Optical member, and light adjusting device employing said optical member

Abstract

In an optical member of the present invention, an optical functional layer having a variable light transmittance is provided between a plurality of light guide plates.　Furthermore, a non-transmissive portion which includes, on a main surface, a light receiving portion for receiving control light causing the light transmittance of the optical functional layer to change, which includes a transmission grating on the light receiving unit, and which absorbs or reflects the control light, is provided between the light guide plates on a path of 0th order light of the control light transmitted through the transmission grating, and as a result, there can be provided an optical member and a light adjusting device in which degradation of the non-transmissive portion can be prevented, and the control light is not visible from either the side from which the control light is emitted or from the opposite side.

Description

Optical member and light control device using the optical member

[0001] The present invention relates to an optical element and a light control device using the optical element, and more particularly to an optical element having an optical functional layer whose light transmittance changes depending on light energy, and a light control device using the optical element.

[0002] Optical elements are known that can change the light transmittance using controlled light such as visible light or ultraviolet light. These optical elements are used in the window glass of vehicles and buildings to color them and adjust the amount of solar radiation entering the interior of a vehicle or room, or to project visible light onto opaque optical elements to display vehicle information or other displays.

[0003] When visible light is irradiated onto the optical element from the outside in order to change the light transmittance of the optical element, the control light becomes visible due to transmission or reflection on the surface of the optical element. Therefore, when the control light is visible light, it is preferable to control the light transmittance of the optical element by irradiating the control light onto the end face of the optical element and guiding the light in the in-plane direction of the optical element.

[0004] However, the window glass of a vehicle or building is often fastened at its end face, making it difficult to irradiate and guide the control light from the end face.

[0005] Although not related to an optical component with variable light transmittance, Patent Document 1 discloses that light is irradiated onto a light guide in the thickness direction, i.e., onto a part of the main surface, and this light is diffracted by a transmission type diffraction grating and a reflection type diffraction grating and guided in the in-plane direction of the light guide.

[0006] Japanese Patent No. 6287487

[0007] In the device described in Patent Document 1, a reflective diffraction grating is provided on the path of zero-order light that has passed through a transmissive diffraction grating, and light irradiated onto a light guide does not pass through to the opposite side of the light guide.

[0008] However, since the reflective diffraction grating is provided outside the light guide, when the optical component is used outdoors, the reflective diffraction grating is prone to deterioration, and over time, the irradiated light passes through the light guide and becomes visible from the opposite side.

[0009] The present invention has been made in consideration of the problems associated with the conventional technology, and its purpose is to provide an optical element that prevents control light from passing through the optical element and being visible from the opposite side even when the optical element is used outdoors, and a dimming device that uses the optical element.

[0010] As a result of extensive research into achieving the above object, the inventors discovered that the above object can be achieved by providing a non-transparent portion inside the optical element that absorbs or reflects control light, and thus completed the present invention.

[0011] That is, the optical element of the present invention includes an optical functional layer having a variable light transmittance and disposed between a plurality of light guide plates, a light receiving section on a main surface for receiving control light that changes the light transmittance of the optical functional layer, a transmission type diffraction grating being disposed in the light receiving section, and a non-transmission section for absorbing or reflecting the control light being disposed between the light guide plates on a path of zero-order light of the control light that has transmitted through the transmission type diffraction grating, thereby diffracting the control light and guiding it in an in-plane direction of the optical element.

[0012] The present invention also provides a light control device including the optical element and a light source that emits a plurality of types of control light having different wavelengths, wherein at least one type of the control light is visible light, and the visible light is incident on the optical element from a light receiving unit provided on a main surface of the optical element via the transmission diffraction grating.

[0013] According to the present invention, a non-transparent portion that absorbs or reflects control light is provided inside the optical element, thereby preventing deterioration of the non-transparent portion and providing an optical element and dimming device in which the control light is not visible not only from the side where the control light is irradiated but also from the opposite side.

[0014] 1 is a schematic diagram illustrating an example of a light control device of the present invention.

[0015] <Optical Member> The optical member of the present invention will be described in detail. The optical member of the present invention includes an optical functional layer having a variable light transmittance between a plurality of light guide plates, as shown in Fig. 1. The optical functional layer changes its optical state between a transparent state and a colored state, or between a transparent state and an opaque state, depending on ultraviolet light or visible light, thereby changing its light transmittance.

[0016] The optical member has, on its main surface, a light receiving portion for receiving control light that changes the light transmittance of the optical function layer, and the light receiving portion is provided with a transmission type diffraction grating.

