LIQUID CRYSTAL CELL

Abstract

The present application relates to a liquid crystal cell and a use of the liquid crystal cell. The present application can provide a liquid crystal cell which is capable of switching between a transparent mode and a scattering mode by using a non-ionic compound as a liquid crystal additive for realizing the EHDI characteristics and has excellent performance such as a driving voltage characteristic, a haze characteristic and reliability by securing solubility of the additive for liquid crystals. Such a liquid crystal cell can be applied to various light modulation devices such as a smart window, a window protective film, a flexible display device, a light shielding plate for transparent display, an active retarder for 3D image display, or a viewing angle adjusting film.

Claims

1. A liquid crystal cell switching between a transparent mode and a scattering mode by applying external energy and having a liquid crystal layer comprising a liquid crystal compound and a non-ionic compound.

2. The liquid crystal cell according to claim 1, wherein said liquid crystal compound has a negative dielectric anisotropy.

3. The liquid crystal cell according to claim 1, wherein said non-ionic compound comprises a high dielectric constant material having a dielectric constant () of 3 or more.

4. The liquid crystal cell according to claim 3, wherein said high dielectric constant material comprises one or more selected from the group consisting of alkylene carbonate compounds, lactone compounds, dioxilane compounds, sulfolane compounds and alkyl aniline compounds.

5. The liquid crystal cell according to claim 3, wherein said liquid crystal cell satisfies Equation 1 below:
y=110.sup.7x+410.sup.71.010.sup.5 [Equation 1] wherein, y represents a horizontal conductivity (.sub.//) (unit: S/m) of the liquid crystal layer and x represents a dielectric constant () of the non-ionic compound (provided that the ratio of the non-ionic compound in the liquid crystal layer is 10% by weight).

6. The liquid crystal cell according to claim 1, wherein said non-ionic compound comprises a reactive mesogen.

7. The liquid crystal cell according to claim 6, wherein said reactive mesogen comprises a compound represented by Formulas 2 to 5 below: ##STR00015## wherein, P.sub.1 to P.sub.6 represent independently of each other a (meth)acrylate group, a carboxyl group, a hydroxy group, a vinyl group, an epoxy group or a nitro group, X.sub.1 to X.sub.5 represent independently of each other a single bond, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms or a substituted or unsubstituted alkoxy group having 1 to 10 carbon atoms, L.sub.2 to L.sub.7 represent independently of each other a single bond, a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenylene group having 1 to 10 carbon atoms, a substituted or unsubstituted alkenylene group having 1 to 10 carbon atoms, a substituted or unsubstituted alkoxylene group having 1 to 10 carbon atoms, O or COO, A.sub.5 to A.sub.8 represent independently of each other hydrogen, halogen, a cyano group, a substituted or unsubstituted alkyl group having 1 to 3 carbon atoms or a substituted or unsubstituted alkoxy group having 1 to 2 carbon atoms, Y.sub.1 to Y.sub.2 represent independently of each other hydrogen, halogen, a cyano group, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or an alkoxy group having 1 to 10 carbon atoms unsubstituted or substituted with at least one substituent selected from the group consisting of a cyano group, halogen and an alkenyl group.

8. The liquid crystal cell according to claim 6, wherein said liquid crystal layer has a horizontal conductivity (.sub.//) or a vertical conductivity (.sub.) of 1.010.sup.4 S/cm or more (said horizontal conductivity or vertical conductivity means a conductivity value obtained by converting the conductivity measured under an application condition of a voltage of 0.5 V and a frequency of 60 Hz at room temperature based on a liquid crystal cell having an area of 1 cm.sup.2 and an interval of 1 cm).

9. The liquid crystal cell according to claim 1, wherein said liquid crystal layer is not recrystallized at room temperature.

10. The liquid crystal cell according to claim 1, wherein said liquid crystal layer further comprises an anisotropic dye.

11. The liquid crystal cell according to claim 1, wherein said liquid crystal layer is formed to be capable of switching between a transparent mode having a haze of less than 10% and a scattering mode having a haze of 10% or more.

12. The liquid crystal cell according to claim 1, wherein said liquid crystal layer is formed to be in a transparent mode in a state in which no external energy is applied and to be capable of switching to a scattering mode when external energy is applied.

