Liquid crystal element

Abstract

The present application relates to a liquid crystal element and a use of the liquid crystal element. The exemplary liquid crystal element of the present application is, for example, an element capable of realizing a normally transparent mode, having a high contrast ratio, and being driven with a low driving voltage. Such a liquid crystal element may be applied in a variety of light modulators including a smart window, a window protective film, a flexible display element, an active retarder for displaying a 3D image and a viewing angle controlling film.

Claims

1. A liquid crystal element, comprising: a first substrate on which a mold layer having a convex part and a concave part is formed; a second substrate on which a resin layer having a surface energy of 45 mN/m or less an AFM Z-scale surface roughness of 2 nm or less and a pressure-sensitive adhesive strength is formed to be in contact with the convex part of the mold layer; and a liquid crystal compound present in the concave part of the mold layer and being in contact with the resin layer such that the resin layer effectively induce vertical alignment to liquid crystals, wherein the resin layer and the convex part of the mold layer are in contact with each other by the pressure-sensitive adhesive strength of the resin layer, or crosslinked with each other, the mold layer further includes a surface which is entirely in contact with and covering the first substrate, and the resin layer comprises a curable silicone compound.

2. The element of claim 1, wherein the mold layer or the resin layer satisfies General Equation 1 below:
0|Y{110.sup.4X.sup.31.210.sup.3X.sup.2+3.110.sup.3X1.610.sup.3}|0.05[General Equation 1] where X is an AFM Z-scale surface roughness of the mold layer or the resin layer, and Y is a surface polarity of the mold layer or the resin layer (however, the surface roughness and the surface polarity of the mold layer are values measured with respect to the surface of the mold layer in which the convex part and the concave part are not formed).

3. The element of claim 1, wherein the resin layer includes a polymerizable or crosslinkable compound or a curable compound.

4. The element of claim 3, wherein the polymerizable or crosslinkable compound is an acrylate compound.

5. The element of claim 3, wherein the mold layer or the resin layer further includes an additive capable of inducing vertical alignment.

6. The element of claim 5, wherein the additive includes a vertically-aligned polymer containing chlorine (Cl), fluorine (F) or silicon (Si).

7. The element of claim 1, wherein, in an initial state, the liquid crystal element has an in-plane retardation of 30 nm or less, or a retardation in a thickness direction of 500 nm or more.

8. The element of claim 1, which has a transmittance of 45% or more with respect to light having a wavelength of 400 to 700 nm, and a haze of 10% or less in an initial state.

9. The element of claim 8, which is switched to a scattering mode in which a transmittance of less than 45% with respect to light having a wavelength of 400 to 700 nm, and a haze of more than 10% due to the application of external energy.

10. A method of manufacturing a liquid crystal element, comprising: injecting a liquid crystal compound into a concave part of a first substrate on which a mold layer having a convex part and a concave part is formed, and stacking a second substrate on which a resin layer having a surface energy of 45 mN/m or less, an AFM Z-scale surface roughness of 2 nm or less and a pressure-sensitive adhesive strength is formed on the first substrate to be in contact with the convex part of the mold layer so that the liquid crystal compound is in contact with the resin layer such that the resin layer effectively induce vertical alignment to liquid crystals, wherein the resin layer and the convex part of the mold layer are in contact with each other by the pressure-sensitive adhesive strength of the resin layer, or crosslinked with each other, and the mold layer further includes a surface which is entirely in contact with and covering the first substrate.

11. The method of claim 10, wherein the convex part and the concave part of the mold layer are formed by an imprinting method.

