Reflectance-Variable Mirror

Abstract

A reflectance-variable mirror using a liquid crystal cell is disclosed herein. In an embodiment, the reflectance-variable mirror may comprise a first liquid crystal cell including a guest host liquid crystal layer, a first reflective polarizing film, a second liquid crystal cell including a retardation-variable liquid crystal layer, a second reflective polarizing film and an absorbing plate sequentially. The reflectance-variable mirror can realize excellent reflectance-variable characteristics by lowering the reflectance in an antireflection mode.

Claims

1. A reflectance-variable mirror sequentially comprising: a first liquid crystal cell having a guest host liquid crystal layer, wherein the guest host liquid crystal layer including liquid crystals and anisotropic dyes, a first reflective polarizing film having a first reflection axis formed in one direction, a second liquid crystal cell having a retardation-variable liquid crystal layer, wherein the retardation-variable liquid crystal layer is capable of switching between a phase difference mode and a non-phase difference mode, wherein, in the phase difference mode, a vibration direction of linearly polarized light is rotated by 90 degrees when passing through the retardation-variable liquid crystal layer, a second reflective polarizing film having a second reflection axis parallel to the first reflection axis and an absorbing plate.

2. The reflectance-variable mirror according to claim 1, wherein the guest host liquid crystal layer is capable of switching between a vertically oriented state and a horizontally oriented state when a voltage is applied.

3. The reflectance-variable mirror according to claim 1, wherein the first liquid crystal cell further comprises first and second alignment films disposed on opposing sides of the guest host liquid crystal layer.

4. The reflectance-variable mirror according to claim 1, wherein the first liquid crystal cell further comprises first and second transparent electrode substrates disposed on opposing sides of the guest host liquid crystal layer.

5. The reflectance-variable mirror according to claim 1, wherein the first reflective polarizing film has a first transmission axis orthogonal to the first reflection axis, and the first reflection axis and the first transmission axis are formed in a horizontal direction.

6. The reflectance-variable mirror according to claim 1, wherein the first reflection axis of the first reflective polarizing film is parallel to an absorption axis direction of the anisotropic dyes upon horizontal orientation of the guest host liquid crystal layer,

7. The reflectance-variable mirror according to claim 1, wherein the retardation-variable liquid crystal layer is capable of switching between the phase difference mode and the non-phase difference mode when a voltage is applied.

8. The reflectance-variable mirror according to claim 1, wherein the second liquid crystal cell further comprises third and fourth alignment films disposed on opposing sides of the retardation-variable liquid crystal layer.

9. The reflectance-variable mirror according to claim 1, wherein the second liquid crystal cell further comprises third and fourth transparent electrode substrates disposed on opposing sides of the retardation-variable liquid crystal layer.

10. The reflectance-variable mirror according to claim 1, wherein the second liquid crystal cell is a 90 degree TN mode liquid crystal cell, a 270 degree STN mode liquid crystal cell, an ECB mode liquid crystal cell, or a laminate of a wave plate and a VA mode liquid crystal cell.

11. The reflectance-variable mirror according to claim 1, wherein the second reflective polarizing film has a second transmission axis orthogonal to the second reflection axis, and the second reflection axis and the second transmission axis are formed in a horizontal direction.

12. The reflectance-variable mirror according to claim 1, wherein the second reflection axis of the second reflective polarizing film is parallel to the vibration direction of the linearly polarized light passing through the retardation-variable liquid crystal layer in the phase difference mode.

13. The reflectance-variable mirror according to claim 1, wherein the reflectance-variable mirror realizes a mirror mode when the first liquid crystal cell is in a vertically oriented state and the second liquid crystal cell is in the phase difference mode.

14. The reflectance-variable mirror according to claim 1, wherein the reflectance-variable mirror realizes an antireflection mode when the guest host liquid crystal layer is in a horizontally oriented state and the retardation-variable liquid crystal layer is in the non-phase difference mode.

15. The reflectance-variable mirror according to claim 1, wherein the reflectance-variable mirror comprises no image display panel.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0068] FIG. 1 illustrates the principle of implementing a mirror mode of a reflectance-variable mirror of the present application.

[0069] FIG. 2 illustrates the principle of implementing an antireflection mode of a reflectance-variable mirror of the present application.

[0070] FIG. 3A illustrates an exemplarily reflectance-variable mirror of Example 1 when no voltage is applied.