13. The liquid crystal cell according to claim 1, wherein said liquid crystal compound exists in a vertically aligned state in a state in which no external energy is applied.

14. The liquid crystal cell according to claim 1, further comprising two substrates disposed opposite to both sides of said liquid crystal layer.

15. The liquid crystal cell according to claim 1, further comprising two vertical alignment films disposed opposite to both sides of said liquid crystal layer.

16. The liquid crystal cell according to claim 1, further comprising two electrode layers disposed on both sides of said liquid crystal layer.

17. A smart window comprising the liquid crystal cell of claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0099] FIG. 1 illustratively shows a driving method of the liquid crystal cell of the present application.

[0100] FIGS. 2 to 4 illustratively show the liquid crystal cell of the present application.

[0101] FIG. 5 shows the relationship between the dielectric constant of the liquid crystal additive of Examples 1 to 3 and the horizontal conductivity of the liquid crystal layer.

[0102] FIG. 6 shows the results evaluating the haze according to the voltages of Examples 1 to 3.

[0103] FIG. 7 shows the results evaluating the haze according to the voltages of Comparative Examples 1 and 2.

[0104] FIG. 8 shows the results evaluating the haze according to the voltages of Examples 5 and 9.

MODE FOR INVENTION

[0105] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the scope of the present application is not limited by the details set forth below.

EVALUATION EXAMPLE 1

Evaluation of Solubility Characteristics

[0106] (1) The bottles of the liquid crystal compositions prepared in Examples and Comparative Examples were left at room temperature to observe recrystallization. When crystals adhered to the bottle wall are observed with the naked eye, it means that the storage characteristics at room temperature of the liquid crystal composition are not secured.

[0107] (2) The liquid crystal cells prepared in Examples and Comparative Examples were stored at room temperature and 20 C., respectively, to observe recrystallization. They were observed daily at room temperature for at least one month and observed at 20 C. after standing for at least 5 days. When crystals of the liquid crystal cell are observed with the naked eye, it means that the solubility characteristics are not secured.

[0108] <Evaluation Criteria for Solubility Characteristics>

[0109] O: Recrystallization during the above observations is not observed with the naked eye

[0110] X: Recrystallization is observed with naked eyes even in any one of the above observations

EVALUATION EXAMPLE 2

Evaluation of Conductivity Characteristics

[0111] For the liquid crystal cells prepared in Examples and comparative Examples, the conductivity at room temperature was measured using a LCR meter (E4980A, Agilent) under a condition at a measuring frequency of 60 Hz and a measuring voltage of 0.5 V (unit: S/m). The horizontal conductivity (.sub.//) was measured by applying a vertical voltage, that is a voltage in the thickness direction of the liquid crystal layer, to the vertically aligned liquid crystal layer, and the vertical conductivity (.sub.) was measured by applying also the vertical voltage to the horizontally aligned liquid crystal layer. The converted conductivity (unit: S/cm) can be obtained by converting the measured conductivity based on an area of 1 cm.sup.2 and an interval of 1 cm.

EVALUATION EXAMPLE 3

Evaluation of Haze and Transmittance

[0112] For the liquid crystal cells prepared in Examples and Comparative Examples, while driving them by connecting an AC power source (frequency: 60 Hz) to the upper and lower ITO transparent electrode layers and applying the vertical electric field, the haze and transmittance according to voltages were measured using a haze meter, NDH-5000SP by an ASTM method. That is, light is transmitted through a measuring object and entered into an integrating sphere, and in this process, the light is divided into a diffusion light (DT, meaning the sum of all the diffused and emitted light) and a parallel light (PT, meaning the emitted light in the front direction excluding the diffusion light), where these lights are collected in light receiving elements in the integrating sphere, so that the haze may be measured through the collected light. That is, it may be defined that the total transmitted light (TT) by the above procedure is the sum (DT+PT) of the diffusion light (DT) and the parallel light (PT) and the haze is the percentage of the diffusion light to the total transmitted light (Haze (%)=100XDT/TT). In addition, in the following test example, the total transmittance refers to the total transmitted light (TT), and the rectilinear transmittance refers to the parallel light (PT).

