JP2007133187A - Reflection dimmer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflection dimmer that can not only reduce the heat load to suppress the re-radiation or dispersion of the absorbed heat but also control the transmissivity as desired and almost instantly control the transmissivity even if it is made large and further can be used as a privacy protection window material. <P>SOLUTION: This reflection dimmer has a pair of transparent electrodes 2A, 2B facing each other, an optical function layer 3 retained between those transparent electrodes 2A, 2B, and an electric field controller 20 to apply or cancel an electric field between those transparent electrodes 2A, 2B. The optical function layer 3 has a irregular transparent surface layer 3A with recesses 3C, and constitutes a reflection dimmer 11 with the liquid crystal materials filling those recesses 3C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reflective dimmer that can be switched between a light reflection state and a light transmission state by applying and releasing an electric field.

  As a conventional dimmer, one using an electrochromic (EC) material or one using liquid crystal is known.

  Examples of the light control body using the EC material include those having a structure in which an EC substance layer and an electrolyte are sandwiched between a pair of transparent electrodes, as in Patent Document 1, and by passing a current through the transparent electrodes. An EC substance is caused to undergo a redox reaction to cause a change in light absorption.

Moreover, as a light control body using a liquid crystal, as disclosed in Patent Document 2, a liquid crystal is encapsulated in a microcapsule and dispersed in a resin matrix, and an electric field is applied from the upper and lower surfaces through transparent electrodes. It is done. In this dimmer, the liquid crystal molecules are aligned along the microcapsule wall, and the optical axis direction of the liquid crystal molecules in each capsule is random when no electric field is applied. Become. On the other hand, when an electric field is applied to align the alignment direction of the liquid crystal molecules with the electric field direction, the transmitted light hardly scatters and changes to transparent.
Japanese Patent Publication No. 6-93067 Japanese Patent Publication No. 3-52843

  By the way, the light control body using EC material controls the transmitted light by causing a change in light absorption. Therefore, when used as a window material for automobiles, the temperature of the light control body itself rises due to absorbed light and is re-radiated into the passenger compartment as radiant heat, so there is a limit to heat insulation. In addition, since it is a current-driven dimmer, there is a problem that when the area is increased, a loss due to internal resistance occurs, and the response speed is greatly reduced.

  In addition, a light control body in which liquid crystal is sealed in a microcapsule still transmits most of the scattered light through the light control body even in an opaque state where no electric field is applied. There is a problem that the ability to mitigate direct light penetration into the room is poor.

  In particular, when the light control body is used as a window material for automobiles, means for suppressing re-radiation of absorbed heat into the passenger compartment and scattered transmitted light is strongly desired. In addition to reducing the thermal load, the dimmer is also required to be used as a privacy protection window material that can arbitrarily control the transmittance. For this purpose, the transmittance can be controlled almost instantaneously even if the area is increased. It is requested to be possible.

  The present invention not only relieves the heat load of absorbing absorbed heat and can suppress scattered transmitted light, but also can arbitrarily control the transmittance, and can control the transmittance almost instantaneously even when the area is increased. It is an object of the present invention to provide a reflective dimmer that can also be used as a privacy protection window material.

  In order to achieve the above object, a reflective dimmer according to the present invention includes a pair of opposing transparent electrodes, an optical functional layer sandwiched between the transparent electrodes, and an electric field applied between the transparent electrodes. Electric field control means for releasing the electric field, wherein the optical functional layer is composed of a transparent surface uneven layer having a plurality of recesses on the surface, and a liquid crystal material filled in each recess. .

