-described problems.

1 is a schematic diagram showing a configuration and operation principle of a conventional LCD.

1, in order to induce a twisted nematic structure, the rubbing directions of the upper and lower substrates 10 and 20 are arranged to be 90 degrees with respect to each other. When the voltage is not applied, since the arrangement of the molecules of the liquid crystal 30 is determined only by the orientation film of the upper and lower substrates, the structure is tilted 90 degrees continuously from the lower substrate 20 to the upper substrate 10. At this time, the upper and lower polarizing plates 40 and 50 are attached to the outside of the substrate such that their polarization axes are parallel to the alignment direction of the substrate. The light polarized by the linearly polarized light from the upper polarizer 10 is polarized stepwise along the twisted structure of the liquid crystal and polarized parallel to the zero transmission axis of the lower polarizer 20.

At this time, when 3 to 5 V is applied across the upper and lower electrodes, the optical axis of the central portion of the liquid crystal layer 30 becomes parallel to the electric field, and the twisted structure disappears.

Therefore, the direction of polarization of the light does not rotate any more, and the light passing through the liquid crystal molecules is absorbed by the second polarizer 20.

However, in the case of using the nematic liquid crystal without using the polymer dispersed liquid crystal as described above, the use efficiency of the light is low due to the use of the polarizer, the surface orientation is required and the pixel density increases, And the viewing angle is narrowed to about 20 DEG or less.

In order to solve these drawbacks, recently, it is a light scattering mode PDLC in which a liquid crystal is dispersed in a polymer as described above.

However, a liquid crystal lens which can be used for three-dimensional goggles or a sunglass which can control the light transmission efficiency has not yet been developed even though the PDLC is used.

Patent No. 10-257894 (polymer liquid crystal complex)

Disclosure of the Invention The present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a polymer liquid crystal composite capable of having a high-speed switching function while simplifying a manufacturing process as compared with liquid crystal.

The present invention relates to an ITO vacuum-deposited glass comprising (+) electrode and (-) electrode respectively up and down; And a polymer dispersed liquid crystal including 55 to 70% by weight of a liquid crystal and 30 to 45% by weight of a polymer matrix between the glass.

The polymer matrix is prepared by using EHA (2-ethylhexyl acrylate) or BDVE (butanediol vinyl ether) as a monomer, TMPT (trimethylolpropane trimethacrylate) as a cross linker, 2- 2-methylpropiophenone is used as the liquid crystal, and the liquid crystal is selected from the group consisting of n-pentylcyanobiphenyl, n-heptylcyanobiphenyl, n-heptylcyanobiphenyl, an eutectic mixture of n-octyloxycyanobiphenyl and n-pentylcyanoterphenyl, and may be a mixture of the polymer and the liquid crystal, followed by UV curing.

The polymer matrix includes a mixture of tetrafunctional allylether and trifunctional monomer as a prepolymer, benzo-phenone as a photoinitiator, and the liquid crystal is n-pentyl The process of n-pentylcyanobiphenyl, n-heptylcyanobiphenyl, n-octyloxycyanobiphenyl, and n-pentylcyanoterphenyl, eutectic mixture, and the liquid crystal and the prepolymer may be mixed and UV-cured.

The polymer matrix was prepared by using diglycidyl ether as a prepolymer and Methyl-5-norbornene-2,3-dicarboxylic anhydride (MNA) as a curing agent. 2,4,6-tirs (dimethylaminomethyl) -phenol (DMP-30)) was used as the initiator, and the liquid crystal was n-pentyl cyanobiphenyl ( is an eutectic mixture of n-pentylcyanobiphenyl, n-heptylcyanobiphenyl, n-octyloxycyanobiphenyl and n-pentylcyanoterphenyl, The liquid crystal and the polymer may be mixed and then heated to be phase-separated.

The polymer dispersed liquid crystal lens according to the present invention is advantageous for mass production because the production cost is low. Unlike the conventional production method of LCD, alignment process, spacer spreading process, sealant and end sealant manufacturing process and polarizing film adhering process are not necessary, which makes it possible to simplify the manufacturing process.