EXAMPLE 1

[0113] Preparation of DSM (Dynamic Scattering Mode) Liquid Crystal Composition

[0114] To 10 mL vial, 3.60 g of liquid crystals from HCCH company (HNG726200-100, dielectric anisotropy: 4.0, refractive index anisotropy: 0.225) and 0.40 g of propylene carbonate (dielectric constant at 20 C.: 66.14, Handbook of Organic Solvents R. Lide/CRC Press/Dec. 1, 1994)) (about 10% by weight) as a liquid crystal additive were added and then stirred at 100 C. for 24 hours to prepare a liquid crystal composition.

[0115] Preparation of DSM (Dynamic Scattering Mode) Liquid Crystal Cell

[0116] The liquid crystal composition as prepared above was injected into a glass test cell sequentially forming an ITO transparent electrode layer and a vertical alignment film on the inner side of the cell and having a cell interval of 9 m, using a capillary phenomenon to prepare a liquid crystal cell having an area of 2.2 cm4.0 cm and an interval of 9 m.

EXAMPLE 2

[0117] A liquid crystal cell was prepared by the same method as Example 1, except that in preparing the liquid crystal composition, 0.4 g (about 10% by weight) of sulfolane (dielectric constant at 30 C.: 43.26, Handbook of Organic Solvents (David R. Lide/CRC Press/Dec. 1, 1994)) was used instead of propylene carbonate as a liquid crystal additive.

EXAMPLE 3

[0118] A liquid crystal cell was prepared by the same method as Example 1, except that in preparing the liquid crystal composition, 0.4 g (about 10% by weight) of N,N-diemthylaniline (dielectric constant at 25 C.: 4.90, Handbook of Organic Solvents (David R. Lide/CRC Press/Dec. 1, 1994)) was used instead of propylene carbonate as a liquid crystal additive.

COMPARATIVE EXAMPLE 1

[0119] A liquid crystal cell was prepared by the same method as Example 1, except that in preparing the liquid crystal composition, 0.04 g (about 1% by weight) of CTAB (Hexadecyltrimethylammonium Bromide, TCI) was used instead of propylene carbonate as a liquid crystal additive.

COMPARATIVE EXAMPLE 2

[0120] A liquid crystal cell was prepared by the same method as Example 1, except that in preparing the liquid crystal composition, 0.04 g (about 1% by weight) of CTAC (Hexadecyltrimethylammonium Chloride, TCI) was used instead of propylene carbonate as a liquid crystal additive.

COMPARATIVE EXAMPLE 3

[0121] A liquid crystal cell was prepared by the same method as Example 1, except that in preparing the liquid crystal composition, 0.4 g (about 10% by weight) of CTAB (Hexadecyltrimethylammonium Bromide, TCI) was used instead of propylene carbonate as a liquid crystal additive. In the case of Comparative Example 3, although the content of the liquid crystal additive is the same as that of Example 1, the solubility of CTAB in the liquid crystal medium is not ensured, so that it is not suitable to realize the liquid crystal cell switching between the transparent mode and the scattering mode.

COMPARATIVE EXAMPLE 4

[0122] A liquid crystal cell was prepared by the same method as Example 1, except that in preparing the liquid crystal composition, 0.4 g (about 10% by weight) of CTAC (Hexadecyltrimethylammonium Chloride, TCI) was used instead of propylene carbonate as a liquid crystal additive. Also, in the case of Comparative Example 4, although the content of the liquid crystal additive is the same as that of Example 1, the solubility of CTAC in the liquid crystal medium is not ensured, so that it is not suitable to realize the liquid crystal cell switching between the transparent mode and the scattering mode.

[0123] Evaluation of Horizontal Conductivity

[0124] For the liquid crystal cells prepared in Examples 1 to 3 and Comparative Examples 1 and 2, the horizontal conductivities were measured and the results were shown in Table 1 below. FIG. 5 showed a graph of the horizontal conductivities in the liquid crystal layer to the dielectric constants of the liquid crystal additives of Examples 1 to 3. As shown in FIG. 5, it can be seen that the horizontal conductivity (unit: S/m) of the liquid crystal layer has a linear relationship relative to the dielectric constant of the liquid crystal additive (when the x coordinate is set as the dielectric constant of the liquid crystal additive and the y coordinate is set to the horizontal conductivity of the liquid crystal layer, R.sup.2 in FIG. 5 is a value representing whether x and y values correspond to the equation of y=1E-07x+4E-07 (y=110.sup.7x+410.sup.7), wherein if R.sup.2 is 1, this means to meet 100%, and according to FIG. 5, it can be seen to meet 98.59% with the above equation).