[0017] The control light incident on the optical member from the light receiving section is scattered inside the optical member by the transmission type diffraction grating, and part of the scattered light is directed in a substantially in-plane direction.

[0018] The control light scattered in a direction larger than the critical angle between the light guide plate and air, i.e., the control light incident on the interface between the light guide plate and air at an angle larger than the angle of incidence at which total reflection occurs at the interface between the light guide plate and air, is totally reflected at the interface due to the difference in refractive index between the light guide plate and air, and does not exit the optical component.

[0019] In the optical member of the present invention, both sides are formed from the same light guide plate, so that the control light undergoes total reflection on both sides of the optical member.

[0020] Specifically, as shown by the arrows in FIG. 1 , the control light reflected at the interface of one light guide plate and directed toward the other light guide plate is incident on and reflected by the interface of the other light guide plate at the same angle as the angle at which it was incident on the interface of the one light guide plate, and is again incident on and reflected by the interface of the one light guide plate at the same angle.

[0021] In this way, the control light incident on the optical member is repeatedly reflected at the interfaces on both sides of the optical member, and is guided in the in-plane direction of the optical member, thereby changing the optical state of the optical function layer.

[0022] Furthermore, since the zeroth-order light of the control light that has passed through a transmission diffraction grating has no diffraction pattern, it is usually transmitted directly to the opposite side of the optical element. However, as shown in FIG. 1 , the optical element of the present invention has a non-transmitting portion on the path of the zeroth-order light of the control light that absorbs or reflects the control light.

[0023] Therefore, even if the control light is visible light, the zero-order light is prevented from being visible from the opposite side of the optical member.

[0024] Furthermore, since the non-transmitting portion is provided between the light guide plates and is not exposed to the outside, the non-transmitting portion is not exposed to wind, rain, or dirt even when the optical element is used outdoors, so deterioration of the non-transmitting portion is prevented, and the control light is not visible not only from the side where the control light is irradiated but also from the opposite side for a long period of time. Note that the non-transmitting portion may be provided on either side of the optical functional layer as long as it is between the light guide plates.

[0025] The optical member preferably has ultraviolet light absorption ability, and the light guide plate itself may absorb ultraviolet light, or an ultraviolet light absorbing layer may be provided between the light guide plates. When an ultraviolet light absorbing layer is provided between the light guide plates, the ultraviolet light absorbing layer is provided on the side where sunlight is incident, usually at a position farther from the transmission type diffraction grating than the non-transmission portion.

[0026] By using a light guide plate or an ultraviolet light absorption layer that has ultraviolet light absorption ability, it is possible to prevent the optical state of the optical function layer from changing due to sunlight, and also to prevent the above-mentioned non-transparent part from deteriorating due to the ultraviolet light contained in sunlight.

[0027] The ultraviolet light absorbing layer is a transparent film containing an ultraviolet light absorber and an ultraviolet light reflector. The ultraviolet light absorber can be a conventionally known ultraviolet light absorber that absorbs ultraviolet light with a wavelength of 400 nm or less, does not absorb visible light, and has little coloring, such as benzophenone derivatives, salicylic acid ester derivatives, triazole derivatives, and acrylonitrile derivatives. Examples of ultraviolet light reflectors include titanium oxide and zinc oxide.

[0028] The non-transmitting portion is not particularly limited as long as it does not transmit the control light, and examples thereof include a black print, black ceramic, a reflective diffraction grating, etc. In particular, a reflective diffraction grating has a fine grating structure formed therein, and if the grating structure is destroyed due to deterioration or the adhesion of dirt, the desired diffraction will not occur, so the optical member of the present invention is highly effective in preventing deterioration.

[0029] The transmission type diffraction grating and the reflection type diffraction grating are preferably blazed diffraction gratings, which exhibit maximum diffraction efficiency at a specific diffraction order, and most of the light amount falls within the desired diffraction order.

[0030] Therefore, the amount of light allocated to orders other than the desired order, such as the zeroth order, is reduced, so that the control light can be efficiently guided in the in-plane direction of the optical element, improving the utilization efficiency of the control light that changes the light transmittance of the optical functional layer.

[0031] It is preferable that the angle of incidence of the control light diffracted by the reflective diffraction grating onto the light guide plate, i.e., the angle between the light of the diffraction order with the highest diffraction efficiency and the direction perpendicular to the interface between the light guide plate and air, is larger than the critical angle between the light guide plate and air.

[0032] By diffracting the control light so that it is incident on the interface at an angle larger than the critical angle between the light guide plate and air, the control light is totally reflected at the interface between the light guide plate and air, so that the control light does not leak out from the main surface of the optical element to the outside, preventing the control light from being visible and improving the utilization efficiency of the control light.

