Optical control element

Abstract

To provide an optical control element that emits light capable of accelerating the growth of plants.SOLUTION: An optical control element includes a light-emitting element, a reflection object, and a cholesteric liquid crystal element. The cholesteric liquid crystal element includes: a first substrate where a first electrode is provided; a second substrate where a second electrode is provided; and a cholesteric liquid crystal layer held between the first substrate and the second substrate. The cholesteric liquid crystal layer transmits right-handed circularly-polarized light and reflects left-handed circularly-polarized light.SELECTED DRAWING: Figure 1

Description

Technical Field

[0004] , , , , , , , , ,

[0005] , , , , , ,

[0001] Embodiments of the present invention relate to an optical control element.

Background Art

[0002] The growth of plants varies greatly depending on the quality of light. For example, it is known that growth is promoted when cultivated under right circularly polarized light irradiation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present embodiment provides an optical control element that irradiates light capable of promoting plant growth.

Means for Solving the Problems

[0006] [Figure 1] Figure 1 is a cross-sectional view showing an example of a schematic configuration of the optical control element of the embodiment. [Figure 2] Figure 2 is an exploded perspective view showing an example of a configuration that can be applied to a cholesteric liquid crystal element. [Figure 3] Figure 3 illustrates the arrangement of the cholesteric liquid crystal layers. [Figure 4] Figure 4 illustrates the arrangement of the cholesteric liquid crystal layers. [Figure 5] Figure 5 illustrates the reflection of circularly polarized light by the cholesteric liquid crystal layer. [Figure 6] Figure 6 illustrates the reflection of circularly polarized light by the cholesteric liquid crystal layer. [Modes for carrying out the invention]

[0007] The embodiments of the present invention will be described below with reference to the drawings. Note that the disclosure is merely an example, and modifications that can be easily conceived by those skilled in the art while maintaining the spirit of the invention are naturally included within the scope of the present invention. Furthermore, in order to clarify the explanation, the drawings may schematically represent the width, thickness, shape, etc., of each part compared to the actual embodiment, but these are merely examples and do not limit the interpretation of the present invention. In addition, in this specification and in each drawing, elements similar to those described above in previously shown drawings are denoted by the same reference numerals, and detailed explanations may be omitted as appropriate. The optical control element according to one embodiment will be described in detail below with reference to the drawings.

[0008] In this embodiment, the first direction X, the second direction Y, and the third direction Z are orthogonal to each other, but they may intersect at angles other than 90 degrees. The direction toward the tip of the arrow in the third direction Z is defined as up or upward, and the direction opposite to the direction toward the tip of the arrow in the third direction Z is defined as down or downward. The first direction X, the second direction Y, and the third direction Z may also be referred to as the X direction, the Y direction, and the Z direction, respectively.

[0009] Furthermore, when referring to "the second member above the first member" and "the second member below the first member," the second member may be in contact with the first member or may be located away from the first member. In the latter case, a third member may be interposed between the first member and the second member. On the other hand, when referring to "the second member above the first member" and "the second member below the first member," the second member is in contact with the first member.

[0010] Furthermore, assuming that there is an observation position for observing the optical control element at the tip of the arrow in the third direction Z, viewing from this observation position toward the XY plane defined by the first direction X and the second direction Y is called a planar view. Viewing the cross-section of the optical control element in the XZ plane defined by the first direction X and the third direction Z, or in the YZ plane defined by the second direction Y and the third direction Z, is called a cross-sectional view.

[0011] [Embodiment] Figure 1 is a cross-sectional view showing an example of a schematic configuration of the optical control element of the embodiment. The optical control element LCE comprises a mirror MRR, a cholesteric liquid crystal element CLS, and a light-emitting element LS. The light-emitting element LS has a red-emitting element LSR and a blue-emitting element LSB. The light-emitting element LS is provided between the cholesteric liquid crystal element CLS and the mirror MRR.

[0012] Below the optical control element LCE, the plant PLT is arranged. The cholesteric liquid crystal element CLS is provided between the light emitting element LS and the plant PLT. The plant PLT absorbs red light and blue light. Therefore, it is preferable that the light emitting element LS includes a light emitting element LSR that emits red light and a light emitting element LSB that emits blue light.

[0013] Although details will be described later, the cholesteric liquid crystal element CLS includes a cholesteric liquid crystal layer. The cholesteric liquid crystal layer reflects left circularly polarized light among red light and blue light.

[0014] The mirror MRR reflects the light emitted from the light emitting element LS. Instead of the mirror MRR, a reflector having the property of reflecting light, for example, a holographic optical element (HOE) may be arranged.

[0015] FIG. 2 is an exploded perspective view showing an example of a configuration applicable to a cholesteric liquid crystal element. The cholesteric liquid crystal element CLS includes a substrate SUB1, a substrate SUB2, and a cholesteric liquid crystal layer (not shown) provided between the substrate SUB1 and the substrate SUB2. The substrate SUB1 includes a base material BA1 and a strip electrode LE1. The substrate SUB2 includes a base material BA2 and a strip electrode UE1.