[0125] Haze Evaluation

[0126] For the liquid crystal cells prepared in Examples 1 to 3 and Comparative Examples 1 and 2, hazes were evaluated according to voltages, and then the results were shown in Table 1 and FIGS. 6 (Examples 1 to 2) to 7 (Comparative Examples 1 to 2).

TABLE-US-00001 TABLE 1 Example Comparative Example 1 2 3 1 2 Horizontal Conductivity 7.54 4.46 1.09 3.23 4.56 (.sub.//) (10.sup.6) Haze (%) 30 V 88.6 75.2 66.3 72.0 84.6 50 V 91.9 75.9 68.2 78.3 87.6 60 V 93.6 83.3 74.0 81.2 86.0

EXAMPLE 4

[0127] Preparation of DSM (Dynamic Scattering Mode) Liquid Crystal Composition

[0128] To 10 mL vial, 3.6 g of liquid crystals (HNG726200-100, HCCH company, dielectric anisotropy: 4.0, refractive index anisotropy: 0.225), and 0.40 g of reactive mesogen(RM1) (HCM-008, HCCH company) and 0.04 g of an anisotropic dye (X12, BASF) as additives were added and then stirred at 100 C. for 24 hours to prepare a liquid crystal composition.

[0129] Preparation of DSM (Dynamic Scattering Mode) Liquid Crystal Cell

[0130] After two sheets of PC (polycarbonate) films sequentially forming an ITO (Indium Tin Oxide) transparent electrode layer and a vertical alignment film were disposed apart from each other such that the vertical alignment films faced each other and had an interval of about 9 m, the prepared liquid crystal composition was injected between the apart disposed PC films and the edges were sealed to prepare a liquid crystal cell having an area of 2.2 cm4.0 cm and an interval of 9 m. As the vertical alignment film, one obtained by coating a vertical alignment composition (Nissan 5661) on the ITO transparent electrode layer and baking it at a temperature of 100 C. or more for 5 minutes or more was used.

EXAMPLES 5 TO 8

[0131] A liquid crystal cell was prepared in the same manner as Example 1, except that the kind and content of the liquid crystal additive were adjusted as in Table 2 below.

TABLE-US-00002 TABLE 2 Example 4 5 6 7 8 Liquid HNG726200-100, HCCH, 100% by weight Crystal Additive HCM-008 HCM-009 HCM-020 HCM-021 HCM-064 Type RM1 RM2 RM3 RM4 RM5 Additive 10% by 10% by 10% by 10% by 10% by Content weight weight weight weight weight Dye X12, BASF 1% by weight

##STR00013##

COMPARATIVE EXAMPLES 5 TO 9

[0132] A liquid crystal cell was prepared in the same manner as Example 1, except that the kind and content of the liquid crystal additive were adjusted as in Table 3 below.

TABLE-US-00003 TABLE 3 Comparative Example 5 6 7 8 9 Liquid Crystal HNG726200-100, HCCH, 100% by weight Additive Type CTAB CTAC TPP + I.sub.2 CTC HQBQ Additive 1% by 1% by 2% by 1% by 0.7% by Content weight weight weight weight weight Dye X12, BASF 1% by weigh

##STR00014##

[0133] For Examples 4 to 9 and Comparative Examples 5 to 9, solubility characteristics, conductivity characteristics, haze characteristics and transmittance variable characteristics were evaluated, and then the results were described in Tables 4 to 5 below.