  According to the reflective dimmer configured as described above, the electric field is applied / released by the electric field control means, and is formed in each concave portion of the transparent surface uneven layer constituting the optical functional layer sandwiched between the transparent electrodes. By changing the orientation of the filled liquid crystal, the dimmer can be changed between a light reflection state and a light transmission state. Therefore, when used as a window material for automobiles, not only the thermal load can be suppressed, but also the transmittance can be controlled arbitrarily, and the transmittance can be arbitrarily controlled. The transmittance can be controlled almost instantaneously, and it can also be used as a privacy protection window material.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a reflective dimmer according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing a reflective dimmer according to the present invention. FIG. 2 is an enlarged cross-sectional view showing a portion A of FIG. 1 without applying an electric field, and FIG. 3 is an enlarged cross-sectional view showing a portion A of FIG. 1 with an electric field applied. FIG. 4 is a diagram for explaining the refractive index anisotropy of the liquid crystal material.

  As shown in FIG. 1, the reflective dimmer 11 according to the present invention includes a pair of transparent electrodes 2A and 2B facing each other, the optical functional layer 3 sandwiched between the transparent electrodes 2A and 2B, and the above And an electric field control means 20 capable of applying an electric field between the transparent electrodes 2A and 2B and releasing the electric field.

  The transparent electrodes 2A and 2B are respectively supported on the opposing surface sides of the pair of transparent substrates 1A and 1B facing each other. That is, the transparent base materials 1A and 1B sandwich the transparent electrodes 2A and 2B sandwiching the optical function layer 3 from the outside, and the sealing material 4 is provided at both ends of the transparent electrodes 2A and 2B and the optical function layer 3. Is installed.

  The electric field control means 20 is constituted by a closed circuit 21 having a power source 5, a switch 6 and a variable resistor 7. The electric field control means 20 can adjust the voltage by changing the resistance value of the variable resistor 7, and can apply an electric field between the transparent electrodes 2A and 2B by turning on / off the switch 6, Or cancel the electric field.

  As shown in FIGS. 2 and 3, the optical functional layer 3 is composed of a transparent surface uneven layer 3B having a plurality of recesses 3C on the surface, and a liquid crystal material 3A filled in each recess 3C. As for the cross-sectional shape of the concave portion of the transparent surface uneven layer 3B, the opening diameter or the opening width is gradually increased toward the opening side (upward in FIGS. 2 and 3).

When the switch 6 is turned off and no electric field is applied between the transparent electrodes 2A and 2B, the liquid crystal material 3A is randomly oriented as shown in FIG. 2, and the refraction of the concave portion 3C filled with the liquid crystal material 3A is as shown in FIG. rate is considered to have become substantially uniform in the liquid crystal approximate mean of the refractive index _n a ₌ normal refractive index _{n 0} of the material 3A and extraordinary refractive index _{n e (n 0 + 2n e} ) / 3 shown in FIG. 4 be able to. In this case, if approximate the average refractive index n _a and the refractive index n _b of the transparent surface irregularity layer 3B, the light adjuster can be transparent.

  On the other hand, as shown in FIG. 3, when the switch 6 is turned on and a sufficiently large electric field E is applied to the liquid crystal material 3A between the transparent electrodes 2A and 2B, the liquid crystal material 3A has a dielectric anisotropy. Orient accordingly. That is, when the dielectric anisotropy is negative, it is oriented in the direction perpendicular to the electric field E, and when the dielectric anisotropy is positive, it is oriented along the electric field E as shown in FIG.

In this oriented state, the refractive index of the recess 3C of the transparent surface uneven layer 3B is uniform, but since the cross-sectional shape of the recess 3C gradually increases toward the opening side, the transparent surface uneven layer 3B and its recess The refractive index of the entire optical functional layer 3 made of the liquid crystal material 3A in 3C gradually changes from the bottom of the recess 3C toward the opening side. <When the dielectric anisotropy is positive at _{n e,} or _n 0> relationship normal refractive index _{n 0} and the extraordinary refractive index _{n e} of the liquid crystal material 3A is _n 0 when the dielectric anisotropy is negative in _{n e} The refractive index of the optical functional layer 3 increases as it approaches the opening side. Conversely, when n ₀ < _ne and the dielectric anisotropy is negative, or when n ₀ > _ne and the dielectric anisotropy is positive, the optical function layer 3 has a smaller refractive index as it approaches the opening side. Become. That is, in order to obtain a highly reflective state when the electric field E is applied, it is necessary to select a liquid crystal material in consideration that the refractive index increases as it approaches the opening side of the optical functional layer 3.

