Optical member and dimming device using the 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

Technical Field

[0001] The present invention relates to an optical member and a dimming device using the optical member. More specifically, the present invention relates to an optical member including an optical functional layer whose light transmittance changes by light energy, and a dimming device using the optical member.

Background Art

[0002] Optical members capable of changing the light transmittance by control light such as visible light and ultraviolet light are known. This optical member is used for vehicle or building window glass to color it and adjust the amount of solar radiation incident on the inside of the vehicle or room. Also, visible light is projected onto the clouded optical member to display or present vehicle information.

[0003] In order to change the light transmittance of the above optical member, when visible light is irradiated from the outside toward the optical member, the control light is visually recognized due to transmission or reflection on the surface of the optical member. Therefore, when the control light is visible light, it is preferable to irradiate the end face of the optical member with the control light and guide the light in the in-plane direction of the optical member to control the light transmittance of the optical member.

[0004] However, the end faces of vehicle or building window glasses are often fastened, making it difficult to irradiate and guide the control light from the end faces.

[0005] Although not related to an optical member whose light transmittance changes, Patent Document 1 discloses irradiating light on a part of the main surface in the thickness direction of a light guide, and diffracting this light by a transmission type diffraction grating and a reflection type diffraction grating to guide the light in the in-plane direction of the light guide.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In the case of the one described in Patent Document 1, a reflection diffraction grating is provided on the optical path of the zero-order light that has passed through the transmission diffraction grating, and the light irradiated on the light guide does not transmit to the opposite side of the light guide.

[0008] However, since the reflection diffraction grating is provided outside the light guide, when the optical member is used outdoors, the reflection diffraction grating is likely to deteriorate, and the light irradiated over time transmits through the light guide and is visually recognized from the opposite side.

[0009] The present invention has been made in view of such problems of the prior art, and an object thereof is to provide an optical member in which control light is not visually recognized from the opposite side even when the optical member is used outdoors, and a dimming device using the optical member.

Means for Solving the Problems

[0010] As a result of intensive studies to achieve the above object, the present inventor has found that the above object can be achieved by providing a non-transmissive portion that absorbs or reflects control light inside the optical member, and has completed the present invention.

[0011] That is, the optical member of the present invention includes an optical function layer having a changing light transmittance between a plurality of light guide plates. And it has a light receiving portion on the main surface that receives control light for changing the light transmittance of the optical function layer, a transmission diffraction grating is provided on the light receiving portion, and further, between the light guide plates, a non-transmissive portion that absorbs or reflects the control light is provided on the optical path of the zero-order light of the control light that has passed through the transmission diffraction grating, diffracts the control light, and is characterized by guiding the light in the in-plane direction of the optical member.

[0012] Moreover, the dimming device of the present invention includes the above optical member and a light source that emits a plurality of types of control light having different wavelengths. And at least one of the control lights is visible light, and the visible light is incident on the optical member from a light receiving portion provided on a main surface of the optical member through the transmission type diffraction grating.

Effect of the Invention

[0013] According to the present invention, since the non-transmissive portion that absorbs or reflects the control light is provided inside the optical member, deterioration of the non-transmissive portion can be prevented, and an optical member and a light control device in which the control light is not visually recognized not only from the irradiation side of the control light but also from the opposite side can be provided.

Brief Description of the Drawings

[0014]

Figure 1

Embodiments for Carrying Out the Invention

[0015] <Optical member> The optical member of the present invention will be described in detail. As shown in FIG. 1, the optical member of the present invention includes an optical function layer whose light transmittance changes between a plurality of light guide plates. This optical function layer changes its optical state between a transparent state and a colored state, or between a transparent state and a cloudy state by ultraviolet light or visible light, and the light transmittance changes.

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

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

[0018] Then, the control light scattered in a direction greater than the critical angle between the light guide plate and air, that is, the control light incident on the interface at an angle greater than the incident angle 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 to the outside of the optical member.

[0019] Since both sides of the optical member of the present invention are formed of the same light guide plate, total reflection of the control light occurs on both sides of the optical member.

[0020] Specifically, in FIG. 1, as indicated by the arrow, the control light reflected at the interface of the light guide plate on one side and directed toward the light guide plate on the other side enters the interface of the light guide plate on the other side at the same angle as the incident angle at the interface of the light guide plate on the one side, is reflected, and then enters the interface of the light guide plate on the one side again at the same angle and is reflected.

[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, guided in the in-plane direction of the optical member, and changes the optical state of the optical functional layer.

[0022] Further, since the 0th order light of the control light transmitted through the transmissive diffraction grating has no diffraction pattern, it usually passes through to the opposite side of the optical member as it is. However, as shown in FIG. 1, the optical member of the present invention has a non-transmissive portion that absorbs or reflects the control light on the path of the 0th order light of the control light.

[0023] Therefore, even if the control light is visible light, it is prevented that the 0th order light is visually recognized from the opposite side of the optical member.