[0016] The strip electrode LE1 is provided in contact with the base material BA1, extends along the first direction X, and is arranged side by side along the second direction Y. The strip electrode UE1 is provided in contact with the base material BA2, extends along the second direction Y, and is arranged side by side along the first direction X.

[0017] Although not shown in FIG. 2, an alignment film is provided to cover each of the strip electrode LE1 and the strip electrode UE1.

[0018] The cholesteric liquid crystal layer is a liquid crystal layer composed of a cholesteric liquid crystal material. The cholesteric liquid crystal layer is driven by an electric field generated between the strip electrode LE1 and the strip electrode UE1, that is, a so-called longitudinal electric field.

[0019] The materials of base material BA1 and base material BA2 are, for example, transparent insulating substrates such as glass substrates or plastic substrates.

[0020] The strip-shaped electrodes LE1 and UE1 are transparent electrodes formed from transparent conductive materials such as indium tin oxide (ITO) or indium zinc oxide (IZO).

[0021] Cholesteric liquid crystal elements (CLS) are so-called passive matrix liquid crystal elements. However, CLS are not limited to this. Cholesteric liquid crystal elements (CLS) may also be active matrix liquid crystal elements having multiple switching elements.

[0022] Figures 3 and 4 illustrate the arrangement of cholesteric liquid crystal layers. Cholesteric liquid crystal layers possess the characteristic of bistableness (memory properties). Bistability refers to the ability to self-retain a planar state that reflects light, a focal conic state that transmits light, or an intermediate state between these. These states can be switched by adjusting the electric field strength applied to the cholesteric liquid crystal layer, in other words, by adjusting the voltage between the electrodes that hold the cholesteric liquid crystal layer.

[0023] Figure 3 shows the orientation of liquid crystal molecules in the cholesteric liquid crystal layer in the planar state. Figure 4 shows the orientation of liquid crystal molecules in the cholesteric liquid crystal layer in the focal conic state.

[0024] As shown in Figure 3, the liquid crystal molecules LM in the planar cholesteric liquid crystal layer rotate sequentially in the third direction Z to form a helical structure. The axis of rotation of the helical structure is approximately perpendicular to the XY plane on which the strip electrodes UE1 and LE1 are provided. In other words, the axis of rotation of the helical structure is aligned in a direction parallel to the third direction Z.

[0025] In this state, from the incident light LI, light of a predetermined wavelength corresponding to the helical pitch of the liquid crystal molecules LM is selectively reflected as reflected light LR by the cholesteric liquid crystal layer CLC1. If the average refractive index of the cholesteric liquid crystal layer is n and the helical pitch is p, then the wavelength λ at which reflection is maximized is λ = n × p. If the refractive indices of the long axis and short axis of the cholesteric liquid crystal layer are ne and n0, respectively, then the average refractive index n is expressed as n = (ne + n0) / 2 (Equation 1). Of the incident light LI, all light except the reflected light LR is transmitted as transmitted light LT and emitted from the cholesteric liquid crystal element CLS.

[0026] The pitch p of the cholesteric liquid crystal layer depends on the type of chiral agent or its concentration c, along with the polymerizable liquid crystal compound used to form the cholesteric liquid crystal layer. If β is the proportionality constant specific to the chiral agent, the wavelength λ can be expressed as λ = n × p = n / (β × c) (Equation 2).

[0027] The half-width Δλ of the selective reflection band exhibiting polarization-selective reflection depends on the birefringence Δn and pitch p of the cholesteric liquid crystal layer, and can be expressed as Δλ = Δn × p (Equation 3). Δn can be adjusted by controlling the type and mixing ratio of the polymerizable liquid crystal compound, or the temperature during orientation fixing, when forming the cholesteric liquid crystal layer.

[0028] In the cholesteric liquid crystal element CLS of this embodiment, the cholesteric liquid crystal layer CLC1 preferably has a refractive index Δn and pitch p that reflects red light, for example, light with a central wavelength λ = 625 nm to 780 nm, and blue light, for example, light with a central wavelength of 450 nm to 485 nm.

[0029] In the focal conic state, the liquid crystal molecules in the cholesteric liquid crystal layer rotate sequentially in a direction perpendicular to the third direction Z, i.e., parallel to the XY plane, to form a helical structure. The helical axis of the helical structure is parallel to the XY plane. In the focal conic state, the cholesteric liquid crystal layer CLC1 loses its selectivity for the reflected wavelength, and almost all of the incident light LI is transmitted as transmitted light LT.

[0030] The cholesteric liquid crystal layer exists in either a planar or focal conic state when no voltage is applied. Applying a low-voltage pulse changes it to a focal conic state. On the other hand, if a high-voltage pulse is applied and held while the layer is in a mixed state of planar or focal conic state, it returns to a planar state.