[0033] Furthermore, the optical member preferably has a light leakage prevention portion on its end surface that absorbs or reflects the control light. The light leakage prevention portion prevents the control light from leaking to the outside from the end surface of the optical member.

[0034] In particular, when the light leakage prevention section that reflects the control light is arranged perpendicular to the main surface of the optical element, i.e., the interface between the light guide plate and air, the control light is reflected at the end surface and guided again to the opposite in-plane direction of the optical element, thereby improving the utilization efficiency of the control light.

[0035] An example of the optical functional layer whose optical state changes between the transparent state and the opaque state is a layer containing liquid crystal and azobenzene, and an example of the optical functional layer whose optical state changes between the transparent state and the colored state is a layer containing a photochromic material.

[0036] In the opaque optical functional layer, ultraviolet light causes the azobenzene to change into a cis isomer with a bent three-dimensional structure, causing the liquid crystal molecules to randomly orient, scattering the light and causing the layer to become opaque. Visible light also causes the azobenzene to change into a trans isomer with a planar structure, causing the liquid crystal molecules to orient vertically, allowing light to pass through and becoming transparent.

[0037] In addition, the colored optical functional layer repeatedly changes the state of the photochromic material when irradiated with light, and the wavelength of light absorbed changes depending on the state of the photochromic material, changing between a transparent state and a colored state.

[0038] As the photochromic material, p-type materials that become colored and decolorized by light, and t-type materials that become colored by light and decolorized by heat or light can be used.

[0039] Examples of p-type photochromic materials include diarylethenes and fulgide compounds, and examples of t-type photochromic materials include azovalves and spiropyran compounds.

[0040] The light guide plate may be made of glass, acrylic resin, or the like.

[0041] <Light Control Device> The light control device of the present invention comprises the optical member described above and a light source that emits a plurality of types of control light with different wavelengths that change the light transmittance of the optical functional layer of the optical member.

[0042] At least one type of the control light is visible light, and this visible light is incident on the optical member from a light receiving unit provided on the main surface of the optical member via the transmission type diffraction grating to control the optical state of the optical function layer.

[0043] In addition, if the control light is ultraviolet light, it is not visible, so it does not necessarily have to be incident from the light receiving section of the optical element, and may be directly irradiated from outside the optical element toward the entire surface of the optical function layer in a direction intersecting with the optical function layer.

[0044] The light source can be a light source that emits light of a single wavelength, such as an LED or a semiconductor laser. Since the diffraction angle at a diffraction grating varies depending on the wavelength of the light, if the control light is light of a single wavelength, the control light can be diffracted at a specific angle by the blazed diffraction grating, thereby improving the light utilization efficiency.

[0045] The light control device of the present invention can be used, for example, in vehicle windshields such as automobile front glass and show windows, and can switch between a cloudy screen state on which a visible light image can be projected and a transparent state that allows the viewer to see what is on the other side, and can also adjust the amount of sunlight entering the interior of a vehicle or room by switching between a colored state and a transparent state.

[0046] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0047] Example 1: A transmission diffraction grating 5 with a grating period of 1600 / mm was provided on the surface of one transparent glass plate 3b (refractive index 1.54) to form a light receiving section. An ultraviolet absorbing layer 7 was formed on the entire surface of one side of the other transparent glass plate 3a (refractive index 1.54), and a vertical alignment film (polyimide) was further formed on the entire surface. A reflective blazed diffraction grating 6 (grating period 1000 / mm, γ=15°) with a metal vapor-deposited surface was provided on this transparent glass plate at a location on the path of the zero-order light from the transmission diffraction grating.

[0048] A mixed solution containing 83.65% by mass of a nematic liquid crystal (E44 manufactured by Merck) containing multiple types of liquid crystal molecules, 5.1% by mass of azobenzene molecules represented by the following structural formula (1), 2.9% by mass of a non-photoresponsive chiral compound represented by the following structural formula (2), 0.1% by mass of an electrolyte (cetrimonium bromide; CTAB), 7.5% by mass of a polymerizable monomer represented by the following structural formula (3), and 0.75% by mass of a polymerization initiator (IRGAUCERE819 manufactured by IGM Resins B.V.) was prepared.

