KR19990030477A - Polymer combination liquid crystal for liquid crystal display - Google Patents

Abstract

PURPOSE: To provide a polymer-combined liquid crystal for liquid crystal display device using a ferroelectric and anti-ferroelectric liquid crystal, while reducing the mixing ratio of the liquid crystal to the polymer, the response speed is fast, optically stable and excellent contrast.

Composition: A polymer liquid crystal for a liquid crystal display device having a ferroelectric liquid crystal and an antiferroelectric liquid crystal of 40 wt% or less and a polymer 60 wt% or more. The polymer is obtained by polymerizing a urethane acrylate oligomer and an acrylate or methacrylate monomer.

Effect: The use of ferroelectric liquid crystal and semiferroelectric liquid crystal with macroscopic spontaneous polarization improves the selection characteristics to transmit or block light, resulting in improved contrast at on / off, high response speed, and high transmittance and wide viewing angle. . The use of a small amount of liquid crystal can lower the manufacturing cost and suppress aging.

Description

Polymer combination liquid crystal for liquid crystal display

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to Polymer Assemble Liquid Crystal (PALC) for liquid crystal display devices. In particular, the liquid crystal display has a high response speed, optical stability, and contrast, while reducing the mixing ratio of liquid crystal to polymer using ferroelectric and antiferroelectric liquid crystals Relates to an excellent polymer combination liquid crystal.

A liquid crystal display (LCD) is a display device that injects a liquid crystal material between two glass substrates facing each other, and applies an external voltage to display an image by using an electro-optic characteristic of the liquid crystal. Twisted nematic (TN), super twisted nematic (STN), electrically controlledlable birefringence (ECB) LCD, thin film transistor (TFT) LCD, and polymer dispersed using scattering mode ) LCD, etc.

In the conventional liquid crystal display device using such nematic liquid crystals, both TN LCD and STN LCD, which are widely used, use two polarizing plates, so the light loss is high and brightness is a problem. Since it is oriented, it has a disadvantage that the viewing angle is narrow.

Meanwhile, a liquid crystal display using a polymer dispersed liquid crystal (PDLC), in which fine liquid crystal droplets are formed in a matrix of a polymer material to display information in the form of scattering or absorbing light in response to a voltage applied from the outside. Unlike other liquid crystal displays using nematic liquid crystals, the polarizing plate is not used, and the luminance is good, and the rubbing process for aligning the liquid crystal is omitted, and thus the manufacturing process is simple.

However, conventional polymer dispersed liquid crystals have low contrast, which makes it difficult to implement letters, and when the liquid crystal content is low, the liquid crystal properties are poor and the characteristics of the display device are deteriorated. Therefore, since the liquid crystal content is very large and is easily aging by ultraviolet (UV), it has a fatal weakness as a display device, and thus its use has been limited.

In addition, in the conventional PDLC, the nematic liquid crystal is arranged according to the direction of the voltage to transmit light when a voltage is applied from the outside using the nematic liquid crystal, but the molecules are arranged regularly in one direction due to the characteristics of the nematic liquid crystal. There is a problem that the effect of blocking the light falls because it is not.

The present invention is to solve the problems of the prior art described above, by using a ferroelectric and antiferroelectric liquid crystal to reduce the amount of liquid crystals, while reducing the mixing ratio for the polymer, the response speed is fast, optically stable and It is an object of the present invention to provide a polymer combination liquid crystal (PALC) for a liquid crystal display device, in particular, which can improve contrast.

In order to achieve the above object, the present invention provides a polymer-combined liquid crystal obtained by mixing a ferroelectric and antiferroelectric liquid crystal and a polymer having a permanent dipole and having spontaneous polarization macroscopically.

The ferroelectric liquid crystal and the antiferroelectric liquid crystal have a fast response speed and stable molecular arrangement, and are mixed at 40 wt% or less with respect to the total amount of the polymer combined liquid crystal, and thus the mixing ratio of the polymer may be 60 wt% or more.