12. A light modulator comprising the liquid crystal element of claim 1.

13. A liquid crystal element, comprising: a first substrate on which a mold layer having a convex part and a concave part is formed; a second substrate on which a resin layer having a surface energy of 45 mN/m or less an AFM Z-scale surface roughness of 2 nm or less and a pressure-sensitive adhesive strength is formed to be in contact with the convex part of the mold layer; and a liquid crystal compound present in the concave part of the mold layer and being in contact with the resin layer such that the resin layer effectively induce vertical alignment to liquid crystals, wherein the resin layer and the convex part of the mold layer are in contact with each other by the pressure-sensitive adhesive strength of the resin layer, or crosslinked with each other, the mold layer further includes a surface which is entirely in contact with and covering the first substrate, and the resin layer is a single layer in contact with both the liquid crystal compound and the convex part of the mold layer.

14. The element of claim 13, wherein the resin layer includes a polymerizable or crosslinkable compound or a curable compound.

15. The element of claim 13, wherein the polymerizable or crosslinkable compound is an acrylate compound.

16. The element of claim 13, wherein the resin layer further includes an additive capable of inducing vertical alignment.

17. The element of claim 16, wherein the additive includes a vertically-aligned polymer containing chlorine (Cl), fluorine (F) or silicon (Si).

18. A liquid crystal element, comprising: a first substrate on which a mold layer having a convex part and a concave part is formed; a second substrate on which a resin layer having a surface energy of 45 mN/m or less an AFM Z-scale surface roughness of 2 nm or less and a pressure-sensitive adhesive strength is formed to be in contact with the convex part of the mold layer; and a liquid crystal compound present in the concave part of the mold layer and being in contact with the resin layer such that the resin layer effectively induce vertical alignment to liquid crystals, wherein the resin layer and the convex part of the mold layer are in contact with each other by the pressure-sensitive adhesive strength of the resin layer, or crosslinked with each other, the mold layer further includes a surface which is entirely in contact with and covering the first substrate, the resin layer comprises a curable silicone compound, and the resin layer is a single layer in contact with both the liquid crystal compound and the convex part of the mold layer.

19. The element of claim 18, wherein the resin layer includes a polymerizable or crosslinkable compound or a curable compound.

20. The element of claim 19, wherein the polymerizable or crosslinkable compound is an acrylate compound.

21. The element of claim 19, wherein the resin layer further includes an additive capable of inducing vertical alignment.

22. The element of claim 21, wherein the additive includes a vertically-aligned polymer containing chlorine (Cl), fluorine (F) or silicon (Si).

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram of an exemplary liquid crystal element.

(2) FIG. 2 shows a method for manufacturing an exemplary liquid crystal element.

(3) FIG. 3 shows vertical alignment of liquid crystals according to surface characteristics of base films of References 1 to 6.

(4) FIG. 4 is an OM image showing vertical alignment of Example 1 and Comparative Example 1.

(5) FIG. 5 shows evaluation results for peel strengths of Example 1 and Comparative Example 1.

(6) FIG. 6 shows evaluation results for specular transmittances according to a viewing angle of Example 1 and Comparative Example 1.

(7) FIG. 7 shows evaluation results for total transmittances according to a driving voltage of Example 1 and Comparative Example 1.

MODES OF THE INVENTION

(8) Hereinafter, the above descriptions will be explained in further detail with reference to examples and comparative examples, but the scope of the present application is not limited by the following descriptions.

Measurement Example 1. Measurement of Surface Energy

(9) Surface energy was measured using a drop-shape analyzer (DSA100 manufactured by KRUSS). An average was obtained from five values of contact angles obtained by repeating a procedure for measuring a contact angle by dropping deionized water having a known surface tension onto a test sample five times, and an average was obtained from five values of contact angles obtained using diiodomethane having a known surface tension in the same manner as used above. Afterward, using the average values of the contact angles for deionized water and diiodomethane, surface energy was calculated by substituting a value (Strom value) of the surface tension of a solvent according to the Owens-Wendt-Rabel-Kaelble method. The surface energy (.sup.surface) of the sample may be calculated by considering a dispersion force between non-polar molecules and an interactive force between polar molecules (.sup.surface=.sup.dispersion+.sup.polar) and in the surface energy (.sup.surface), a ratio of the polar term (.sup.polar) may be defined as a polarity of the surface.