TABLE-US-00004 TABLE 4 Example 4 5 6 7 8 Solubility Characteristic (20 C.)* Measured .sub.// [S/m] 4.66 10.sup.6 3.1 10.sup.6 6.4 10.sup.6 4.8 10.sup.6 3.2 10.sup.6 Converted.sub.//[S/cm] 4.77 10.sup.4 3.17 10.sup.4 6.55 10.sup.4 4.91 10.sup.4 3.27 10.sup.4 Measured.sub.v[S/m] 1.45 10.sup.6 1.3 10.sup.6 3.6 10.sup.6 2.4 10.sup.6 2.1 10.sup.6 Converted.sub.v [S/cm] 1.48 10.sup.4 1.33 10.sup.4 3.68 10.sup.4 2.45 10.sup.4 2.15 10.sup.4 Haze (30 V) (%) 41.7 41.7 92.8 88.6 87.2 Haze (40 V) (%) 88.0 88.0 94.7 94.0 91.6 Haze (60 V) (%) 95.7 95.7 96.0 95.9 94.41 T (0 V 40 V) (%) 39.1 39.5 32.5 40.8 39.3 T (0 V 60 V) (%) 42.8 44.3 38.4 43.5 42.6 Haze (X V): Haze value at X V T (0 V X V): a value obtained by subtracting the transmittance at X V from the transmittance at 0 V *Example 7 has excellent solubility characteristics even at 20 C.

TABLE-US-00005 TABLE 5 Comparative Example 5 6 7 8 9 Solubility Characteristic X X X* X X Measured .sub.// [S/m] 9.7 10.sup.6 4.5 10.sup.6 2.7 10.sup.6 2.5 10.sup.5 2.1 10.sup.6 Converted .sub.//[S/cm] 9.92 10.sup.4 4.60 10.sup.4 2.76 10.sup.4 2.56 10.sup.4 2.15 10.sup.4 Measured .sub.[S/m] 8.1 10.sup.6 3.7 10.sup.6 2.2 10.sup.6 2.2 10.sup.5 1.7 10.sup.6 Converted .sub.[S/cm] 8.28 10.sup.4 3.78 10.sup.4 2.25 10.sup.4 2.25 10.sup.4 1.74 10.sup.4 Haze (30 V) (%) 81.3 66.4 68.3 92.6 27.1 Haze (40 V) (%) 84.8 72.0 81.9 94.9 52.2 Haze (60 V) (%) 88.6 68.1 93.2 95.9 63.0 T (0 V 40 V) (%) 37.2 36.8 33.0 33.9 33.6 T (0 V 60 V) (%) 39.6 39.3 35.2 38.3 35.5 Haze (X V): Haze value at X V T (0 V X V): a value obtained by subtracting the transmittance at X V from the transmittance at 0 V *Comparative Example 3 forms a complex and generates crystals.

EXAMPLE 9

[0134] A liquid crystal cell of Example 9 was prepared in the same manner as Example 4, except that the type and content of the liquid crystal additive were adjusted as in Table 6 below and a filtering process was further performed using a filter having a size of 0.1 m in order to remove the insoluble ionic additive and CTAC.

[0135] In addition, for Example 9, the solubility characteristic, the conductivity characteristic, the haze characteristic and the transmittance variable characteristic were evaluated, and then the results were described as in Table 6 below, compared with those of Example 5. Also, the hazes according to voltages were evaluated for Examples 5 and 9, and the results were shown in FIG. 8.

TABLE-US-00006 TABLE 6 Example 5 Example 9 Liquid Crystal HNG726200-100 Dye X12, BASF 1% by weight RM Additive HCM-009 RM2 HCM-020 RM3 Additive Content 10% by weight 10% by weight Ionic Additive X Filter after applying CTAC 1% by weight Solubility Characteristic Measured .sub.//[S/m] 3.1 10.sup.6 1.7 10.sup.5 Converted .sub.//[S/cm] 3.17 10.sup.4 1.74 10.sup.3 Measured .sub.[S/m] 1.3 10.sup.6 9.8 10.sup.6 Converted .sub.[S/cm] 1.33 10.sup.4 1.00 10.sup.3 Haze (30 V) (%) 41.7 92.8 Haze (40 V) (%) 88.0 95.4 Haze (60 V) (%) 95.7 96.2 T (0 V 40 V) (%) 39.5 37.2 T (0 V 60 V) (%) 44.3 39.9

DESCRIPTION OF REFERENCE NUMERALS

[0136] 101: liquid crystal layer

[0137] 102: liquid crystal compound

[0138] 201A, 201B: substrate

[0139] 301A, 301B: electrode layer

[0140] 401A, 401B: vertical alignment film