In this case, the ferroelectric liquid crystal and the antiferroelectric liquid crystal should be well blended at a predetermined ratio so that crystals do not come out. Preferably, the ferroelectric liquid crystal: the antiferroelectric liquid crystal is used in a ratio of 15 to 30%: 5 to 10% with respect to the whole.

Ferroelectric liquid crystal

,

,

(Wherein R is an alkyl group of C ₈ to C ₁₂ )

or

(Wherein R ₁ is an alkyl group of C ₇ to C ₁₀ )

Ferroelectric liquid crystals, such as these, can be used.

With antiferroelectric liquid crystal

,

,

(Wherein R ₁ is an alkyl group of C ₇ to C ₁₀ )

You can choose from.

The polymer is a urethane acrylate-based oligomer (such as CN972 (product of Sartomer®, Japan), EB4827 (product of RDCURE, Japan), Aronix (Japan, name of Dong-A Synthetic Chemical). oligomers) and acrylates or methacrylates, such as ethylhexyl acrylate (EHA), hexanediol dimethacrylate (HDDMA), trimethylolpropane triacrylate (TMPTA), dipentaerythrotol pentaacrylate (DPETA), and the like. It is obtained by polymerizing a monomer of the (methacrylate) series.

In addition, the liquid crystal of the present invention may further add a dye to the ferroelectric and antiferroelectric liquid crystals. At this time, the dye is added in a small amount so that it can be dissolved in the liquid crystal within 40 wt% of the mixing ratio of the ferroelectric and anti-ferroelectric liquid crystal.

As the dye, D5, D35 (product name of BDH company, UK), L-dye B (product name of Roche-Suisse, Switzerland) or G209, G168, G165, G224, G232 (product name of Japan Photochromic Research Institute) are conventionally used in this field. The dyes used in the art can be used.

In the display device using the polymer-combined liquid crystal of the present invention, when the electric field is turned off, the refractive index of the liquid crystal and the polymer are inconsistent with each other to scatter light, and when the electric field is applied, the liquid crystal and the polymer have the same refractive index. do.

In addition, when the dye is added, the color of the dye at the time of light scattering is shown by the guest-host effect, and when the refractive index is the same, the transparent state is shown.

Accordingly, the polymer-combined liquid crystal of the present invention has a faster response speed and improved selectivity for transmitting or blocking light due to the ferroelectric liquid crystal and the antiferroelectric liquid crystal having macroscopic spontaneous polarization, thereby improving contrast on / off, and Maintaining high transmittance and wide viewing angle improves overall optical properties.

In addition, since the polymer combination liquid crystal of the present invention can adjust the path of light even in a small amount for the same reason as described above, it can be manufactured as a display device even if the mixing ratio of the liquid crystal is reduced, and as a result, the manufacturing cost can be reduced and aging can be suppressed. .

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments in which the present invention can be specifically realized.

Example 1

30 wt% of ferroelectric liquid crystal (Wherein R is an alkyl group of C ₈ to C ₁₂ ) and 10 wt% of the antiferroelectric liquid crystal After heating, the mixture is heated in an isotropic liquid crystal state and mixed, and then cooled slowly to room temperature so that crystals do not come out.

The liquid crystal thus mixed was mixed with urethane acrylate and trimethylolpropane triacrylate (TMPTA), and 40 wt% of ferroelectric liquid crystal and antiferroelectric liquid crystal, and urethane acrylate and trimethylolpropane triacrylate (TMPTA) were polymerized. The polymer combination liquid crystal of this invention which becomes 60 weight% of polymers was obtained.

Example 2

Prepared by the same method using the same material as in Example 1, except that the mixing ratio of the liquid crystal is 40 wt% to 20 wt%, the ferroelectric liquid crystal and antiferroelectric liquid crystal is maintained at a ratio of 3: 1 The polymer-combined liquid crystal of the present invention was obtained, which is 80 wt% of a polymer obtained by polymerizing 20 wt% of a liquid crystal and an antiferroelectric liquid crystal and a urethane acrylate and trimethylolpropane triacrylate (TMPTA).