Polymer dispersed liquid crystal lenses using a glass substrate have a high functionality goggles such as an extremely low amount of light and a fast response speed, new active shutter goggles and auto shading sunglasses, Can be developed.

Also, since such a polymer dispersed liquid crystal lens can be produced by various methods such as induction of phase separation using photopolymerization, separation of liquid crystal and polymer through heating, solvent evaporation and emulsification, development of suitable polymer dispersed liquid crystal lens .

1 is a schematic view showing transmission characteristics of a twisted nematic lens in an LCD lens.
2 is a diagram showing the phase balance of a liquid crystal and a polymer matrix
3 is a view showing the formula of the liquid crystal used in the polymer dispersed liquid crystal lens according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the following embodiments are provided so that those skilled in the art will be able to fully understand the present invention, and that various modifications may be made without departing from the scope of the present invention. It is not. Wherein like reference numerals refer to like elements throughout.

The permittivity in an electric field can be easily obtained by measuring the capacitance of a planar capacitor filled with a specific material. Mixed liquid crystal materials used in displays contain a large number of compounds having large dipole moments, so that the effect of electron polarization is negligibly small in reality. In this liquid crystal, there is a difference between ε // and ε 되며, and a large value of ε is directly related to the threshold voltage of the liquid crystal. Although some values are negative, most of the nematic liquid crystals have positive Δε values.

The liquid crystal shows anisotropy of refractive index, that is, birefringence, since it optically shows a single-axis crystal. Single axis crystals have two refractive indices, ne and no. no is the refractive index for an ordinary ray whose electrical vector is oscillating perpendicular to the plane on which the optical axis lies and ne is the ratio of the oscillation of the electrical vector to the extraordinary ray parallel to the plane on which the optical axis lies. The birefringence DELTA n corresponds to the difference between the refractive indices ne and no.

Solids have regular order in all directions, but liquids have no regularity. Therefore, it can be seen that the liquid crystal, which is the intermediate phase, has a tendency to align molecules in a uniform direction like a solid. When the light passes through, the difference in speed between the light of the component arranged in one direction and the light of the component in the vertical direction is expressed by the difference (Δn) between the refractive indices of the respective components. This material with a difference in refractive index is called birefringent material, and liquid crystal is birefringent material having optical anisotropy. The direction in which the two refractive indices coincide is called the optics axis. In the case of a liquid crystal, there is one optical axis.

When two polarizations in different states pass through a birefringent material having a thickness d, a phase difference? Occurs.

Where Δn is the difference between Nx and Ny and corresponds to ne and no in the liquid crystal (Δ

n = ne-no). Therefore,? Is expressed by Equation (1).

Where Δn is the difference between Nx and Ny and corresponds to ne and no in the liquid crystal. (? N = ne-no). In particular, Δn · d is the retardation delay, and in this system, the phase difference delay is calculated in this system.

If the liquid crystal polymer has already ordered the polymer on the liquid crystal, which is a fluid phase, solid state of the liquid crystal polymer having a much higher orientation order than that of the general crystalline polymer can be obtained.

The photopolymerization of the polymer and the liquid crystal as described above will be described in detail as follows.

Light is classified according to wavelength by being perceived by human eyes, and has both particle and wave. The radiation of a molecule is determined by the frequency (v), wavelength (λ) and energy (E) of the molecule.

UV lamps are the most commonly used equipment when dealing with photocuring. There are many types of lamps, depending on the emission wavelength, the intensity of the emitted light, and the temperature at which they operate. Usually, high-pressure mercury lamps are used. The emission spectrum of such a lamp overlaps with the absorption spectrum of the photoinitiator, so that the photoinitiation can be effectively performed.