[0049]

[0050]

[0051]

[0052] One transparent glass 3b was placed with the light-receiving section 5 on the outside and the other transparent glass 3a with the non-transmitting section 6 on the inside, and the mixed liquid was poured between these transparent glasses while being heated. Light with a wavelength of 420 to 450 nm was irradiated from the side of one light guide plate 3b to polymerize the monomer, forming an optical function layer 4 between the light guide plates. Furthermore, an Ag thin film 8 was formed on the end face to produce the optical element 2.

[0053] A light source 9a emitting control light (visible light) with a wavelength of 450 nm was provided at the light receiving portion of the optical member, and the incident angle was adjusted to 0° with respect to the transmission diffraction grating. In addition, a light source 9b emitting ultraviolet light was provided on the transparent glass 3b side facing the main surface of the optical member, thereby producing the light control device 1 shown in FIG.

[0054] In the above-mentioned light control device, the critical angle of the interface between the transparent glass and air is 42°, the first-order diffraction angle of the transmission diffraction grating is 50°, and the first-order diffraction angle of the reflective blazed diffraction grating is 50°. By illuminating the control light from the light receiving unit, the control light was guided in the in-plane direction, and the optical function layer was clouded. It was also confirmed that the control light from the light source 9a did not leak to the outside.

[0055] Example 2 A light control device was produced in the same manner as in Example 1, except that the reflective blazed diffraction grating was changed to a reflective diffraction grating (grating period: 1600 / mm, first-order diffraction angle: 50°) to form a non-transmitting portion.

[0056] Example 3 A light control device was produced in the same manner as in Example 1, except that the reflective blazed diffraction grating was replaced with a black ceramic print to form a non-transmitting portion.

[0057] The light control devices of Examples 2 and 3 were able to make the optical function layer opaque, and there was no leakage of control light to the outside, as in Example 1. Furthermore, the speed at which the optical function layer became opaque was fastest in the order of Example 1 (reflective blazed diffraction grating), Example 2 (reflective diffraction grating), and Example 3 (black ceramic).

[0058] DESCRIPTION OF SYMBOLS 1 Light control device 2 Optical member 3 Transparent glass (light guide plate) 4 Optical function layer 5 Transmissive diffraction grating (light receiving section) 6 Reflective blazed diffraction grating (non-transmissive section) 7 Ultraviolet absorbing layer 8 Ag thin film (light leakage prevention section) 9a Light source (visible light) 9b Light source (ultraviolet light)

Claims

1. An optical member including an optical functional layer having a variable light transmittance between a plurality of light guide plates, a light receiving section for receiving control light for changing the light transmittance of the optical function layer on a main surface, and a light leakage prevention section for reflecting the control light on an end surface; a transmission type diffraction grating is provided in the light receiving section, Furthermore, a non-transmissive portion that absorbs or reflects the control light is provided between the light guide plates on a path of a zero-order light of the control light that has passed through the transmission type diffraction grating, An optical member which diffracts the control light and guides the control light in an in-plane direction of the optical member.

2. Further, an ultraviolet light absorbing layer is provided between the light guide plates, 2. The optical member according to claim 1, wherein the ultraviolet light absorbing layer is provided at a position farther from the transmission type diffraction grating than the non-transmission portion.

3. 2. The optical member according to claim 1, wherein the non-transmitting portion is formed of a black ceramic or a reflective diffraction grating.

4. 2. The optical member according to claim 1, which is a windshield for a vehicle.

5. An optical member according to any one of claims 1 to 4, A light source that emits a plurality of types of control light having different wavelengths; A light control device, characterized in that at least one type of the control light is visible light, and the visible light is incident on the optical member from a light receiving section provided on a main surface of the optical member via the transmission type diffraction grating.

6. the non-transmitting portion of the optical member is formed of a reflective diffraction grating, The dimming device according to claim 5, characterized in that the angle of incidence of the control light, which is the zeroth order light of the control light that has passed through the transmission type diffraction grating and is diffracted by the reflection type diffraction grating, on the light guide plate is greater than the critical angle between the light guide plate and air.

7. An optical member; A light source that emits a plurality of types of control light having different wavelengths, the optical member includes an optical functional layer having a variable light transmittance between a plurality of light guide plates, A light receiving portion is provided on a main surface thereof for receiving control light for changing the light transmittance of the optical functional layer, a transmission type diffraction grating is provided in the light receiving section, Furthermore, a non-transmissive portion that absorbs or reflects the control light is provided between the light guide plates on a path of a zero-order light of the control light that has passed through the transmission type diffraction grating, the control light is diffracted and guided in an in-plane direction of the optical member, A light control device, characterized in that at least one type of the control light is visible light, and the visible light is incident on the optical member from a light receiving section provided on a main surface of the optical member via the transmission type diffraction grating.