[0071] FIG. 3B illustrates the exemplarily reflectance-variable mirror of Example 1 when voltage is applied.

[0072] FIG. 4A illustrates an exemplarily reflectance-variable mirror of Comparative Example 1.

[0073] FIG. 4B illustrates an exploded view of the exemplarily reflectance-variable mirror of Comparative Example 1.

EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS

[0074] 10: guest host liquid crystal layer 101: liquid crystal 102: anisotropic dye 11A and 11B: first and second alignment films 12A and 12B: first and second transparent electrode substrates, 20: first reflective polarizing film 30: retardation-variable liquid crystal layer 301: liquid crystal 31A and 31B: third and fourth alignment films, 32A and 32B: third and fourth transparent electrode substrates 40: second reflective polarizing film 50: absorbing plate 60: guest host liquid crystal layer 601: liquid crystal 602: anisotropic dye 61A, 61B: alignment films 62A, 62B: transparent electrode layers 63: base layer 70: wave plate 80: mirror R.sub.1: reflection axis of first reflective polarizing film R.sub.2: reflection axis of second reflective polarizing film a: absorption axis of guest host liquid crystal layer (60) o: optical axis of wave plate (70)

Mode for Invention

[0075] Hereinafter, the reflectance-variable mirror of the present application will be described in detail by way of examples, but the scope of the present application is not limited by the following contents.

PRODUCTION EXAMPLE 1

Production of VA Mode GHLC Cell

[0076] Two cell substrates, in which an ITO electrode layer and a vertical alignment film were sequentially formed on a polycarbonate film (widthlength=15 cm5 cm), were spaced apart so that the vertical alignment films faced each other and a cell gap was 8 m, and the VA mode GHLC cell was produced by injecting a liquid crystal composition therein and sealing the edge. The liquid crystal composition comprises nematic liquid crystals (HNG7306 from HCCH, dielectric anisotropy: 5.0) and anisotropic dyes (X12 from BASF), where the anisotropic dye has a content of 1.4 wt %.

PRODUCTION EXAMPLE 2

Production of VA Mode GHLC cell

[0077] Two cell substrates, in which an ITO electrode layer and a vertical alignment film were sequentially formed on a polycarbonate film (widthlength=15 cm5 cm), were spaced apart so that the vertical alignment films faced each other and a cell gap was 8 m, and the VA mode GHLC cell was produced by injecting a liquid crystal composition therein and sealing the edge. The liquid crystal composition comprises nematic liquid crystals (HNG7306 from HCCH, dielectric anisotropy: 5.0) and anisotropic dyes (X12 from BASF), where the anisotropic dye has a content of 1.0 wt %.

PRODUCTION EXAMPLE 3

Production of ECB Mode GHLC Cell

[0078] Two cell substrates, in which an ITO electrode layer and a horizontal alignment film were sequentially formed on a glass (widthlength=15 cm5 cm), were spaced apart so that the orientation directions of the facing horizontal alignment films were parallel and a cell gap was 11 m, and then the ECB mode GHLC cell was produced by injecting a liquid crystal composition therein and sealing the edge. The liquid crystal composition comprises nematic liquid crystals (HPC2160 from HCCH, dielectric anisotropy: 18.2) and anisotropic dyes (X12 from BASF), where the anisotropic dye has a content of 1.5 wt %.

PRODUCTION EXAMPLE 4

Production of VA Mode GHLC Cell

[0079] Two cell substrates, in which an ITO electrode layer and a vertical alignment film were sequentially formed on a polycarbonate film (widthlength=15 cm5 cm), were spaced apart so that the vertical alignment films faced each other and a cell gap was 12 m, and the VA mode GHLC cell was produced by injecting a liquid crystal composition therein and sealing the edge. The liquid crystal composition comprises nematic liquid crystals (HNG7306 from HCCH, dielectric anisotropy: 5.0) and anisotropic dyes (X12 from BASF), where the anisotropic dye has a content of 1.4 wt %.