[0024] And since the non-transmissive portion is provided between the light guide plates and is not exposed to the outside, even if the optical member is used outdoors, the non-transmissive portion is not exposed to wind, rain, or dirt, so deterioration of the non-transmissive portion is prevented, and over a long period of time, the control light is not visually recognized not only from the irradiation side of the control light but also from the opposite side. Note that as long as it is between the light guide plates, the non-transmissive portion may be provided on either side of the optical functional layer.

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

[0026] By using a light guide plate or an ultraviolet light absorption layer having ultraviolet light absorption ability, not only can the optical state of the optical functional layer be prevented from changing due to sunlight, but also the non-transmissive portion can be prevented from deteriorating due to the ultraviolet light contained in sunlight.

[0027] The above ultraviolet light absorption layer is a transparent film containing an ultraviolet light absorber or an ultraviolet light reflector. The ultraviolet light absorber absorbs ultraviolet light with a wavelength of 400 nm or less and does not absorb visible light. A conventionally known ultraviolet light absorber with little coloring property can be used, for example, benzophenone derivatives, salicylic acid ester derivatives, triazole derivatives, acrylonitrile derivatives. Examples of the ultraviolet light reflector include titanium oxide and zinc oxide.

[0028] The non-transmissive portion is not particularly limited as long as it does not transmit the control light, and examples include black printing, black ceramics, and reflective diffraction gratings. In particular, the reflective diffraction grating has a fine grating structure, and if the grating structure collapses due to deterioration, dirt adhesion, etc., the desired diffraction does not occur. Therefore, the effect of preventing deterioration by the optical member of the present invention is great.

[0029] The above transmission type diffraction grating and reflective diffraction grating are preferably blazed diffraction gratings. The blazed diffraction grating exhibits the maximum diffraction efficiency at a specific diffraction order, and most of the light quantity is within the desired diffraction order.

[0030] Therefore, the light quantity distributed to other orders than the desired order such as the 0th order decreases, so that the control light can be efficiently guided in the in-plane direction of the optical member, and the utilization efficiency of the control light for changing the light transmittance of the optical functional layer is improved.

[0031] The incident angle of the control light diffracted by the reflection diffraction grating onto the light guide plate, that is, the angle formed between the light of the diffraction order with the highest diffraction efficiency and the direction perpendicular to the interface between the light guide plate, air, is preferably 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 it does not leak to the outside from the main surface of the optical member, the control light is prevented from being visually recognized, and the utilization efficiency of the control light is improved.

[0033] Further, the optical member preferably has a light leakage prevention portion that absorbs or reflects the control light at its end face. By having the light leakage prevention portion, the control light is prevented from leaking to the outside from the end face of the optical member.

[0034] In particular, when the light leakage prevention portion that reflects the control light is provided perpendicular to the main surface of the optical member, that is, the interface between the light guide plate and air, the control light is reflected at the end face and guided again in the opposite direction in the plane of the optical member, so that the utilization efficiency of the control light is improved.

[0035] Examples of the optical function layer whose optical state changes between the transparent state and the cloudy state include a layer containing liquid crystal and azobenzene, and examples of the optical function layer whose optical state changes between the transparent state and the colored state include a layer containing a photochromic material.

[0036] The cloudy optical function layer changes to a cis form with a three-dimensional structure in which azobenzene is bent by ultraviolet light, and the liquid crystal molecules are randomly oriented to scatter light and become cloudy. Also, azobenzene changes to a trans form with a planar structure by visible light, and the liquid crystal molecules are vertically oriented to transmit light and become transparent.

[0037] In addition, in the above-described light-shielding optical functional layer, the state of the photochromic material repeatedly changes by irradiating light, the wavelength of the light absorbed changes depending on the state of the photochromic material, and it changes between a transparent state and a colored state.

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

[0039] Examples of the p-type photochromic material include diarylethene and fulgide-based compounds, and examples of the t-type photochromic material include azobenzene and spiropyran-based compounds.

[0040] As the above-described light guide plate, glass, an acrylic resin, or the like can be used.

[0041] <Light control device> The light control device of the present invention includes the above-described optical member and a light source that emits a plurality of types of control lights having different wavelengths and changes the light transmittance of the optical functional layer of the optical member.

[0042] At least one of the above-described control lights is visible light, and this visible light is made to enter the optical member through the above-described transmission diffraction grating from a light receiving portion provided on the main surface of the optical member to control the optical state of the optical functional layer.

[0043] Note that since control light is not visible when it is ultraviolet light, it is not necessarily required to enter from the light receiving portion of the optical member, and it may be directly irradiated onto the entire surface of the optical functional layer in a direction intersecting the optical functional layer from outside the optical member.

[0044] As the above-described light source, a light source that emits single-wavelength light such as an LED or a semiconductor laser can be used. Since the diffraction angle at the diffraction grating changes depending on the wavelength of the light, by making the control light single-wavelength light, the control light can be diffracted at a specific angle by the above-described blazed diffraction grating, and the utilization efficiency of the light is improved.

[0045] The dimming device of the present invention can be used, for example, for vehicle windshields such as the front glass of an automobile or a show window, and can switch between a turbid screen state in which a visible light image can be projected and displayed and a transparent state in which the opposite side can be visually recognized, or can switch between a colored state and a transparent state to adjust the amount of solar radiation incident on the inside of the vehicle or the room.