Example 3

30 wt% of ferroelectric liquid crystal (Wherein R is an alkyl group of C ₈ to C ₁₂ ) and 10 wt% of the antiferroelectric liquid crystal After heating, the mixture is heated in an isotropic liquid crystal state and mixed, and then cooled slowly to room temperature so that crystals do not come out.

The liquid crystals thus mixed are mixed together with urethane acrylate and ethylhexyl acrylate (EHA) to obtain 40 wt% of ferroelectric liquid crystal and antiferroelectric liquid crystal, and 60 wt% of polymerized urethane acrylate and ethylhexyl acrylate (EHA). The polymer combined liquid crystal of the present invention was obtained.

Example 4

Prepared by the same method using the same material as in Example 3, except that the mixing ratio of the liquid crystal is 40 wt% to 20 wt%, the ferroelectric liquid crystal and antiferroelectric liquid crystal is maintained at a ratio of 3: 1 The polymer-combined liquid crystal of the present invention was obtained, which is 80 wt% of a polymer obtained by polymerizing 20 wt% of a liquid crystal and an antiferroelectric liquid crystal and a urethane acrylate and an ethexyl acrylate (EHA).

Example 5

30 wt% of ferroelectric liquid crystal (Wherein R ₁ is a C ₇ -C ₁₀ alkyl group) and 10 wt% of the antiferroelectric liquid crystal (Wherein R ₁ is a C ₇ -C ₁₀ alkyl group), the mixture is warmed and mixed in an isotropic liquid crystal state and then cooled slowly to room temperature so that crystals do not come out.

The mixed liquid crystals were mixed with urethane acrylate and hexanediol dimethacrylate (HDDMA), and 40 wt% of ferroelectric liquid crystal and antiferroelectric liquid crystal, polymerized with urethane acrylate and hexanediol dimethacrylate (HDDMA) 60 The polymer combined liquid crystal of the present invention at wt% was obtained.

Example 6

Prepared by the same method using the same material as in Example 5, except that the mixing ratio of the liquid crystal is 40 wt% to 20 wt%, the ferroelectric liquid crystal and antiferroelectric liquid crystal is maintained at a ratio of 3: 1 The polymer-combined liquid crystal of the present invention was obtained, which is 80 wt% of a polymer obtained by polymerizing 20 wt% of a liquid crystal and an antiferroelectric liquid crystal and a urethane acrylate and hexanediol dimethacrylate (HDDMA).

Example 7

The ferroelectric and antiferroelectric liquid crystal materials of Example 1 are heated and mixed in an isotropic liquid crystal state and then cooled slowly to room temperature so that crystals do not come out. The D5 (trade name of BDH Co., Ltd., UK) dyes are mixed in small amounts so that they can be dissolved in the liquid crystal so that the mixing ratio of liquid crystal and dye is 40%. The liquid crystal thus mixed was mixed with urethane acrylate and trimethylolpropane triacrylate (TMPTA) to form 40 wt% of ferroelectric liquid crystal, antiferroelectric liquid crystal and dye, and urethane acrylate and trimethylolpropane triacrylate (TMPTA). The polymer combined liquid crystal of the present invention which is 60 wt% of a polymerized polymer was obtained.

The dye dissolved in the liquid crystal displays color by a guest-host effect that is oriented along the liquid crystal when voltage is applied.

Example 8

The ferroelectric and antiferroelectric liquid crystal materials of Example 3 are heated and mixed in an isotropic liquid crystal state and then slowly cooled to room temperature so that crystals do not come out. Here, L-dye B (Switzerland, Roh-Shoo product name) dye is mixed in small amounts so that the liquid crystal and the dye mixture ratio is 40%, and melted well. The mixed liquid crystals were mixed with urethane acrylate and ethylhexyl acrylate (EHA) to obtain 40 wt% of ferroelectric liquid crystal, antiferroelectric liquid crystal and dye, and 60 wt% of polymer polymerized with urethane acrylate and ethylhexyl acrylate (EHA). The polymer combined liquid crystal of the present invention was obtained.