The polymer used in the UV curing process according to the present invention may be prepared by using EHA (2-ethylhexyl acrylate) or BDVE (butanediol vinyl ether) as a monomer, TMPT (trimethylolpropane trimethacrylate) as a cross linker, (2-hydroxy-2-methylpropiophenone) is used as a photoinitiator, and the liquid crystal is selected from n-pentylcyanobiphenyl, n-heptyl Is an eutectic mixture of n-heptylcyanobiphenyl, n-octyloxycyanobiphenyl and n-pentylcyanoterphenyl. The polymer is mixed with the liquid crystal to form a UV It is preferable to use a cured product.

Another polymer that can be used as a photo-curing agent is a mixture of tetrafunctional allylether and trifunctional monomer as a prepolymer, benzo-phenon as a photoinitiator, , The liquid crystal is selected from the group consisting of n-pentylcyanobiphenyl, n-heptylcyanobiphenyl, n-octyloxycyanobiphenyl and n-pentylcyanophenyl ( n-pentylcyanoterphenyl), and it is preferable that the liquid crystal and the prepolymer are mixed and UV-cured.

In the UV irradiation described above, the UV intensity is preferably irradiated at an irradiation range of 200 to 1000 mW / cm 2, and the central wavelength of UV is preferably irradiated at a range of 300 to 400 nm.

As another method of producing a polymer dispersed liquid crystal, a process of producing a polymer dispersed liquid crystal lens using heat is described in detail. In this case, an epoxy-based polymer dispersion liquid droplet is formed. Thermal induced phase separation (TIPS) using heat-induced phase separation is different in that it uses heat-induced phase separation. In the case of a polymer dispersed liquid crystal using heat-induced phase separation, diglycidyl ether is used as a prepolymer. Methyl-5-norbornene-2,3-dicarboxylic anhydride (MNA) is used as the curing agent, 2,4,6-tris Phenol (2,4,6-tirs (dimethylaminomethyl) -phenol) (DMP-30)) is preferably used.

In the case of using heat-induced phase separation, similarly to the case of photopolymerization, firstly, the liquid crystal is uniformly dispersed in the polymer matrix and the ITO (indium tin oxide) is vacuum-deposited on the glass substrate. The pouring process is the same as in the case of photopolymerization.

However, there is only difference in using heat as a method of starting polymerization in this state.

The size of the droplet is determined by the material constants including cooling rate, viscosity, and chemical potential.

In addition to the above-described methods, methods such as solvent induced phase separation (SIPS) and emulsification may also be used.

In the case of the phase separation method using a solvent, when a liquid crystal or a thermoplastic plastic dissolves in a specific solvent, the two substances are dissolved in a solvent to obtain a homogeneous mixed solution, and a liquid crystal is formed by a method of evaporating the solvent. The size of the droplet showing the orientation characteristics according to the application of the electric field is determined by the evaporation rate of the solvent.

The emulsification method is a method in which a liquid crystal is mixed with a water-soluble polymer solution such as PVA, and then an emulsion is formed using a blender or a colloidal mill. The thus formed tanning agent is coated on a substrate on which ITO is vacuum-deposited and then dried to form a thin film.

The method of producing polymer dispersed liquid crystal using photopolymerization is such that the size, shape, and dispersion state of liquid droplets constituting the liquid crystal are more uniform than those of other methods, and due to the property of obtaining such a uniform lens, And the transparency becomes uniform.

The polymer dispersed liquid crystal lens prepared by photopolymerization has a wide selection of monomer and oligomer prepolymer and is advantageous in manufacturing a polymer dispersed liquid crystal lens having various morphologies.

2 is a diagram showing the phase balance of a liquid crystal and a polymer matrix

Referring to FIG. 2, as the content of the liquid crystal is small and the temperature is high, the liquid crystal and the polymer have high compatibility with each other. Also, it can be seen that as the content of liquid crystal increases, it exhibits a nematic property. And between the regions of the liquid crystals φ1 and φ2, nematic and isotropic phases coexist.

It is preferable that the polymer dispersed liquid crystal lens according to the present invention has a liquid crystal having a small size and a plurality of liquid crystals arranged on the polymer matrix in order to have a high response characteristic according to voltage application.