The cross-sectional shape of the concave portion 3C of the transparent surface uneven layer 3B is not limited to a specific shape as long as the opening diameter or the opening width is gradually increased toward the opening side. Depending on the value of the refractive index n _0, n _e of the liquid crystal material to be used, it is preferable to increase the refractive index changes in the thickness direction of the optical functional layer 3 as much as possible, when the cross-sectional shape of the recess 3C is conical It is preferable to set the inclination angle with respect to the thickness direction of the concave slope to 45 ° or less. In addition, when the macro refractive index of the liquid crystal material 3A in the recess 3C is different from the refractive index of the transparent surface uneven layer 3B, that is, in order to prevent the liquid crystal material 3A from becoming opaque due to scattering of visible light, The size of the 3C opening needs to be set to 800 nm or less.

  The transparent surface uneven layer 3B can be produced by using, for example, a nanoimprint technique for transferring with a mold in which nano-order processing has been performed on the surface of a transparent resin or an inorganic sol-gel film. Such a mold can be manufactured by a photolithography technique, an anodic oxide film of aluminum, or the like.

  As the liquid crystal material 3A, various liquid crystal materials such as a smectic liquid crystal and a cholesteric liquid crystal can be used. In particular, the nematic liquid crystal has a small attractive force between molecules, and easily changes the molecular orientation when an electric field is applied to the liquid crystal. Therefore, it is particularly suitable for the reflective dimmer according to the present invention.

  In addition, the liquid crystal alignment control is a voltage drive method and can be controlled in an extremely short time, and therefore can be used as a privacy protection window material. Furthermore, as described above, if the variable resistor 7 is interposed in the closed circuit 21 and the voltage applied to the liquid crystal material 3A is adjusted, the alignment state of the liquid crystal material 3A can be controlled, and the optical functional layer can be controlled. Since the refractive index change in the thickness direction 3 can be controlled, the transmittance of the dimmer can be arbitrarily set between the maximum value and the minimum value.

  As the transparent electrodes 2A and 2B, a transparent semiconductor film having a band gap in the ultraviolet region can be used. Indium oxide doped with tin oxide (ITO), zinc oxide added with aluminum oxide or gallium oxide (ZnO), Antimony oxide, tin oxide doped with fluorine (SnO), or the like is most preferably used. When using ITO, the resistance can be made relatively small, and the film thickness should be set to a level at which light absorption in the visible light region is hardly a problem. It is most preferable to use a film thickness of about 100 to 150 nm. .

  Examples of the application of the reflective dimmer 10 according to the present invention to automobiles include window materials such as windshields, side windows, back windows, and sunroofs, and headlamp lenses for the purpose of headlamp orientation control. It is conceivable to apply, but the application is not limited to these.

  Various methods for calculating the optical characteristics of inhomogeneous films whose refractive index continuously changes in the thickness direction have been proposed. One of the representative techniques is based on multilayer film approximation. This is done by subdividing the inhomogeneous film in the thickness direction and regarding each subdivided portion as a single thin film having a uniform refractive index, assuming that they are deposited as a multilayer film, This is a method for calculating optical characteristics such as transmittance (reference: thin film handbook, Japan Society for the Promotion of Science, Thin Film 131 Committee, Ohmsha, p. 798, 1983).