Measurement Example 2. Measurement of Surface Roughness

(10) A surface roughness may be measured by measuring an AFM Z-scale surface roughness (arithmetic average roughness, Ra) using a multimode AFM instrument manufactured by Bruker (Measurement Conditions: ParameterMode: ScanAsyst in air, Samples/line: 512512, Scan rate: 0.7 Hz, AFM probe: Silicon tip on nitride lever w/A1 coating (Bruker), Material: Silicon Nitride, Resonance Frequency: 50-90 kHz, Force Constant: 0.4 N/m, Thickness: 0.65 m, Length: 11510 m, Width: 25 m, Tip height: 5 m, Software-Nanoscope 8.15)

(11) Reference 1

(12) Two base films each having an ITO layer deposited on a polycarbonate (PC) film were placed to face each other such that the ITO layers were placed inside, and a liquid crystal composition (7306, HCCH) was injected thereinto to have a thickness of approximately 3 to 30 thereby manufacturing a liquid crystal cell.

(13) Reference 2

(14) Two base films each obtained by depositing an ITO layer on a PC film and performing corona treatment were placed to face each other such that the ITO layers were placed inside, and a liquid crystal composition (7306, HCCH) was injected thereinto to have a thickness of approximately 3 to 30 thereby manufacturing a liquid crystal cell.

(15) Reference 3

(16) Two base films each obtained by depositing an ITO layer on a polyethyleneterephthalate (PET) film and transferring an Si-adhesive manufactured by Daipo Paper to the ITO layer to have a thickness of approximately 7 to 50 m were placed to face each other such that adhesive layers were placed inside, and a liquid crystal composition (7306, HCCH) was injected thereinto to have a thickness of approximately 3 to 30 thereby manufacturing a liquid crystal cell.

(17) Reference 4

(18) Two base films each obtained by depositing an ITO layer on a PC film and forming an SiOx-based barrier layer on the ITO layer were placed to face each other such that the barrier layers were placed inside, and a liquid crystal composition (7306, HCCH) was injected thereinto to have a thickness of approximately 3 to 30 thereby manufacturing a liquid crystal cell.

(19) Reference 5

(20) Two base films each obtained by forming a hard coating layer on a PC film were placed to face each other such that the hard coating layers were placed inside, and a liquid crystal composition (7306, HCCH) was injected thereinto to have a thickness of approximately 3 to 30 m, thereby manufacturing a liquid crystal cell.

(21) Reference 6

(22) Two base films each obtained by depositing an ITO layer on a PET film and transferring a 3193H adhesive manufactured by Henkel to the ITO layer to have a thickness of approximately 1 to 5 m such that the adhesive layers were placed inside, and a liquid crystal composition (7306, HCCH) was injected thereinto to have a thickness of approximately 3 to 30 m, thereby manufacturing a liquid crystal cell.

Evaluation Example 1. Evaluation of Vertical Alignment According to Surface Characteristic

(23) Surface energy and surface roughness were measured on the base films manufactured in References 1 to 6 by the above methods described above, and the results are shown in FIG. 3 and Table 1. Vertical alignment was evaluated with respect to the liquid crystal cells manufactured in References 1 to 6, and the results are shown in Table 1. Specifically, the surface energy and surface roughness may be measured by Measurement Examples 1 and 2, respectively, and when the liquid crystal cell was observed at the front (incident angle: 0), if the specular transmittance is 55% or more, it was evaluated to be vertically aligned. As shown in FIG. 3 and Table 1, it can be seen that, when the base film has a surface energy of 45 mN/m or less and a surface roughness of 2 nm or less, a liquid crystal cell using the above base films as upper and lower base films may effectively induce vertical alignment of liquid crystals.