When the molecular weight of the polymer matrix increases due to the photopolymerization reaction, the liquid crystal starts to elute in the polymer matrix, and phase separation of the liquid crystal and the polymer appears. The reaction of the liquid crystal in the polymer due to the phase separation of the liquid crystal and the polymer as described above is a main factor determining the shape and structure of the droplet in the liquid crystal inside the polymer dispersed liquid crystal lens.

Referring to FIG. 2, the weight ratio of the polymer to the liquid crystal is preferably 55 to 70% by weight.

If the weight ratio of the liquid crystal is less than 55% by weight, the number of droplets to be generated in the phase separation process is too small to lower the transmittance of the polymer dispersed liquid crystal lens.

If the weight ratio of the liquid crystal is 70% by weight or more, it is difficult to uniformly disperse the liquid droplets eluted from the liquid crystal due to the small amount of the polymer in the liquid state. If the liquid droplets are not uniformly dispersed in the polymer, It is difficult to show transparency when a voltage of 1 to 10 V is applied.

3 is a view showing the formula of the liquid crystal used in the polymer dispersed liquid crystal lens according to the present invention.

As shown in FIG. 3, the liquid crystal dispersed in the polymer is n-pentylcyanobiphenyl, n-heptylcyanobiphenyl, n-octyloxycyanobiphenyl, ) And an eutectic mixture of n-pentylcyanoterphenyl is preferably used.

The liquid crystal dispersed in the above-mentioned polymer is collectively referred to as "E7" manufactured by Merck. When selecting the liquid crystal, it is preferable to select a liquid crystal having a refractive index similar to the refractive index in the polymer.

It is the same principle as a general LCD that a light transmission characteristic is exhibited when the refractive index in a polymer matches the refractive index of a liquid crystal.

The polymer dispersed liquid crystal using the flexible substrate during the ON time given as the control signal at the driving frequency of 120 Hz becomes a state where power is applied for 200 μs and the light transmittance is close to 100% A voltage can not be applied to the polymer dispersed liquid crystal lens using the flexible substrate.

In addition, since the polymer dispersed liquid crystal lens using the flexible substrate according to the present invention is excellent in light transmission efficiency as compared with the conventional LCD, it has an advantage that it can be used for sunglasses having an auto shading function.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, This is possible.

10: upper substrate 20: lower substrate
25: polymer matrix 30: liquid crystal

Claims (4)

delete delete Glass in which ITO is vacuum deposited on the top and the bottom, respectively including (+) electrode and (-) electrode; And
A polymer dispersed liquid crystal located between the glasses and having a weight ratio of 55 to 70% by weight of the liquid crystal and 30 to 45% by weight of the polymer matrix; ≪ / RTI >
The polymer matrix may be prepared by using a mixture of tetrafunctional allylether and trifunctional monomer as a prepolymer,
Using benzo-phenon as a photoinitiator,
The liquid crystal is preferably selected from the group consisting of n-pentylcyanobiphenyl, n-heptylcyanobiphenyl, n-octyloxycyanobiphenyl and n-pentylcyanophenyl (n < / RTI > pentylcyanoterphenyl,
Wherein the liquid crystal and the prepolymer are mixed and UV-cured. Glass in which ITO is vacuum deposited on the top and the bottom, respectively including (+) electrode and (-) electrode; And
A polymer dispersed liquid crystal located between the glasses and having a weight ratio of 55 to 70% by weight of the liquid crystal and 30 to 45% by weight of the polymer matrix; ≪ / RTI >
The polymer matrix was prepared by using diglycidyl ether as a prepolymer and Methyl-5-norbornene-2,3-dicarboxylic anhydride (MNA) as a curing agent. 2,4,6-tirs (dimethylaminomethyl) -phenol (DMP-30)) was used as the initiator,
The liquid crystal is preferably selected from the group consisting of n-pentylcyanobiphenyl, n-heptylcyanobiphenyl, n-octyloxycyanobiphenyl and n-pentylcyanophenyl (n < / RTI > pentylcyanoterphenyl,
Wherein the liquid crystal and the polymer are mixed and then heated to be phase-separated.

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