  When this calculation method is applied to the reflective dimmer according to the present invention, a calculation model as shown in FIG. 5 is obtained. That is, the incident light 8 that has passed through the transparent substrate 1A interferes with each of the transparent electrode 2A, the thin film group 3 'having a different refractive index, and the transparent electrode 2B to generate reflected light 9. The remaining light becomes transmitted light 10 and travels through the transparent substrate 1B. At this time, when the intensity ratio of the reflected light 9 to the incident light 8 is defined as the reflectance R, R is expressed by the following formulas (1) to (8).

In the formulas (1) to (8), the meaning of each symbol is as follows.
r: Amplitude reflectance Y: Transparent base materials 1A, 1B, transparent electrodes 2A, 2B, the entire optical admittance n _s , ns _′ , _ne : transparent base material 1A, transparent base material 1B, comprising thin film group 3 ′ Refractive index h _{c of} transparent electrode 2A and transparent electrode 2B: film thickness n _{j of} transparent electrode 2A and transparent electrode 2B: refractive index h _{j of} thin film group 3 ′ from above thin film group 3 ′: from above thin film group 3 ′ Film thickness M _c , M _{c ′} , M _f , M _{s ′ of the} jth thin film: transparent base material 1A, transparent base material 1B, thin film group 3 ′, transparent base material 1B characteristic matrix δ _c : transparent electrode 2A and Phase film thickness δ _j of transparent electrode 2B: Phase film thickness of j-th thin film from above thin film group 3 ′ λ: wavelength of incident light 8 in vacuum In addition, in order to simplify the formula, light is a transparent substrate Assuming the case where light is incident vertically from 1A to the transparent electrode 2A, a material that does not absorb light is used as each constituent member. It is formulated in. The transparent electrodes 2A and 2B are assumed to be the same member and have the same film thickness. However, these restrictions are not restrictive, and are basically established even if there is a difference in film thickness between the oblique incidence, the absorbing member, and both transparent electrodes.

  Thus, according to the reflective dimmer 11 of the present embodiment, the transparent surface uneven layer 3B having a plurality of recesses 3C on the surface between the pair of opposing transparent electrodes 2A and 2B, and the recesses 3C. The optical functional layer 3 composed of the filled liquid crystal material is sandwiched, and the cross-sectional shape of the concave portion 3C is gradually enlarged toward the opening side. Then, the average refractive index of the two axes of the liquid crystal material 3A and the refractive index of the transparent surface uneven layer 3B are approximated, and an electric field is applied / released between the transparent electrodes 2A and 2B by the electric field control means 20, thereby By changing the orientation of the liquid crystal filled in each recess 3C of 3B, the dimmer 11 can be switched between a light transmission state (transparent state) and a reflection state (reflection mirror state). Therefore, when used as a window material for automobiles, not only the thermal load can be suppressed, but also the transmittance can be controlled arbitrarily, and the transmittance can be controlled arbitrarily. The transmittance can be controlled almost instantaneously, and it can also be used as a privacy protection window material.

  Examples of the reflective dimmer according to the present invention will be described below, but the present invention is not limited to these examples.

  FIG. 6 is a plan view showing the structure of the transparent surface uneven layer applied to this embodiment. 7 is a cross-sectional view taken along line BB in FIG.

  The whole structure of the light control body employs a structure as shown in FIG. As shown in FIGS. 6 and 7, the surface uneven structure of the transparent surface uneven layer 3 </ b> B assumes that a conical recess 3 </ b> C is arranged on a transparent resin flat plate vertically and horizontally, and an upper surface opening of the conical recess 3 </ b> C is provided. The size of the part was d and the depth was h. In this example, d = 100 nm was constant, and the spectral reflection spectrum was calculated and evaluated by the above formulas (1) to (8) and the following formulas (9) to (11) using the depth h as a parameter. .