[0031] The liquid crystal molecules in the cholesteric liquid crystal layer CLC1 are materials that form a helical structure. The cholesteric liquid crystal layer CLC1 reflects circularly polarized light in the same direction as the winding of the helical structure.

[0032] Figures 5 and 6 illustrate the reflection of circularly polarized light by a cholesteric liquid crystal layer. In the example shown in Figure 5, only the strip electrode LE1, the strip electrode UE1, and the cholesteric liquid crystal layer CLC1 sandwiched between the strip electrodes LE1 and UE1 are shown. The cholesteric liquid crystal layer CLC1 has multiple layers P1 to P9, depending on the distance from the strip electrode LE1. In each of the multiple layers P1 to P9, multiple liquid crystal molecules LM are oriented in approximately the same direction. In the example shown in Figure 5, the number of such layers is 9, but this embodiment is not limited to this.

[0033] The white arrows shown for each of the multiple layers P1 to P9 indicate the orientation direction of the liquid crystal molecules LM in each layer. When these orientation directions from layer P1 to layer P9 are connected, they rotate counterclockwise, forming a counterclockwise spiral.

[0034] The direction of rotation of the helix in a cholesteric liquid crystal layer is determined by the structure of the liquid crystal molecules (e.g., the functional groups of the side chains) or the type of chiral agent. More specifically, the absolute configuration of the chiral carbon, the skeleton, and whether the number of spacer atoms to the chiral carbon is odd or even determine whether it reflects right-circularly polarized or left-circularly polarized light.

[0035] As described above, the liquid crystal molecules in the cholesteric liquid crystal layer CLC1 form a counterclockwise helix. As shown in Figures 1 and 6, let LI be the incident light incident on the cholesteric liquid crystal element CLS. Of the incident light LI, left-circularly polarized light CPL, which is in the same direction as the winding of the helical structure, is reflected by the cholesteric liquid crystal layer CLC1. Right-circularly polarized light CPR is transmitted through the cholesteric liquid crystal layer CLC1. The transmitted right-circularly polarized light CPR is irradiated downwards.

[0036] As shown in Figures 1 and 6, the cholesteric liquid crystal layer CLC1 contained in the cholesteric liquid crystal element CLS reflects left-circularly polarized light CPL from the incident light LI. To reflect left-circularly polarized light CPL, the type, ratio, or concentration of the chiral agent, the type and mixing ratio of the polymerizable liquid crystal compound, or the temperature during orientation fixing can be controlled when forming the cholesteric liquid crystal layer CLC1, as described above. As described above, the circularly polarized component in the same direction as the winding direction of the helical structure of the liquid crystal molecules is reflected.

[0037] As shown in Figure 1, the left-circularly polarized CPL light reflected by the cholesteric liquid crystal layer CLC1 is further reflected by the mirror MRR. Through reflection by the mirror MRR, the left-circularly polarized CPL light is converted to right-circularly polarized CPR light. The converted right-circularly polarized CPR light passes through the cholesteric liquid crystal layer CLC1 and irradiates the plant PLT.

[0038] In this embodiment, only right-circularly polarized light, which promotes growth, can be irradiated onto the plant PLT, out of the red and blue light absorbed by the plant PLT. This makes it possible to promote the growth of the plant PLT.

[0039] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of symbols]

[0040] CLC1...Cholesteric liquid crystal layer, CLS...Cholesteric liquid crystal element, CPL...Light, CPR...Light, LCE...Optical control element, LE1...Strip electrode, LM...Liquid crystal molecule, LS...Light-emitting element, MRR...Mirror, P1...Layer, P9...Layer, PLT...Plant, UE1...Strip electrode.

Claims

1. Light-emitting element and Reflectors and, Cholesteric liquid crystal element, Equipped with, The cholesteric liquid crystal chip mentioned above is A first substrate on which a first electrode is provided, A second substrate on which a second electrode is provided, A cholesteric liquid crystal layer sandwiched between the first substrate and the second substrate, Equipped with, The first electrode provided on the first substrate and the second electrode provided on the second substrate are arranged opposite each other via the cholesteric liquid crystal layer. The aforementioned cholesteric liquid crystal layer is It can maintain one of the following states: a state of reflecting light, a state of transmitting light, or a mixed state of the light-reflecting state and the light-transmitting state. The state can be switched by adjusting the voltage between the first electrode and the second electrode that sandwich the cholesteric liquid crystal layer. In the state in which it reflects light, the optical control element transmits right-circularly polarized light and reflects left-circularly polarized light.

2. The optical control element according to claim 1, wherein the light-emitting element includes a first light-emitting element that emits red light and a second light-emitting element that emits blue light.

3. The optical control element according to claim 1, wherein the reflective material is a mirror.

4. The optical control element according to claim 1, wherein the reflective material is a holographic optical element.

Images