PRODUCTION EXAMPLE 5

Production of TN Mode Liquid Crystal Cell

[0080] Two cell substrates, in which an ITO electrode layer and a horizontal alignment film were sequentially formed on a polycarbonate film (widthlength=15 cm5 cm), were spaced apart so that the orientation directions of the facing horizontal alignment films were orthogonal and a cell gap was 7 m, and a 90 degree TN mode GHLC cell was produced by injecting a liquid crystal composition therein and sealing the edge. The liquid crystal composition comprises nematic liquid crystals (MAT-16-970 from Merck, dielectric anisotropy: 5.0) and a chiral agent (S811, HCC), where the chiral agent has a content of 0.08 wt %. The cell gap x An (refractive index anisotropy of liquid crystal) value of the produced TN mode liquid crystal cell is about 480 nm.

EXAMPLE 1

[0081] Each DBEF (dual brightness enhancement film, 3M) having a reflectance of 52% for unpolarized incident light was prepared as first and second reflective polarizing films. A black sheet (LG Chem) having an absorptivity of 98% or more was prepared as an absorbing plate.

[0082] The VA mode GHLC cell (10) of Production Example 1, the first reflective polarizing film (20), the TN mode liquid crystal cell (30) of Production Example 5, the second reflective polarizing film (40) and the light-absorbing plate (50) were sequentially laminated as in FIG. 3 to manufacture a reflectance-variable mirror. The reflection axis (R.sub.1) of the first reflective polarizing film and the reflection axis (R.sub.2) of the second reflective polarizing film were disposed so as to be parallel to each other. The reflection axis of the first reflective polarizing film was disposed to be parallel to the absorption axis direction upon horizontal orientation of the GHLC cell and the reflection axis of the second reflective polarizing film was disposed to be orthogonal to the orientation direction of the side of the second reflective polarizing film of the TN mode liquid crystal cell.

EXAMPLE 2

[0083] A reflectance-variable mirror was manufactured in the same manner as in Example 1, except that the VA mode GHLC cell of Production Example 2 was used instead of the VA mode GHLC cell of Production Example 1.

COMPARATIVE EXAMPLE 1

[0084] The ECB mode GHLC cell (60) of Production Example 3, a wave plate (70) and a commercial mirror (80) having a reflectance of 90% were sequentially laminated as in FIG. 4A to manufacture a reflectance-variable mirror. As illustrated in FIG. 4B, the absorption axis (a) upon horizontal orientation of the GHLC cell and the optical axis (o) of the wave plate were disposed to form about 45 degrees.

COMPARATIVE EXAMPLE 2

[0085] reflectance-variable mirror was manufactured in the same manner as in Comparative Example 1, except that the VA mode GHLC cell of Production Example 4 was used instead of the ECB mode GHLC cell of Production Example 3.

COMPARATIVE EXAMPLE 3

[0086] A reflectance-variable mirror was manufactured with the same structure as Example 2, except the first liquid crystal cell was omitted.

EVALUATION EXAMPLE 1

Evaluation of Reflectance-Variable Characteristics

[0087] For the GHLC cells used in manufacturing the reflectance-variable mirrors of Examples 1 to 2 and Comparative Examples 1 to 3, each transmittance depending on the presence or absence of voltage application was measured and described in Table 1 below. For the reflectance-variable mirrors of Examples 1 and 2 and Comparative Examples 1 to 3, each reflectance was measured depending on the presence or absence of voltage application and described in Table 1 below.

[0088] The transmittance is a back light transmittance, and the reflectance is a front light reflectance. The front light is light entering the reflectance-variable mirror from the viewer side, the back light is light entering the reflectance-variable mirror from the opposite side of the viewer side, and the back light transmittance and the front light reflectance are values measured at the viewer side.

[0089] In Examples 1 to 2 and Comparative Examples 1 to 3, the viewer side is the GHLC cell side. The reflectance is a value measured with respect to light having a wavelength of 380 nm to 780 nm by an SCI (specular component included) method using CM-2600d from KONICA MINOLTA. The front light reflectance in Table 2 is a numerical value when each front light incident light quantity is set to 100%.

TABLE-US-00001 TABLE 1 GHLC Cell single item characteristic 0 V Transmittance (%) 15 V Transmittance (%) Production Example 1 71.5 41 Production Example 2 77 46 Production Example 3 35 58.6 Production Example 4 59 33

TABLE-US-00002 TABLE 2 Reflectance-variable mirror characteristic 0 V 15 V Reflectance Reflectance (%) Reflectance (%) difference (%) Example 1 57.7 3.5 54.2 Example 2 68 9 59 Comparative 16 55 39 Example 1 Comparative 55 12.5 42.5 Example 2 Comparative 91% 51% 40 Example 3