Transparent soda lime glass (refractive index n _s = 1.52) was used for the transparent substrates 1A and 1B. The transparent electrodes 2A, the 2B, tin using doped indium oxide (ITO, the refractive index _n c = 2.10) were the 100nm thickness. As the liquid crystal material 3A filled in the concave portion 3C of the transparent surface uneven layer 3B, positive type 4-cyano-4′-pentylbiphenyl whose major axis direction is directed to the electric field direction when an electric field is applied was used. The refractive index of this liquid crystal material 3A (20 ° C., D light) is n ₀ = 1.54 in the minor axis direction and n _e = 1.72 in the major axis direction, and the average refractive index n when dispersed randomly. _a = 1.66.

Transparent surface uneven layer 3B material, Essilor Stylis 1.67 (trade name, Essilor Co., Ltd., refractive index _n b = 1.67) was.

In this calculation, the division number m = 10 of the thin film group 3 ′ in FIG. Therefore, h _j = h / m (1 ≦ j ≦ m), and the average refractive index n _j of the j-th thin film is given by the following equation from the average refractive index based on the volume fraction of the liquid crystal material 3A and the surface uneven layer 3B. expressed.

  FIG. 8 is a diagram illustrating calculation results of reflection spectra of Examples 1 to 4.

[Example 1]
In Example 1, h = 300 nm. As shown in FIG. 8, the reflectivity was 11% to 37% in the entire visible light range.

[Example 2]
In Example 2, h = 400 nm. As shown in FIG. 8, the reflectance was 14% or more in the entire visible light region, and particularly the high reflectance of 68% or more was shown in the region of 500 nm or less.

Example 3
In Example 3, h = 500 nm. As shown in FIG. 8, the reflectance was 18% or more in the entire visible light region, and particularly high in the region of 600 nm or less was 56% or more.

Example 4
In Example 4, h = 600 nm. As shown in FIG. 8, the reflectance was 18% or more in the entire visible light region, and in particular, the high reflectance of 58% or more was shown in the region of 700 nm or less.

Example 5
In Example 5, h = 700 nm. As shown in FIG. 8, the high reflectance of 69% or more was shown in the entire visible light region.

  The reflective dimmer according to the present invention can be applied to window materials for automobiles, headlamp lenses for automobiles, window materials for buildings, and the like, and can also be used as privacy protection window materials.

It is sectional drawing which shows typically the reflection type light control body which concerns on this invention. FIG. 2 is an enlarged cross-sectional view showing a portion A of FIG. FIG. 2 is an enlarged cross-sectional view illustrating a portion A of FIG. 1 and an electric field applied. It is a figure explaining the refractive index anisotropy of liquid crystal material. It is a figure which shows the calculation model of the reflectance of the reflection type light control body which concerns on this invention. It is a top view which shows the structure of the transparent surface uneven | corrugated layer applied to a present Example. It is the BB sectional view taken on the line of FIG. It is a figure which shows the calculation result of the reflection spectrum of Examples 1-5.

Explanation of symbols

1A, 1B transparent substrate,
2A, 2B transparent electrode,
3 optical functional layers,
3A liquid crystal material,
3B transparent surface uneven layer,
3C recess,
3 'thin film group,
4 Sealing material,
5 Power supply,
6 switches,
7 Variable resistance,
8 Incident light,
9 Reflected light,
10 Transmitted light,
11 reflective dimmer,
20 Electric field control means,
21 Closed circuit.

Claims (4)

A pair of transparent electrodes facing each other, an optical functional layer sandwiched between these transparent electrodes, and an electric field control means for releasing the electric field while applying an electric field between the transparent electrodes,
The optical functional layer is composed of a transparent surface uneven layer having a plurality of recesses on the surface, and a liquid crystal material filled in each recess.   2. The reflective dimmer according to claim 1, wherein a cross-sectional shape of the concave portion of the transparent surface uneven layer is sequentially enlarged toward the opening side.   The reflective light control body according to claim 1, wherein the liquid crystal material is a nematic liquid crystal material.   It forms as a window material for motor vehicles, The reflective light control body of any one of Claims 1-3 characterized by the above-mentioned.

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