Example 9

The ferroelectric and antiferroelectric liquid crystal materials of Example 5 are heated and mixed in an isotropic liquid crystal state, and then cooled slowly to room temperature so that crystals do not come out. In addition, the mixture of G209 (Japan, Japan Photosensitive and Dyestuffs) dyes is mixed in small amounts so that the liquid crystal and dye mix ratio is 40%. The liquid crystal thus mixed was mixed with urethane acrylate and hexanediol dimethacrylate (HDDMA), and 40 wt% of ferroelectric liquid crystal, antiferroelectric liquid crystal and dye, and urethane acrylate and hexanediol dimethacrylate (HDDMA) were polymerized. The polymer combination liquid crystal of this invention which becomes 60 weight% of polymers was obtained.

Comparative Example (Prior Art)

In order to compare with the polymer combination liquid crystal of the present invention, a nematic liquid crystal 60 wt% was mixed with 40 wt% of a commercially available polymer, and ultraviolet light was exposed to obtain a conventional polymer dispersed liquid crystal (PDLC).

Example 10

The polymer combination liquid crystal of the present invention is injected between a pair of substrates on which a transparent electrode is formed, and then sealed to prepare a liquid crystal cell.

The light source was placed at a distance of 20 to 30 cm away from the liquid crystal cell and tested by varying the driving voltage. Table 1 shows the transmittance, response speed, contrast, and viewing angle measurement data measured at the driving voltage of 20v.

Table 1

Item unit Example 1 Example 2 Example 3 Example 4 Example 5 Response speed Ton msec 39.8 68.3 40.8 62.4 39.0 Toff 26.0 22.3 26.0 23.2 25.8 Contrast Ratio 100: 1 90: 1 100: 1 95: 1 100: 1 Light transmittance % 89.00 88.27 88.82 86.24 89.00 Viewing angle Degree ± 50 ± 45 ± 50 ± 45 ± 50

Item unit Example 6 Example 7 Example 8 Example 9 Comparative example Response speed Ton msec 39.4 44.2 52.4 50.2 139.8 Toff 26.0 23.4 24.7 25.8 125.9 Contrast Ratio 90: 1 100: 1 100: 1 95: 1 10: 1 Light transmittance % 86.18 89.00 88.36 87.47 70.0 Viewing angle Degree ± 50 ± 50 ± 50 ± 45 ± 40

As shown in the table, the polymer-combined liquid crystal according to the present invention has a transmittance of 86 to 89%, a response speed of 100 msec or less, a contrast of 100: 1, and a maximum field of view of ± 50 °. Can be.

As can be seen from the embodiments and comparative examples described above, the polymer-combined liquid crystal for liquid crystal display device according to the present invention substantially solves the problems of the prior art.

In other words, according to the present invention, ferroelectric liquid crystals having macroscopic spontaneous polarization and antiferroelectric liquid crystals have improved selection characteristics for transmitting or blocking light, thereby improving contrast on and off, fast response speed, and high transmittance and wide range. Since the viewing angle is maintained, the optical characteristic is improved as a whole.

In addition, according to the present invention, since the light path can be adjusted even with a small amount of liquid crystal, the display device can be manufactured even if the mixing ratio of the liquid crystal is reduced. As a result, the manufacturing cost can be lowered and aging can be suppressed.

Therefore, the polymer combination liquid crystal of the present invention can realize not only the optical shutter function but also the realization of characters.

Claims (5)

A polymer combination liquid crystal for a liquid crystal display device having a ferroelectric liquid crystal and an antiferroelectric liquid crystal of 40 wt% or less and a polymer 60 wt% or more. The liquid crystal display of claim 1, wherein the mixing ratio of the polymer is 60 to 80 wt%. The liquid crystal display liquid crystal display device according to claim 1 or 2, wherein a mixing ratio of the ferroelectric liquid crystal is 15 to 30 wt%. The polymer combination liquid crystal of claim 1, wherein the polymer is obtained by polymerizing a urethane acrylate oligomer and an acrylate or methacrylate monomer. 2. The liquid crystal display of claim 1, wherein a dye is added to the ferroelectric liquid crystal and the antiferroelectric liquid crystal so that the total addition ratio thereof is 40 wt% or less.