Example

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

[0047] [Example 1] On the surface of one transparent glass 3b (refractive index 1.54), a transmission diffraction grating 5 with a grating period of 1600 / mm was provided to form a light receiving portion. Further, an ultraviolet absorption layer 7 was formed on the entire surface of one side of the other transparent glass 3a (refractive index 1.54), and a vertical alignment film (polyimide) was formed on the entire surface. On this transparent glass, at a location on the path of the 0th-order light from the above transmission diffraction grating, a reflective blazed diffraction grating 6 (grating period 1000 / mm, γ = 15°) with a metal vapor-deposited on the surface was provided.

[0048] A mixed solution containing 83.65% by mass of nematic liquid crystal (manufactured by Merck: E44) containing a plurality of 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-light-responsive chiral 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 (manufactured by IGM Resins B.V.: IRGAUCERE819) was prepared.

[0049]

Chemical formula

[0050]

Chemical formula

[0051]

Chem.

[0052] One of the transparent glasses 3b was arranged such that the light-receiving part 5 was on the outside, and the other transparent glass 3a was arranged such that the non-transmissive part 6 was on the inside. The above-mentioned mixed solution was injected while heating between these transparent glasses. Light with a wavelength of 420 to 450 nm was irradiated from the side of one of the light guide plates 3b to polymerize the above-mentioned monomer, and an optical functional layer 4 was formed between the light guide plates. Further, an Ag thin film 8 was formed on the end face to fabricate the optical member 2.

[0053] A light source 9a of control light (visible light) with a wavelength of 450 nm was provided at the light-receiving part of the above-mentioned optical member, and the incident angle was adjusted to be 0° with respect to the transmission type diffraction grating. Further, a light source 9b that emits ultraviolet light was provided on the side of one of the transparent glasses 3b facing the main surface of the optical member to fabricate the light control device 1 shown in FIG. 1.

[0054] The critical angle of the interface between the transparent glass and air of the above-mentioned light control device is 42°, the first-order diffraction angle of the transmission type diffraction grating is 50°, and the first-order diffraction angle of the reflection type blazed diffraction grating is 50°. By making the control light incident from the light-receiving part, the control light was guided in the in-plane direction, and the optical functional layer could be clouded. Also, it was confirmed that there was no leakage of the control light from the light source 9a to the outside.

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

[0056] [Example 3] A light control device was fabricated in the same manner as in Example 1, except that the reflection type blazed diffraction grating was changed to a black ceramic print to form the non-transmissive part.

[0057] The light control devices of Examples 2 and 3 could cloud the optical functional layer and there was no leakage of the control light to the outside, similar to Example 1. Also, the clouding speed of the optical functional layer was fast in the order of Example 1 (reflective blazed diffraction grating), Example 2 (reflective diffraction grating), and Example 3 (black ceramic).

Explanation of Signs

[0058] 1 Light control device 2 Optical member 3 Transparent glass (light guide plate) 4 Optical functional layer 5 Transmission type diffraction grating (light receiving part) 6 Reflective blazed diffraction grating (non-transmissive part) 7 Ultraviolet absorption layer 8 Ag thin film (light leakage prevention part) 9a Light source (visible light) 9b Light source (ultraviolet light)

Claims

1. An optical member comprising an optical functional layer with a varying light transmittance between a plurality of light guide plates, having a light receiving portion on a main surface for receiving control light that changes the light transmittance of the optical functional layer, and having a light leakage prevention portion on an end surface for reflecting the control light, wherein a transmission type diffraction grating is provided in the light receiving portion, furthermore, between the light guide plates, a non-transmissive portion that absorbs or reflects the control light is provided on the path of the zero-order light of the control light transmitted through the transmission type diffraction grating, characterized in that the control light is diffracted and guided in the in-plane direction of the optical member.

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

3. The optical member according to claim 1, characterized in that the non-transmissive portion is formed of a black ceramic or a reflective diffraction grating.

4. The optical member according to claim 1, characterized in that it is a vehicle windshield.

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

6. The non-transmissive portion of the optical member is formed of a reflective diffraction grating, and the incident angle of the control light diffracted by the reflective diffraction grating of the zero-order light of the control light transmitted through the transmission type diffraction grating to the light guide plate is greater than the critical angle between the light guide plate and air. The dimming device according to claim 5, characterized in that.

7. A dimming device having an optical member, and a light source that emits a plurality of types of control light with different wavelengths, wherein the optical member includes an optical functional layer with a varying light transmittance between a plurality of light guide plates, has a light receiving portion on a main surface for receiving control light that changes the light transmittance of the optical functional layer, a transmission type diffraction grating is provided in the light receiving portion, furthermore, between the light guide plates, a non-transmissive portion that absorbs or reflects the control light is provided on the path of the zero-order light of the control light transmitted through the transmission type diffraction grating, characterized in that the control light is diffracted and guided in the in-plane direction of the optical member. A light control device, characterized in that at least one of the control lights is visible light, and the visible light is incident on the optical member from a light receiving portion provided on a main surface of the optical member through the transmissive diffraction grating.

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