(24) TABLE-US-00001 TABLE 1 Surface energy Surface roughness Transmit- Vertical (mN/m) (Ra, nm) tance(%) alignment Reference 1 23.1 0.4 66 (PC-ITO) Reference 2 29.7 0.4 65 (PC-ITO_C) Reference 3 8.5 1.3 69 (Si-A) Reference 4 61.0 2.3 48 X (Barrier) Reference 5 46.5 11.4 45 X (H/C) Reference 6 47.9 0.3 52 X (3193HS)

Example 1

(25) A honeycomb-type pattern was formed by coating a composition for an acrylic mold layer (Trade Name: KAD-03, Manufacturer: MINUTA Tech.) on an ITO layer of a PET film (100 mm100 mm) (hereinafter, referred to as a first substrate) on which the ITO transparent electrode layer was deposited, and performing an imprinting method (width of a convex part of the pattern: 10 m50 m, height of the convex part: 3 m20 m, width of a concave part: 300 m750 m). Subsequently, a liquid crystal composition including 2 g of a liquid crystal compound (7306, HCCH) and 20 mg of a dichroic dye (X12, BASF) was coated on the imprinted mold layer. Afterward, an Si-Adhesive manufactured by Daipo Paper as a resin layer was transferred onto a PET film (100 mm100 mm) on which an ITO transparent electrode layer is deposited (hereinafter, referred to as a second substrate) to have a thickness of approximately 10 Subsequently, the second substrate was stacked on the first substrate such that the resin layer was in contact with the concave part of the mold layer, and light was applied under conditions of Fusion UV 70% 3 m/min, thereby manufacturing a liquid crystal element.

Comparative Example 1

(26) A liquid crystal element of Comparative Example 1 was manufactured by the same method as described in Example 1, except that a 3193H adhesive manufactured by Henkel, instead of an Si-adhesive manufactured by Daipo Paper, as a resin layer, was transferred onto a second substrate to have a thickness of approximately 3 m.

Evaluation Example 2. Evaluation of Vertical Alignment of Liquid Crystal Element According to Example and Comparative Example

(27) The liquid crystal elements manufactured in Example 1 and Comparative Example 1 were observed by a microscope (OM), which are shown in FIG. 4. As shown in FIG. 4, it can be confirmed that, in the case of Comparative Example 1, since liquid crystals and dyes are not vertically aligned, a domain is formed and looks dark. However, in the case of Example 1, since liquid crystals and dyes are vertically aligned, a domain is not observed, and looks brighter.

Evaluation Example 3. Evaluation of Adhesive Strength

(28) Adhesive strengths were evaluated by measuring 90-degree peel strengths of the resin layer and the mold layer on the liquid crystal elements manufactured in Example 1 and Comparative Example 1 using a texture analyzer, which are shown in FIG. 5 and Table 1. As shown in FIG. 5, it can be seen that Example 1 has an excellent adhesive strength, compared to Comparative Example 1.

Evaluation Example 4. Evaluation of Transmittance

(29) A specular transmittance according to a viewing angle in a state in which a voltage was not applied was evaluated with respect to the liquid crystal elements manufactured in Example 1 and Comparative Example 1, which is shown in FIG. 6, and a total transmittance according to a driving voltage at the front was evaluated, which is shown in FIG. 7. The specific transmittance according to a viewing angle was evaluated by measuring a change in specular transmittance according to an angle of light incident to the liquid crystal element using LCMS-200 equipment, and to evaluate the transmittance according to the application of a voltage, a total transmittance according to a voltage applied by driving an AC power source connected to an ITO layer of the upper and lower ITO-PET films was measured using a hazemeter (NDH-5000SP). As shown in FIG. 7, the liquid crystal element of Example 1 has a high transmittance when a voltage is not applied, and has a low transmittance when a voltage is applied, and thereby, it can be seen that the liquid crystal element realizes a normally transparent mode. Also, as shown in FIG. 6, it can be seen that the liquid crystal element of Example 1 has a high transmittance, that is, an excellent vertical alignment state at the front and viewing angle, compared with the liquid crystal element of Comparative Example 1.